eChapters

Due to inadequate intakes of vitamins and minerals, half of the world's population suffers from micronutrient malnutrition. An adequate amount of wholesome as well as diverse foods are required for the proper growth and development. In addition to calories requirements, these foods should provide various nutrients. In India, ~70% of children do not get the required calories either due to lack of enough food or diverse food. This indicates that these children are also incapable of fulfilling their protein, minerals and vitamins requirements. Diets that lack diversity can be deficient in certain nutrients. Due to the micronutrient composition of the soil of a region, or because of the intrinsic insufficiency of the normal diet the staple foods of some region can lack particular nutrients. The individual plant foods are often deficient in certain nutrient components due to the varying level and composition of food nutrients in different food crops. Some crops are rich in one component but low in other. For example; legumes are usually high in protein, but deficient in essential amino acids like methionine whereas, wheat and rice are rich in carbohydrates but contain little essential amino acid such as lysine, iron, and lack provitamin A. Relying on a single food crop as major staple source of nutrients thus will not attain a nutritionally complete diet and result in malnutrition and deficiency diseases, which often occur in populations of developing countries, mainly due to poverty. Globally, over one billion people are undernourished and food security is a major issue with the world's population forecast reaching to nine billion by 2050.

16.1 Introduction

Food safety is most important issue in today's global environment. To safeguard food supply is a very difficult and challenging responsibility, as a consequence of which the world's largest food companies, retailers, and manufacturers have placed very high food safety standards. Although the safety of food has improved exponentially but progress is uneven and food borne outbreaks due to microbial contamination, pesticides, antibiotics chemicals and toxins are common in many countries. International trade statistics (2007) by World Trade Organization (WTO) reported that Europe has accounted for 46% of world exports of agricultural products, where food represents 80% of agricultural exports. The trading of contaminated food among countries increases the risk for outbreaks and consequently, health risks due to microbial pathogens in food are of major concern to all governments.

Biosensors are an important option in the agricultural and food sectors to control production processes and ensure food quality and safety by dependable, fast and cost effective methods. Biosensors have plenty of advantages over conventional analytical tools since they offer advantages in size, cost, inherent specificity, selectivity, rapid response, accuracy and sensitivity. Food microbiologists are always in search of rapid and reliable automated systems for the detection of biological activity. Biosensors provide sensitive, miniaturized systems that can be used to detect unwanted microbial activity or the presence of a biologically active compound, such as glucose or a pesticide. Immunodiagnostics and enzyme biosensors are two of the leading technologies that have had the greatest impact on the food industry. The use of these two systems has reduced the time for detection of pathogens such as Salmonella to 24 hour and has provided detection of biological compounds such as cholesterol or chymotrypsin. The another useful application for biosensors, is detection of genetically modified organisms (GMO), since several countries have laws regulating the commercialization of GMO products and their derivatives. Biosensors are also useful in the implementation of hazard analysis and critical control points (HACCP) plans by verifying process developments and correcting errors in due time. There is joint application of Biosensor technologies and nanotechnologies in many food and agricultural applications such as the development of nano-scale tools for biosafety, nanoscale compounds for food packaging, and nano-sensors for pathogen detection in animals and plants. These are helpful tools in the detection and control of potential food contaminants by the agricultural and food industries.

15.1 Introduction

Color of food is the most sensitive part of any commodity as it is the one of the organoleptic characteristic to be noticed and one of the main ways of visually assessing a food before it is consumed. The people associate certain colors with certain flavors and the color of food can influence the perceived flavor in anything from confectionary to beverages. For this reason, food manufacturers add dyes to their products. Sometimes the aim is to simulate a color that is perceived by the consumer as natural, such as adding red coloring to glace cherries, but sometimes it is for effect, like the green ketchup that was launched by Heinz in 2000. If the flavor of a food product is inconsistent with the color, the flavor can often be perceived incorrectly, for example an orange flavored drink colored green could be perceived to taste of lime. In addition, the color of a food substance is important indicator of its freshness. While all of us are aware that food with bright or unnatural colors likely contains food coloring but only few people know that natural foods such as oranges and salmon are sometimes also dyed to mask natural variations in color. The color variation in foods throughout the seasons and the effects of processing and storage often make color addition commercially advantageous to maintain the color expected or preferred by the consumer. Some of the primary reasons include:

14.1 Introduction

Proteins are the substances formed from nitrogen containing amino acids and are principle structural components of body tissues and muscle. In addition, they are used to produce various hormones, enzymes and hemoglobin in human body. Due to the shift from agricultural to electronics and other fast paying industrial development, most of the countries around the world, ceased to be self-sufficient in their food production in particular protein, which is necessary to satisfy their optimum food demands. The biotechnology development and its usage to agriculture have brought hope to them. The need for food by modernization of agriculture has gained much attention throughout the world. However, the necessity for exploring unconventional and non-agricultural means of food production, especially of proteins rich food, cannot be over-emphasized due to the tremendous growth of human populations in several regions of the world. In addition to this, the importance of protein in food nutrient cannot be put aside because its shortage causes various malnutrition problems and the most lethal malnutrition problem is Protein-Energy-Malnutrition (PEM). The United Nations Food and Agriculture Organization estimates that nearly 870 million people of the 7.1 billion people in the world, or one in eight, were suffering from chronic undernourishment in 2010-2012. There are 925 million people undernourished in developed countries (FAO October, 2010). This situation has created a demand for the formulation of innovative and alternative proteinaceous food sources having high nutritional value. These sources have to be non-competitive with food for human consumption, economically feasible and locally available. This demands a search for new protein sources, with high nutritional value, economically feasible and locally available. Use of microbes as a food source is one of the biotechnological innovations that will certainly increase the availability of affordable protein in the world to solve the global food and feed problems.

In recent decades there has been an increased interest in the industrial production of microbiological protein for use in both human and animal nutrition. The main reason behind it is that there has been the shortage of low cost protein sources in view of the increasing human population and living standards, resulting in famine in some parts of the world and increased demand for animal protein in others.

13.1 Introduction

A surfactant or surface-active agents are the compounds that lower the surface tension between the two liquids or between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, foaming agents and dispersants. Surfactants are normally organic compounds that are amphiphilic, meaning they contain both hydrophobic groups or hydrophilic groups. Therefore a surfactant contains both a water insoluble component and a water soluble component. Surfactant will diffuse in water and adsorb at interfaces.

The interfacial free energy is the minimum amount of work required to create that interface and the interfacial tension between two phases is determined as the interfacial free energy per unit area. The interfacial (or surface) tension is also a measure of the variance in nature of the two phases meeting at the interface (or surface). The greater the dissimilarity in their natures, the greater the interfacial (or surface) tension between them. A surfactant is therefore a substance that changes the amount of work required to expand those interfaces. Surfactants usually act to reduce interfacial free energy.

Surface active agents in the form of emulsifiers have a long history of use and are widely used in many products being used in everyday life. An extensive basic research is required to understand the reason of instability and methods to prevent the breakdown of emulsions. Emulsifiers can function as dough conditioners by improving tolerance to variations in flour quality, better gas retention resulting in lesser yeast requirements, increased uniformity in cell size, a finer grain, more resilient texture and improved slicing. Also, the characteristics of freshly baked bread like soft crumb can be retained longer, if the appropriate emulsifiers are added. Commonly used surface active agents in bread production are propylene glycol mono- and diesters, polyoxyethylene sorbitan monostearate, ethoxylated mono- and diglycerides, succinylated monoglycerides and Diacetyl tartaric acid, esters of monoglycerides. Cookie characteristics like top grain, volume and spread ratio can also be improved. Here surfactants used are sodium stearoyl fumarate, sucrose fatty acid esters, sodium stearoyl lactylate, sorbitan fatty acid esters, polysorbates and ethoxylated monoglycerides. In dairy products like Ice cream surface active agents play some important functions like to improve fat dispersion and control fat agglomeration, facilitation of fat– protein interactions, facilitate air incorporation, give smoother texture due to smaller ice crystals and air cells, increase resistance to shrinkage, improve melt-down and reduce whipping time. In candy products, the elimination of “bloom,’’ i.e., the transition of fat crystals is a key reason for the addition of surface active agents. In mixtures of triglycerides, surfactants like sorbitan esters (Spans) and ethoxylated sorbitan esters (Tweens) can control product viscosity in chocolates and in cream fillings and modify the crystal structure. Surface active agents have been utilized in the production of meat analog products also. In margarine, Emulsifiers fulfil several functions like modification of crystal structure in the vegetable fat, assistance in emulsion formation and antispattering. Here, a mixture of citric acid monoglycerides and monoglycerides or lecithin can be used. The properties and mode of action of these chemical surfactants is discussed in the following sections.

12.1 Introduction

Micronization is a size reduction in which particles are reduced down to micrometer resulting in particle-size distribution is less than 10 microns. Acceleration of particles has been involved for particle-to-particle impact or impact against a solid surface. Micron technology is an emerging technology which has a great potential in nutraceuticals and functional foods. By increasing the surface area per unit mass, compared with larger-sized particles of the same chemistry, tiny particles are made more biologically active. A lot of attention has been gained by micronization in food research and development. Functional properties, surface areas and structures gets altered by reduction in particle sizes of different materials (e.g., metal salts, metal oxides, chitosan and organic compounds) by micronization or nanotechnology to micro- or nano-sizes and bring some new applications in the academic world as well as in food industry.

They absorb a large concentration (10-40 wt %) of C0₂ that either swells the polymer or melts it at a temperature below (10 to 50 °C) it’s melting/ glass transition temperature hence, this technique is useful for micronization of especially for polymers. Active substrate(s) in a polymer or other carrier substance can be used with suspensions for micronization process. In manufacturing advanced pharmaceuticals, coating materials, micro sensors, polymers and many other chemicals particle design has been gaining importance. Formulation homogeneity and control particle size can be improved by micronization. Moreover, bioavailability of poorly soluble APIs (active pharmaceutical ingredient) by increasing particle surface area and accelerating dissolution rates can also be improved. Because of the high impact velocities possible as a result of particle acceleration in a fast gas stream, fluid energy mills are used for micronization. Particle velocities in a jet mill are in the range of 300 to 500 meters per second, compared to 50 to 150 meters per second in a mechanical impact mill, in many industrial fields like food technology, pharmaceuticals, catalysts, pigments, and biopolymers, for example, are some categories of products that can be used as micro-sized particles, micronized powders are of great interest. High-temperature reactions that require high energies, on jet milling that is characterized by low efficiencies and mechanical stress, and on liquid solvents precipitation that has a poor control on particle size and can pollute the product comes under the traditional techniques for producing micronic powders. Generally, the control of the powder size and the span of its distribution are still very approximate. In recent years, many supercritical fluids-based techniques have been developed for the production of micronic and nanometric particles. Some particular properties of gases at supercritical conditions such as enhanced solubilization modulation and its power, large diffusivities, organic solvent reduced operation, and the connected possibility of controlling powder size and distribution resulted from this process. Important characteristics of powders like particle size and size distribution have significant effects on dissolution properties, flowability and release kinetics. Therefore, particle engineering is the most important step during processing of powdered foods. Lower micrometer range and sizes are needed for many applications particles with special requirements. Processes like jet milling, pearl milling or high pressure homogenization are used for micronization.

11.1 Introduction

Phytosterols or plant sterols are bioactive plant constituents having similar chemical structure and biological functions as cholesterol (cholest-5-en-3b-ol), but differ in their side chain configuration. They are non-nutritive compounds with chemical structure differing from that of cholesterol only by minor modifications like in the structure of their side chain by a methyl or ethyl group at C-24. Sitosterol and campesterol have an ethyl and a methyl group at C-24, respectively (Fig. 11.1). Phytosterols present a tetracyclic ring and side chains linked to C-17 that differ according to sterol compound same as cholesterol, to which they resemble structurally as well as biosynthetically. Saturated form of sterols referred to as stands, occurring in small amounts, mainly in cereals are represented by the absence of the double bond at the D5 position. Phytosterols represent a part of the broad group of isoprenoides and are 28- and 29-carbon atom steroid alcohols naturally occurring in plants. Phytosterols and phytostanols are triterpene compounds, found ubiquitously in plants which can only be synthesized by plants, whereas humans and animals obtain them from their diet.

10.1 Introduction

Food safety and quality are the two important factor which results in consumer food choices. Nowadays consumers are demanding food which is safe and of high quality in terms of nutrition due to a healthier life style. Food safety and quality are the terms used interchangeably. Food safety refers to all those hazards, that make food injurious to the health of the consumer and it is not negotiable. Food quality includes attributes that influences the product's value to the consumer. This includes both negative and positive attributes; negative attributes includes spoilage, contamination, discoloration, off-odours and positive attributes include colour, flavour, texture and processing method of the food. This distinction between safety and quality has implications for public policy and influences the nature of the food control system. Food control is defined as a mandatory regulatory activity which provides consumer protection and ensures food is safe, wholesome and fit for human consumption during production, handling, storage, processing, and distribution.

Despite the huge efforts made by the food safety authorities and industries, food safety still remains a critical issue. In food industries, producers have to satisfy both safety and quality criteria for their products to the consumer. Food processors have multiple options in terms of different quality and management systems, they have to choose the most appropriate one for its specific activity and should establish, document and implement effective systems in the processing area for managing quality and safety of the product. Over the past few decades, food-borne illnesses have raised great concern about the safety of food. Considerable steps are taken by the food processor for understanding and managing the risks of airborne diseases. Among various systems, Hazard Analysis and Critical Control Point (HACCP) is effective tool which focuses mainly on controlling hazards to ensure the production of safe and wholesome food. For maintaining the safety and increasing the shelf life of food, traditionally it has been preserved by thermal processing, freezing, salting and drying. But nowadays consumers are demanding convenient, innovative, fresh foods, including new "minimally processed" products. To meet consumers' expectations in the 21^st century, the food industries are implementing novel technologies whose purpose will be two fold: 1) to provide the new quality attributes demanded by consumers; and 2) to ensure the all important and often expected assurance of food safety. The novel technologies will include various minimally processed technologies like high pressure processing (HPP), pulsed electric field (PEF), ohmic heating, dielectric heating, microwave heating, ultrasound, modified atmosphere packaging (MAP) and cleanroom technology. Among these cleanroom technology have attracted great attention for maintaining the safety and quality of the food products as because it doesn't have any effect on the nutritional quality of the food being processed, it maintains the hygienic condition in the processing area, remove contaminants from the processing area and clean air in the processing area which in turn results in safe food product. The main objective of cleanroom technology is to eliminate airborne contaminants from the humans and/or from the environment. An air curtains and a positive air pressure is maintained in the processing unit using filtered air. Production personnel will use the special clothing which is preferred for cleanroom to reduce the contamination from both air- and human-borne microorganisms. In this chapter we will discuss about cleanroom technology, its historical background, its classification, layout of cleanroom, air handling, personnel and its clothing, regulations in cleanroom, and its application in food industries.

9.1 Introduction

Food quality and safety are central issues in food economics today. A number of developed countries (EU, UK, US) has imposed a number of new regulations to track food products across the supply chain which is forcing the companies to invest in new automated approaches for their implementations. These solutions facilitate better process efficiency with more productivity, quality control in production lines, lower manufacturing costs with higher profit margins, and also help to achieve improved presentation as customers request. The high labour costs in developed countries make cost-cutting inevitable to remain competitive production. The growth in products packaged for the market, the increasingly strict hygiene regulations, the need to reduce risks at work, cut costs, and control product quality are all calling for the development of technologies that enable robots to be used for these tasks. In fact, robotics has a great opportunity in this industry. But the variation in physical properties of various food products and the necessity to avoid damaging them, make it necessary to seek flexible handling solutions for a wide range of products.

The robotics industry is looking into a bright future. As per the report given by the Statistical Department of International Federation of Robotics (IFR), it was projected that between 2014 and 2016 worldwide robot sales will increase by about 6% on average per year. Ten years ago, global sales figures were hovering around 80,000. So, three key factors for the boom - factory modernization, increases in production capacity and rising demand from a number of emerging markets.

8.1 Introduction

Electron Microscopes were developed due to the limitations of Light Microscopes which are limited by the physics of light to 500x or 1000x magnification and a resolution of 0.2 micrometers. In the early 1930’s this theoretical limit had been reached and there was a scientific desire to see the fine details of the interior structures of organic cells (nucleus, mitochondria etc.). This required 10,000x plus magnification which was just not possible using Light Microscopes. The Transmission Electron Microscope (TEM) was the first type of Electron Microscope to be developed and is patterned exactly on the Light Transmission Microscope except that a focused beam of electrons is used instead of light to see through the specimen. It was developed by Max Knoll and Ernst Ruska in Germany in 1931. The first Scanning Electron Microscope (SEM) debuted in 1942 with the first commercial instruments around 1965. Its late development was due to the electronics involved in scanning the beam of electrons across the sample. Electron microscope has been a valuable tool in the development of scientific theory and it contributed greatly to biology, medicine and material sciences. This wide spread use of electron microscopes is based on the fact that they permit the observation and characterization of materials on a nanometer (nm) to micrometer (µm) scale. Electron Microscopes are scientific instruments that use a beam of highly energetic electrons to examine objects on a very fine scale. This examination can yield information about the topography (surface features of an object), morphology (shape and size of the particles making up the object), composition (the elements and compounds that the object is composed of and the relative amounts of them) and crystallographic information (how the atoms are arranged in the object). A scanning electron microscope (SEM) is a type of electron microscope that produces images of a sample by scanning it with a focused beam of electrons. The electrons interact with atoms in the sample, producing various signals that can be detected and that contain information about the sample surface topography and composition. SEM can achieve resolution better than 1 nanometer. The combination of higher magnification, larger depth of focus, greater resolution, and ease of sample observation makes the SEM one of the most heavily used instruments in research areas today.

7.1 Introduction

Food processing has become one of the most competitive sectors in recent years. With increasing consumers’ demands, food industry needs to keep updating technology. These efforts are focussed at improving the organoleptic quality and nutrition of food and improve its keeping quality. This drives the industry to look for newer technologies which include new products as well as new processes. Some of the new processing technologies include non-thermal processes such as high pressure processing, pulsed electric fields and ultrasound processing. Advanced thermal processing techniques such as ohmic heating, inductive heating, extrusion and infrared heating have also been developed. Innovative methods for improving food quality through irradiation, removal of heat and moisture from food are now available. Newer packaging techniques now help to improve shelf-life and attractiveness of the food products and cater to the biodegradability of the packaging material. Hence, there is abundance of new products that have now become part of our daily life.

Food nanotechnology has its long history when the first step of revolution in food processing and improvement in quality of foods was introduced by Pasteur to kill the spoilage bacteria (1000 nm). Later, Watson and Crick’s model of DNA structure, which is about 2.5nm, opened the gateway of applications in biotechnology. Nanotechnology is defined as the design, production, and application of structures, devices, and systems through control of the size and shape of the material at the nanometer (10^-9 of a meter) scale. Nanotechnology is one such technology that has the potential to revolutionize the food industry. Taniguchi first used nanotechnology in 1974 to describe production technology at ultrafine dimensions. The word “nano” means “dwarf” in Greek and one nanometer is equivalent to 10^-9 m. Objects of this scale are not visible through the human eye or the ordinary optical microscope. A nanometer (nm) sized particle measures one billionth of a meter. A human hair measures 80,000 nm while a DNA strand is 2.5 nm wide whereas a protein chain is 5nm in diameter. Nanotechnology can be applied to develop nanoscale materials, controlled delivery systems, contaminant detection and to create nanodevices for molecular and cellular biology. Nanotechnology may be defined as the understanding and management of matter at dimensions of roughly 1-100 nanometers. Unique behavior of matter at the nanoscale enables novel applications. Nanoscale science, engineering, and technology can be used for imaging, measuring, modeling, and manipulating matter at this length scale. Range of sizes of nanomaterials in the food sector and their relative position on nanoscale/microscopic scale are listed below.

6.1 Introduction

Consumer demand, regulatory guidelines and economic power of the consumer as well as ascertained profitability stimulated the need of novel food processing techniques. The concept of “fresh”, “natural”, or “organic” food also led to the development of environmentally sound and resource efficient food processing technologies. Thermal processes have been used for food preservation since a long time. These are not very energy efficient and can change the phase of food from fresh to cooked as well as it can alter the nutritional and sensory qualities. Thus, the quest for energy conservation by the manufacturers to reduce carbon footprint of the processes involved in food processing and preservation as well as to fulfill consumers’ requirement for fresh-like quality food have given rise to the development of innovative non-thermal food processing technologies i.e. ionizing radiation, high-intensity light pulses, high isobaric pressure, electric or oscillating magnetic fields, as well as pulsed electric fields (PEF).

Application of electric energy in food processing started in the early 1900s. In the beginning, electrical pasteurization inactivated microorganisms by increasing the temperature of samples by means of an electrical resistance (ohmic heating). Milk was the first electrically pasteurized product. In the late 1940s, electric fields were used to increase the permeability of fruits to facilitate the subsequent extraction of juices. The PEF technology as a non-thermal process is very effective for inactivation of microorganisms, increasing the pressing efficiency, enhancing the juice extraction, and for intensification of the food dehydration and drying process. The main effect of PEF technology is based on the phenomena that biological membranes are punctured under the influence of external electrical impulses. This process is often referred as non-thermal, since the structural damage to membranes is implemented at very low temperature compared to the conventional heating process. The PEF process is considered to be energy efficient because the electric energy is released in short pulses, thus total energy requirement is much lower than other continuous preservation technologies. The microbial inactivation can be achieved at ambient or moderately elevated temperatures by the application of short-bursts of high intensity electric fields to liquid foods flowing between two electrodes or to semi-solid/ solid food between some specialized electrode and treatment systems. Due to chemical/physical properties and presence of electrical charge, the liquid foods (e.g. milk or fruit juices) had different conductivity, which results in variable flux of electrical current through the food systems.

5.1 Introduction

Food is the basic requirement of every living being and it provides physical, mental as well as emotional satisfaction. Globally, there are many food enterprises which provide this basic necessity across the nations irrespective of nature of origin and climatic condition. Food companies are required to provide products at certain quality parameters so as to maintain the uniformity in the food system. Hence, food quality can be defined as a total of traits and criteria which characterize food as regard to its nutritional value, sensory value, convenience as well as the safety for a consumer’s health. Food quality is the quality characteristics of food that is acceptable to consumers. This includes external factors as appearance (size, shape, colour, gloss and consistency), texture, and flavor; factors such as grade standards and internal (chemical, physical, microbial). Due to the various food risks, all over the world the quality regulation authorities have intensified the efforts to improve food quality. Some of the quality related systems are obligatory by law while other is voluntary which are to be implemented by the various food chain members.

Many companies are forced to improve safety and quality of their products by implementing the quality and safety assurance and management system because of growing consumers’ expectations and concerns as regards food quality and safety.

In order to attain maximum profit and decrease the flaws, a new system was developed and followed by various companies all over the world. This new system is known as Six Sigma. The application of this system has the capability to reduce the losses considerably by reviewing the process parameters and increasing the profit exponentially. It constitutes a systematic approach to assure that food products have particular traits at any stage of production and distribution.

4.1 Introduction

The purpose of processing the food is to make it safe and healthy for human consumption. The term food processing refers technologically anything, which transforms raw ingredients into consumer ready products, with the aim of stabilizing food products by preventing or reducing deteriorative changes in quality. The objective of food manufacturers is to develop, modify and employ those processing technologies that retain or create desirable sensory qualities in food and eliminate or reduce undesirable changes due to processing.

The purpose of food processing is to increase the shelf life of food before spoiling (preservation); to remove, destroy or inhibit pathogens and toxins (food safety); to change flavor, texture, aroma, color or form (variety); to reduce preparation times and make food more portable (convenience); to restore and/or raise nutrient levels in food (nutrition).The various food processing methods used extensively in food industry include physical (high temperature, freezing, chilling, dehydration, packaging), chemical (control of storage gases, reduction of water activity, pH, addition of chemical additives or spices) preservation methods.

Traditionally, food preservation has been associated with thermal treatments alone or in combination with biochemical or chemical methods. For example, the thermal processing of milk is done various thermal treatments viz. at 63^oC for 30 min for low temperature long time (LTLT), 72^oC for 15 seconds for high temperature short time (HTST) pasteurisations and up to 140^oC for a few seconds for ultra high temperature (UHT) treatment. However, such thermal treatments effectively reduce level of microorganisms but in long-term preservation, it may lead to losses of desired organoleptic attributes and destruction of temperature liable nutrients and vitamins. The limitations involved with thermal processing has been overcome by employing chemical preservation, cool chain management and process hygiene in the formulation and production of food products.

3.1 Introduction

Energy comes in many forms like chemical, radiant, mechanical, electrical, nuclear etc and can transform from one type to another. Energy can also be transferred or moved from one object to another. Electromagnetic (EM) radiation is a form of energy that can take many forms, such as radio waves, microwaves, X-rays and gamma rays even sunlight is also a form of EM energy. Visible light is a small portion of the EM spectrum, which contains a broad range of electromagnetic wavelengths.

Electromagnetic waves, a self –propagating transverse radiation, are created when an atomic particle, such as an electron, is accelerated by an electric field, causing it to move. The movement produces oscillating electric and magnetic fields. The electric and the magnetic components of the wave are perpendicular to each other and also perpendicular to the direction in which wave is travelling in a bundle of light energy called a photon. Photons travel in harmonic waves at the fastest speed possible in the universe: 186,282 miles per second (299,792,458 meters per second) in a vacuum, also known as the speed of light. There are three important characteristics of the electromagnetic radiation, its frequency, amplitude and speed (Figure 3.1).

2.1 Introduction

Food is one of the complex systems involving many constituents such as carbohydrates, lipids, proteins, vitamins, minerals and other phytochemicals. These all constituents are not present in the same relative proportion in every type of food and thus the foods are categorized and valued according to the presence of these constituents as protein rich foods, fat rich foods, etc. The specific type of food is in abundance with only one or at most two of these constituents and rest of the bulk is not valuable, commercially. So, if these active constituents which are present in the tissue surrounding inactive matrix, are separated, it is of great benefit with respect to increased purity, nutritive value, functional properties, reduction in volume, easy handling and transportation. On contrary some valuable food items contain undesirable constituents generally referred as anti-nutritional factors. Removal of these anti-nutritional factors enhances the food value and commercial utilization. Hence, the separation of phytochemicals and removal of anti-nutrients from the food matrices can be easily carried out by using a unit operation called as extraction.

Extraction involves the separation or isolation of active/desirable components of complex system viz., plant and animal tissues from the rest of inactive/undesirable components by using suitable means such as solvent or mechanical structure. The basic principle involved in the extraction process is partitioning of different components in accordance with the extracting agent. For example, in mechanical extraction, the partitioning is due to pressure and screen/apperature size where as in case of solvent extraction, the portioning of components from mixture takes place due to particular solubilizing power of solvent used.

1.1 Introduction and Background

In present scenario, the word “extrusion” refers to a process by which dry or semi-moist ingredients with varying in-barrel moisture are forced through varying barrel temperature, screw speed and screw configuration through a die opening of the desired cross section. In other words, extrusion is predominantly a thermo-mechanical processing operation that combines several unit operations, including mixing, coating, kneading, venting, shearing, heating, forming, partial drying or puffing, depending on the material and equipment used.

The origins of extrusion are in the metallurgical industry, where in 1797 Joseph Bramah patented the first extrusion process, wherein a piston driven device was used for making seamless lead pipes. The present understanding of extrusion technology and the developments or improvements in machine design are largely due to research carried out by the plastics industry. In food industry, this technology is in use since 1930 and its popularity is increasing continuously due to its efficiency, continuity and sustainability. In beginning, sausage extruders were developed in the nineteenth century as simple forming machines. One of the original developments which laid the foundation of the food extrusion was the use of pasta press termed as “cold extruder” in mid 1930s. Furthermore, in the late 1930s, General Mills, Incorporation., Minneapolis, MN, USA, first used a single screw extruder in the manufacture of ready-to-eat (RTE) cereals. Later in 1970s, twin screw extruders were used for the manufacture of moist pet-foods. Twin screw extruders were also adapted from polymer industry, as rising food quality and limitations of single screw extruders were demanding a more versatile process for the newer and higher quality products. After 1970s, the extrusion processing with simultaneous use of heat was popularized as a versatile and highly energy efficient with negligible wastage process. In all these years, number of changes has been noted in the extruder design such as changes in screw design, barrel design and also material used for the manufacture of these materials. Barrel liners availability along with already available segmented screws could further add more economics to the process and increased equipment lifetime. For better wearing characteristics, a number of screw elements of different materials are being used in addition to standard nitrided steel for customized processing needs, such as corrosion and wear resistant surface coated steels, stainless steel, satellite welded and bimetallic HIP (Hot Isostatic Press). JBL Feedscrews Limited, a UK based company recently introduced tungsten carbide coated screw in conjunction with a compatible bimetallic barrel. Likewise, a number of options for barrel metallurgy are available to withstand the higher internal pressure and temperature. Barrels lined with hard cobalt based alloy, typically Xaloy, to give abrasion and chemical resistance are also in use, although, the most common material is carbon steel with a nitride interior. Similarly, steam heated or jacketed barrels were used earlier for cooking purpose which gradually replaced by the electric induction heating elements. These HTST cooking extruders are versatile, highly productive and energy efficient processing machines. They can use a wide variety of raw materials and formulations to produce products with increased shelf-life and convenience.

For looking into the biosafety in research laboratories, agriculture and other food producing industries it is important to look into the numerous strains of lactic acid bacteria that are associated with food systems and are capable of producing bacteriocin or antibacterial proteins with activity against foodborne pathogens such as Listeria monocytogens, Staphylococcus aureus and Clostridium botulinum. Recently considerable attention has been given on the identification of these proteins and their biochemical properties including spectrum of activity, production conditions, purification procedures, aminoacid composition and mode of action. Advances in genetic engineering have facilitated the characterization of proteins at genetic level, providing information about protein synthesis, structure and cloning of bacteriocin genes into other organism. One problem in the use of bacteriocin in their applications as bio-preservatives is the emergence of resistant population. The understanding on the mechanism of resistance to bacteriocins is limited which limits the application in biopreservation. Much of the work on bacteriocin has been done under controlled laboratory conditions without the presence of adventitious microbial population. More research is needed to determine the efficacy of bacteriocin producing organisms and bacteriocins which are stable under commercial conditions. Foodborne illness is a major international problem and an important cause of reduced economic growth. The contamination of the food supply with the pathogens and its persistence, growth, multiplication and/or toxin production

Food safety scientifically describes various methods of handling, preparation and storage of food to prevent any foodborne illnesses. However, it is important to check the safety between industry, market and the consumer. From the food industry to the market the practices relating to food labeling, food hygiene, food additives and pesticide residues are important to be looked into and the policies on biotechnology. The governmental imports and exports needs to be given proper guidelines. Certification systems and Inspection for foods need to be installed which should be clean and corruption free. When all this is properly considered the food could be safe in the market. This may allow for safe delivery and safe preparation of the food for the consumers. Many diseases are transmitted by food which serves as a growth medium for bacteria and cause food poisoning. In the developed countries it has been observed that there are many intricate standards for food preparation. However, in the developing countries the availability of adequate safe water itself is a question. It is possible to prevent food poisoning to 100%. An ordinance and code regulation in US (1943)was given.

Henderson et al., (2010) have studied the different aspects of food regulation. The authors have looked into the perceptions of Australian consumers’ who is and should be responsible for food safety. Forty-seven participants were interviewed as part of a larger study on trust in the food system. Participants associate food governance with government, industry and the individual. While few participants can name the national food regulator, there is a strong belief that the government is responsible for regulating the quality and safety of food. Personal responsibility for food safety practices was also identified. Little evidence is found in the politicisation of food, reflecting a level of trust in the Australian food governance system that may arise from a lack of exposure to major food scares. According to Wood (1990) the marketing of food service program in an Ohio district is directed toward the students and also at the community, school administrators, teachers, and employees. Students are encouraged to follow a healthier way of eating.Jones (1998) studied the role of food safety in the food chain from farm to fork. In response to growing threat of food-borne illnesses the federal government had launched the Food Safety Initiative. A key element is the Hazard Analysis Critical Control Point’s system (HACCP). Under this it has been designed to make everyone in the food-delivery chain to be responsible for ensuring a safe food supply.

Josephson (1977) studied the effects of food irradiation and sterilization. In radiation sterilization of food (radappertization) the food is exposed in sealed containers to ionizing radiation at absorbed doses which are high enough (25-70 kGy) to kill all organisms of food spoilage and public health significance. Radappertization is analogous to thermal canning for enhancing the shelf stability. In dry products the radappertization process requires the food to be heated to an internal temperature of 70-80°C (bacon to 53°C) to inactivate autolytic enzymes which catalyze spoilage during storage without refrigeration. In order to reduce off-flavors and odors, undesirable color changes, and textural and nutritional losses from exposure to the high doses of irradiation the foods are vacuum sealed and irradiated frozen. Radappertozed foods have the characteristic of fresh foods prepared for eating. Irradiation can be a good substitute for some chemical food additives such as ethylene oxide and nitrites which are toxic, carcinogenic, mutagenic or teratogenic either wholly or in part. Till now, there is no evidence of any adverse effects of radappertization on the foods. Extensive research has taken place towards the space food. During the planning of Apollo missions, Space Food NASA Technical Reports Server (Space Food NASA Technical Reports Server, NTRS ,1994 ) conducted trials including freeze drying.

Jay et al., (1995) and Joerger et al., (2003) have written the role of bacteriocins as an alternate to antibiotics. Bacteria produce bacteriocins which are proteinaceous in nature or peptidic toxins. These inhibit the growth of similar or closely related bacterial strain(s). There are different types of bacteriocins which are classified based on the producing strain, common resistance mechanisms and mechanism of killing. Ahmad et al., (2013) have isolated antifungal compound for food preservation. Martin et al., (2018) and Batish et al., (1997) found antibacterial compounds from fungus. Mahboubi et al., (2019) studied the potential of Zataria in IBS. There are bacteriocins from gram-positive bacteria known as the colicins, the microcins and the bacteriocins from Archaea (Cascales et al., 2007). The bacteriocins from E. coli are called colicins (formerly called ‘colicines,’ meaning ‘coli killers’). These have been studied widely. Earlier called colicin V and is now known as microcin V. It is very small and is produced and secreted in a different manner than the classic colicins. Adrienne et al., (2016) have studied the colicin resistance.

A process control system that identifies the hazardous points in the food production process is known as HACCP (Hazard Analysis Critical Control Point). It puts into place many stringent actions to prevent any hazards from occurring. In any food process if there is strict monitoring and controlling steps, the chances for hazards are minimum. Today, HACCP is an integral part of modern food industry that identifies and controls the major food risks. These are like microbiological, chemical and physical contaminants. These can also be practiced at home scale by checking proper storage, handling, cooking and cleaning procedures. These steps have resulted in industries taking greater responsibility for and controlling the food safety risk factors. This helps in better consumer protection, agriculture, the food processing industries and promotes domestic and international food trade.

The temperature of food storage is important. Below 4⁰C the food pathogens do not grow. Above 60⁰C some colonies begin to die. However, almost all die at 71⁰C. How hot is the food served is important for food safety. The size of the piece is important to how quickly it will cook all the way through. The smaller the piece the faster it will cook. Large or thicker pieces take a longer time to be cooked. Otherwise cooking for a longer time is better so that pathogenic microorganisms do not grow. In case of a thicker piece the color must be checked inside to outside after cooking which should be consistent. If the meat has the bone, check the color/temperature closest to the bone in the thickest part. In case of meat the contamination usually gets introduced while butchering and the practices used. The street food on a cart is perhaps the most contaminated as it has some level of bacteria in it. The meat in the decorated malls also has pathogenic bacteria. The environment plays a very pivotal role which can recontaminate the food even after proper cooking. The amount of harmful pathogens keeps growing in number with the passage of time. Fresh from the grill is the best, an hour or two is not ideal, half a day or overnight could make a person sick. Due to the reason that consumers do not know the time and temperature of cooking it is important to eat food which is freshly prepared.

Due to the globalization of the food supply there has been a need to strengthen food safety systems in and between the countries. In this regard the World Health Organization (WHO) has promoted efforts in improving the food safety from farm to plate which started on World Health Day, 7 April 2015. The World Health Day 2015 slogan was “From farm to plate, make food safe”. The informal food production and marketing system is still strong in most countries of the South-East Asia Region, for the enforcement of food safety regulations. Traditionally, the preferences have been for hot and well-cooked food. These habits are partially responsible for preventing foodborne infections. In many countries street food has become very popular as it is cheap. Hygienic conditions are improving, provided that potable water supply and clean facilities are ensured by municipal authorities. Many waterborne and diarrhoeal diseases could be prevented with the introduction of bottled drinking water. The awareness and education on food safety by the consumers has strengthened in the enforcement of food standards. This has improved the hygienic practices and has helped in the prevention of foodborne illnesses. The “WHO Five keys to safer food” serves as the basis for educational programmes to train food handlers and educate the consumers. These help in preventing the foodborne illnesses. The important points are to keep food surfaces clean, washing of all utensils, plates and cutlery, keeping the raw food separate from the cooked food. Cooking food thoroughly to the appropriate temperature, keeping food at safe temperatures, both for serving and storage and using safe water and raw materials.

Even after public concern the scientists feel that the GMO foods are quite safe. According to them the genetically-engineered crops are very safe to eat as much as the non-GE of the same crop. According to them the environment has improved by reducing the use of pesticides. GMO stands for genetically modified organism. Soy, corn, or other crops are very common as GM crops which are made by genetically engineered DNA. Many have come to the conclusion that GM foods are safe, healthy and sustainable. However, some people are against them. There are many benefits of GM crops like less water or pesticides to be used. Genetically engineered crops fight diseases to save the foods. At the same time the industries/ farmers that grow them are also benefitted. These foods have higher nutritional profiles, both in the US and abroad like corn which is one of the most prominent GMO foods. Soy is found in tofu, vegetarian products, soybean oil, soy flour and many other products. The other major crops taken for genetic modification are Papayas, Canola and Cotton. For dairy products a lot of work is being done on the genetic engineering of animals in a big way. This is going to be the most intractable environmental challenge of the 21^st Century. Presently, around 92% of the U. S. corn (GE), 94% of soybeans and 94% of cotton are genetically engineered.

When certain disease-causing bacteria or pathogens contaminate food, they can cause foodborne illness, often called “food poisoning”. Foods that are contaminated may not look, taste or smell any different from foods that are safe to eat. Salmonella, Campylobacter, Listeria and Escherichia coli are common bacteria causing foodborne illness. Some foodborne illnesses are mild where most people get better within a few days, but illness can sometimes be more severe and fatal. Bacillus cereus can form heat resistant spores. On cooking the food with these spores the heat resistant toxin is left at room temperature. Reheating or lightly cooking the food does not destroy these toxins. Most types of foodborne illnesses cause symptoms like nausea, vomiting, watery diarrhea, abdominal pain and cramps. Fever and/or the presence of blood or mucus in the stool are signs of bacterial infection that may require a medical consultation. Proper food handling is vital to prevent most foodborne illnesses and diseases. WHO has given keys towards safer food which should be followed. Unsafe food containing harmful bacteria, viruses, parasites or chemical substances, causes more than 200 diseases which range from diarrhoea to cancers. Foodborne and waterborne diarrhoeal diseases kill around 2 million people worldwide annually, including many children. A single foodborne bacterium can grow into more than two million bacteria in just seven hours under the right conditions. Foodborne pathogen called Listeria sp. can survive and sometimes grow on foods being stored in the refrigerator. Hepatitis A virus can cause long-lasting liver disease and spreads typically through raw or undercooked seafood or contaminated raw produce. It is estimated that more than 250 million people worldwide suffer food allergies. The boiling temperature (smoke point) of cooking oil is above 200 °C. The boiling point of water is 100 °C.

According to the World Health Day (WHO,2015) food contamination happens when food are corrupted with another substance. It can happen during the process of production, transportation, packaging, storage, sales and cooking process. The contamination can be physical, chemical and biological. Faulde et al., (2013) studied the infection caused to patients by mothfly

Food adulteration is an unethical and often criminal malpractice. It is very common in countries of the South-East Asia region. It frequently occurs where informal food production and marketing services are predominant and enforcement of food regulation is weak. The prohibited substances are either added or used to partly or wholly substitute healthy ingredients. This creates the impression of freshness in old food artificially. Adulteration in food is usually done for financial gain. The high target is spices due to the demand and also their high price. Sometimes it can happen due to lack of proper hygienic conditions of processing, storage, transportation and marketing. The consumer is either cheated financially or becomes a victim of illness or disease. In case, the consumers take a lot of precautions at the time of purchase of such products it would help them in avoiding the purchase of such adulterated food. The whole spices: Dirt, dust, other seeds; chili powder: brick powder, salt powder or talc, powder. In ghee/butter: vegetable ghee, animal fat, mashed potato, sweet potato, etc. ; ice cream and beverages:saccharin; honey: jaggery, sugar syrup. Food contaminants are not added to the foods. They are present in foods as a result of the production (crop farming, animal husbandry and aquaculture), manufacture, processing, preparation, treatment, packing, packaging, transport or holding of such food or as a result of environmental contamination. Usually it includes the presence of harmful chemicals or microorganisms in food, which if consumed can cause several debilitating illnesses. Many times, unknowingly, the contamination may occur during the production, processing, storage and marketing.

In this century the usage of plastics had become very common. However, it is important to know as to what kinds of plastics are used for food handling and storage and the health hazards caused by using it. It has been observed that plastic packaging plays a significant role for the enhanced shelf life and in the ease of storage and cooking for many foods. Some kinds of plastic materials which are widely used for handling and storage of food and water include polyethylene terephthalate (PET). It is used in soft drinks, water, sport drinks, ketchups, salad dressing bottles, peanut butter, pickle, jelly and jam jars. This plastic is strong, heat resistant, resistant to gases and acidic foods. It can be transparent or opaque. It does not leach any chemicals that are suspected of causing cancer or disrupting hormones and can also be recycled.

Usage of High density polyethylene (HDPE) has been found to be common in milk, water, juice bottles, yogurt, margarine tubs, grocery, trash and retail bags. High-density polyethylene is stiff and strong but is not heat stable (it melts at a low temperature). It does not leach any chemicals that have a role in causing cancer or disrupting the hormones. HDPE can be recycled. Low-density polyethylene (LDPE) is used into making films of various types, some bread and frozen food bags and also in the making of squeezable bottles. Low-density polyethylene is relatively transparent. Many of the films are not heat stable either and may melt the food in case it is touching it. However, polypropylene (PP) is more heat resistant, harder, denser and more transparent than polyethylene and is therefore used for heat-resistant microwavable packaging and sauce or salad dressing bottles. Polycarbonate is clear and heat resistant. It is also durable and often used to make refillable water bottles and sterilisable baby bottles, microwave ovenware, eating utensils, plastic coating for metal cans. Tiny amounts of bisphenol A are formed when polycarbonate bottles are washed with harsh detergents or bleach (sodium hypochlorite). At high levels of exposure, bisphenol A is potentially hazardous as it mimics the female hormone estrogen. In addition, polystyrene (PS) and polyvinyl chloride (PVC) are also used during food material transportation and handling in supermarkets. Modern food safe plastic bags are plasticizer-free which do not leach harmful chemicals into the food during cooking.

Today, organic and local foods are preferred as they use less pesticides or fertilizers. However, these foods, like others, can be exposed to harmful bacteria during the growing and harvesting process. The farmers and distributors must use good sanitary practices to minimize food contamination. Consumers should cook food properly. The street food vendors are a traditional and indigenous fast food approaching in most countries of the South-East Asia Region. As these are economical they cater to millions of consumers. Among safe street foods there are many contributing factors that are associated with the safety of street food. WHO had conducted a survey in 1993 covering 100 street foods in 100 countries around the world. It revealed that the major health threat comes from raw and undercooked food, infected food handlers and inadequate hygiene practices in processing and storing such food. If the street food is cooked well and is served hot, then the chances of food poisoning is less. The water quality, hygienic conditions and the level of cleanliness especially in the summer season are the major factors for food poisoning. However improvements in physical infrastructure and hygienic conditions are growing as consumers are also demanding quality food. Michael et al., (2017) have looked into organic versus conventional foods.

According to Futter (2001) it is very important the way we cook our food. If the cooking is inadequate it causes food poisoning. While cooking there can be cross contamination starting from raw foods. It includes hands or utensils which can cause food poisoning. Most foods, especially meat, poultry, fish and eggs should be cooked thoroughly to kill most types of food poisoning bacteria. Generally the food should be cooked to a temperature of 75 °C or hotter. When food is cooked, it should be eaten promptly, kept hotter than 60 °C or cooled, covered and stored in the fridge or freezer. Some people are more at risk from food poisoning than others. In order to buy safe food in the market like buying pre-cut produce as a half a watermelon or cut veggies from a salad bar, it is important to choose items that are refrigerated or surrounded by ice. They must be kept in separate bags. FDA (2019) has studied the contamination in lettuce. Shopping at a farmer’s market is a great way to get locally-grown, fresh fruit, vegetables, and other foods. However, safety of these produce needs to be checked. Many markets have their own food safety rules and vendors must comply with them along with the government regulations. Fruits and vegetables must be washed thoroughly under running water just before eating, cutting or cooking. Fruits and vegetables must never be washed with soap or detergent or using commercial produce washes. Even if it has to be peeled before eating, it is still important to wash it first. Any bacteria present on the outside of items like melons can be transferred to the inside when it is cut or peeled. They should be refrigerated within two hours after preparation. The juice or cider must be treated (pasteurized) to kill harmful bacteria. Pregnant women, children, older adults and people with weak immune systems should drink only pasteurized or treated juice. Raw milk can harbor dangerous microorganisms like Salmonella, E. coli, and Listeria. World India (2017) has looked into the food regulations. These can pose serious health risks. Pregnant women, older adults and people with weakened immune systems are at higher risk for illness caused by Listeria. One source for these bacteria is soft cheese made from unpasteurized milk. It is vital to check the label to make sure that it is made from pasteurized or treated milk. Make sure that eggs are properly chilled at the market. FDA requires that untreated shell eggs must be stored and displayed at 45°F. While buying eggs it needs to be ensured that the eggs are clean and the shells are not cracked. Meat should be properly chilled even in the market and kept in closed coolers with adequate amounts of ice to maintain cool temperatures. If it is brought in an insulated bag or cooler during transit it is very beneficial to keep the quality. It should be always kept separately from your other purchases, so that the juices from raw meat (which may contain harmful bacteria) do not come in contact with produce and other foods. Essays (2018) have written a very comprehensive overview of food safety.

It is a discipline of science that describes handling, preparation and storage of food that can prevent food-borne diseases. When there are two or more cases of a similar illness from the ingestion of the same common food it is known as a food-borne disease outbreak (FSN, 2018). In order to avoid potential health hazards, food safety is very important. This needs safety between industry, market and the consumer. For food safety the labelling on food material is vital. This includes the origin of food, steps taken for food hygiene, food additives, pesticide residues, policies on biotechnology, food guidelines for the management of governmental import, export inspection and certification systems for foods. The food should be safe in the market with safe preparation and delivery of the food for the consumer. Foegeding et al., (1996) have done an assessment of risk factors with food borne pathogens.Warnock et al., (2007) have reported intervention to food safety.

When pathogens are in the food they may be transmitted to the consumer. It may result in an illness or death of the person or other animals. The pathogens include bacteria, viruses, molds and fungus. These multiply in the food medium. Joon et al., (2012) have found pathogenic bacteria in meat products of Korea. The developed countries have high intricate standards for the preparation of food; however, in the developing countries there are less standards and enforcement of the standards which are followed. Apart from food another major source of infection is water, which is very critical in spreading many diseases. It is possible to prevent food poisoning if good water is used for all purposes. However, it becomes difficult as in the food supply chain a large number of persons are involved apart from the fact that pathogens can be introduced into foods no matter how much precautions are taken. Cowden (2000) has studied the notification on food poisoning to improve health. Frenkel et al., (2015) studied the amount of wastes from food processing industries.

Human beings have been concerned about the concept of food safety since time immorial. Around the globe there has been major improvement in food safety management in the last twenty years. Looking into the progress made on the ways to make food safe and how to make them free from pathogens, this book, will explain food hygiene, the journey of research been taken in food safety till date and the challenges that we are going to face in future to ensure food safety and its wholesomeness. It also includes the role and responsibilities of the various sectors of society, namely governments, food industry, consumers and academia.

In the beginning of the twentieth century many modern food safety policies have been established. In the packing of meat and in food processing industries a lot of work has been done (Sinclair 1906). Another second generation policy includes the outbreak in the United States in early 1990s’ of pathogen E. coli O157:H7 and the BSE scandal of the late 1990s in the UK Lopman et al., (2003) have discussed on viral outbreak in europe. Currently, the crisis has come due to the economic and technological transformations which have taken place in food and the food supply system. As these changes have many health risks the public is very concerned. Therefore, the control forms of safety regulation and food safety laws have come into the picture. These policies include continuous line inspection, visual product inspection and detailed specification of approved hygiene practices. There is a need of a public health-focused policy which works towards the preventive integrated management of foodborne hazards from farm to table. This includes the use of modern science based risk management tools which will increase the efficiency accurately towards public health. A lot needs to be worked out for better implications. Current efforts to modernize food safety policy around the world are being worked out by the use of risk analysis and cost-benefit analysis in public administration and also the quality management in industry. The role of public economics plays an important role in food safety policies. For the social benefits the policy makers need to take decision on the costs and strengthening of the risk assessment. Today there are globalized markets and this can influence the health globally. Emerging economies like China are industrializing and urbanizing rapidly like that of Europe and North America.

Fermentation

The term fermentation is loosely used to denote any process in which microorganisms are involved, regards of whether or not the organism is growing in the presence of molecular oxygen. Thus, it can be defined as 'an ATP generating metabolic process in which organic compounds serve both as electron donor (becoming oxidized) and electron acceptor(becoming reduced). Energetically, fermentations are poor energy yielding process and products have lower energy content then the substrates. Since there is no net oxidation in fermentation, the number of molecules of C, H and O remain the same in products as in the substrate.

14.1 Culture from Urine

Infection of urinary tract due to microorganisms affect patient of all age group and both sex., and they vary in severity from an unsuspected infection to a condition of severe systemic disease. Urine is a ordinarily excellent culture medium for the multiplication of common pathogen of urinary tract. Most bacteria found in the urine are due to contamination of skin flora during passage and they tend to increase greatly, exceeding 10⁶/ml. When the bacterial count exceeds 10⁵ per ml of urine it indicates significant bacteriuria and is indicative of a urinary tract infection. Infection of the urinary tract may be limited to a single tissue/ organ or they may spread upward and involve the entire urinary system. Escherichia coli is the most common urinary tract pathogen. Pseudomonas aeroginosa causes another important urinary tract infection, which is characterized by blue green pus. Cystitis (inflammation of urinary bladder), Pyelonephritis (inflammation of the kidney) are permanent diseases of urinary tract.

Urinary tract infections are generally characterized by bacteriuria, bacteria in the urine. Quantitative microbiological assay of urine can identify the probable pathogen. For this purpose, calibrated loop- direct streak method and pour plate method are routinely used. Now-a-days commercially prepared special plastic device called the urine dip slide and diagnostic urine–culture called Bacturcult is being used for isolation and identification of microorganisms from genitourinary tract infections. The Bacturcult is a sterile disposable plastic tube coated with a special medium on its inner side for detection and identification of bacteriuria.

With increasing industrialization, water sources available for consumption as potable water are being adulterated with industrial, animal and human wastes. As a result water has become a formidable factor in disease transmission. Polluted water usually contains large amount of organic matter which forms nutritional base for growth and multiplication of microorganisms. Usually the water with non-pathogenic organisms, like autotrophs and saprophytic heterotrophs, are not of major concern, but presence of intestinal contaminants of fecal origin are of great concern. These pathogens are responsible for intestinal infection such as bacillary dysentery, typhoid fever, cholera and paratyphoid fever.

The detection of all the intestinal pathogens on a routine basis would be a tedious and difficult task, however, it would be easy to demonstrate the presence of some of the nonpathogenic intestinal organisms like Escherichia coli and Streptococcus faecalis. These are always found in intestine but their detection confirms the contamination of water with fecal material. Such organisms are also called pollution indicator.

Viruses are smaller than bacteria and require living cell for their growth. They can be detected through the bacteria to which they parasitise. Viruses are associated with both eukaryotes as well as prokaryotes and contain either DNA or RNA; only few have both DNA and RNA.

Viruses that infect bacteria are called bacteriophage. They consist of head or capsid and a tail. The head may be round, oval, polyhedral and is made up of proteins while tail is hollow and provides an exit for nucleic acid to enter in bacterial cell. The tail also helps in attachment to the cell wall surface of bacteria. After injection of the nucleic acid into bacteria they multiply and form large number of bacteriophage particles which cause lysis of the bacterial cell wall releasing many bacteriophages. Phages that cause lysis are known as lytic phages and that do not cause lysis are called temperate phage. The most common lytic phage is E.coli – a coliphage.

Identification of enteric bacilli is of prime importance for controlling intestinal infections. This can be achieved by preventing contamination of food and water by a group of bacteria belonging to family – Enterobacteriaceae which are found in the intestinal tract of human beings and lower mammals. The microorganisms of this family are short, gram negative, non spore forming bacilli. Such common enteric bacteria are a) pathogens such as species of Salmonella and Shigella b) occasional pathogens like species of Proteus and Klebsiella and c) normal intestinal flora like species of Escherichia and Enterobactor.

10.1 Transformation of E. coli by electroporation Principle

Preparation of electro-competent bacteria is considerably easier than preparing cells for transformation by chemical methods. Bacteria are simply grown to mid –log phase, chilled, centrifuged, washed extensively with ice cold buffer containing 10% glycerol. DNA may be introduced immediately into the bacteria by exposing them to a short high voltage electrical discharge. Alternatively, the cell suspension may be snap frozen and stored at-70^oC for 6 months before electroporation, without loss of transforming efficiency.

Since E.coli cells are small, they require very high strengths (12.5- 15KV cm^-1) for electroporation as compared to those used to introduce DNA into eukaryotic cells. Electroporation is temperature dependent and is best carried out at 0-4°C.

The highest efficiency of transformation is obtained when the concentration of input DNA is high (1-10 μg/ml) and when the length and intensity of the electrical pulse are such that only 30-50% of the cells survive in the procedure. Under these conditions, as many as 80% of the surviving cells may be transformed. Higher frequencies of transformation (colonies/ molecules input DNA) are obtained when the DNA concentration is low (?10pg/ml).

The method outlined in this protocol is followed with most strains of E.coli and with plasmids <15kb in size. However, substantial variation in the efficiency of transformation between the strains of E. coli. has been reported. As in case with chemical transformation, linear plasmid DNAs introduced into E.coli by a pulsed electrical discharge transform very efficiently from 10 to 1000 fold but less efficiently than the corresponding closed circular DNA – perhaps because the exposed terminal of linear DNA are susceptible to attack by intracellular nucleases.

Antibiotics are produced by some true bacteria, actinomycetes and fungi that destroy or inhibit the growth of other microorganisms. Some antibiotics are synthesized or modified in the laboratory; however, their origins are always in living cells.

9.1 Assay of Antibiotics

Soil serves as the major repository of microorganisms some of which produces antibiotics. Four groups of soil microorganisms viz; Streptomyces, Bacillus, Penicillium and Cephalosporium represent three microbial types, namely, actinomycetes, true bacteria and molds respectively.

Following procedure may be applied to isolate antibiotic-producing microorganisms from soil:

Our exposure to wide variety of chemicals has increased markedly in the recent past. Most of these compounds are mutagenic as well as potential carcinogens. Emphasis is being laid to develop method for detection of environmental carcinogens so that their use can be avoided.

Despite the fact that mammalian cell structure and human enzymatic pathways differ from those in bacteria, the chemical nature of DNA is common to all organisms; this permits the use of bacterial test systems for rapid detection of possible mutagens.

The Ames test which was developed by Bruce Ames in 1970, at the University of California, U.S.A. is a mutational reversion assay employing several special strains of Salmonella typhimurium, each of which has a different mutation in the amino acid histidine biosynthesis operon.

S. typhimurium, the indicator organism, used in this test is the mutant strain that cannot synthesize histidine (His^-), lack the enzyme to repair DNA so that mutation shows up readily and has leaky cell wall that permit the rapid entry of chemicals. In addition, this S. typhimurium strain carries mutation enhanced plasmid, the combined effect of these characters increase the sensitivity of the organism to mutagenic treatments.

The term growth for bacteria and other microorganism usually refers to changes in the total population rather than an increase in size or mass of an individual organism. As the mechanism of conservation and dissipation of heat generated during metabolism lacks in bacteria, the enzyme system in bacteria gets directly influenced by temperature. The purpose of studying the bacterial growth curve is a) to become familiar with the population growth dynamics of bacterial culture and b) to plot a growth curve and determine the generation time of bacterial culture.

A number of methods are now available for measuring bacterial growth. Some important ones are

1)By colony counting or cell counting

2)By weighing the cells

3)By cell activity (turbidity method)

The science dealing with the measurement of size of any microscopically visible microorganism is known as micrometry which is based on the principle of physics. Before measuring a cell, the diameter of the microscopic field must be established by means of optic devices, namely an ocular micrometer and a stage micrometer.

a)Ocular micrometer : It is a circular disc that is placed in the eyepiece. The disc is graduated in to several small divisions marked from 0 to 100.It is placed inside the eyepiece of the microscope. The distance varies according to the objective of the microscope which can be easily determined by using a stage micrometer.

b)Stage micrometer : It is a glass slide graduated in 1 mm. Again 1mm is divided into 10 large divisions and 100 small divisions (10 x 10 = 100 divisions). These divisions are equally placed therefore 1 small division is equal to 0.01 mm or 10 μm.

Generally microorganisms are so small and colourless in their natural state that it becomes difficult to observe them clearly under microscope. Stains and dyes, which are colouring agents, are used by biologist for better understanding of the morphological and anatomical structures of the organisms under study. Stains are prepared with great care and specification to get satisfactory result, while dyes are not as exacting in their characteristics.

Dyes are of two types, natural and synthetic. The natural dyes are used for histological purposes, whereas the synthetic dyes for bacterial stain. Usually dyes which are derivatives of cyclic compound benzene of benzole, are prepared from one or more substances found in coal-tar, and so are called coal-tar dyes. Chemically dyes are organic compounds containing both chromophore and auxochrome groups linked to benzene rings. Chromophore group provides the compounds the property of colour and thus benzene containing chromophores are called chromogens. It has no affinity to combine with fibres or tissue and as such not called dye. For being a dye, compound should contain an auxillary group which provides the compounds the properties of electrolytic dissociation.

The dyes may be acidic, basic or neutral. The acidic dyes are eosin, acid fuchsine and picric acid whereas the basic dyes are safranin, methylene blue, crystal violet etc. The acidic dyes ionize to give the dye portion of molecule a negative electrical charge. They are salts of sodium, potassium, calcium, magnesium etc. The basic dyes ionize to give the dye portion of molecule a positive electrical charge and are salts of chlorides, sulphates or acetates.

4.1 From Soil

Soil contains varied group of microorganisms such as fungi, bacteria, actinomycetes, algae and protozoa. The type of nutrients available, moisture, temperature and pH of the soil determine the nature of microbial population in soil. Different laboratory techniques for isolation of microorganisms have been detailed in chapter-III. These are used in particular for the isolation of specific type of microorganisms. All the techniques adopted are just to segregate the pathogens/ microorganisms from the mixture of microbial population present in nature.

(a) Isolation of Fungi

Soil contains large number of fungi and constitutes a major place of microbial population. They can be isolated in pure form by following the methods given below:

Under natural habitats microorganisms usually grow in mixed populations containing several species. This is really a problem for microbiologists because a single type of microorganism can not be studied adequately in a mixed culture. In laboratories these populations can be separated into pure cultures. The pure cultures contain only one type of organism and are thus suitable for studying the cultural, morphological and biochemical characters of an individual species. In the present days there are several ways of developing pure cultures in laboratories. Some of which are as follows:

Microorganisms, being ubiquitous, are found in soil, air, water, food, sewage, on body surfaces as well as on degrading and decomposing substances. Their survival and continued growth mostly depend on an adequate supply of nutrients and favourable growth environments. The culture media (nutrients) consisting of chemicals support the growth of microorganisms in a given condition. They are devised in such a way that the organism should get all the nutritional requirements. These are usually prepared in laboratory by weighing and dispensing the individual ingredients. Generally, the common media contain both inorganic and organic nutrients; however, for the cultivation of large number of microorganisms, specialized media are required.

Basically the culture media are of three types: (1) Natural, (2) Semi synthetic and (3) Synthetic.

Microbiology is a branch of science dealing with the study of organisms which are too small to be seen clearly by unaided eye. Roughly the organisms with a diameter of 0.1mm or less, which can not be seen by the human eyes unaided, come under the domain of microorganisms.

Thus, the laboratory work dealing with the microorganisms needs special care to avoid infection and infusion for maintaining good health. In fact all microorganisms should be treated as potential pathogens. Thus, for working with microorganisms aseptic techniques must be followed by students as well as by the laboratory assistants and teachers.