eChapters

14.1 Introduction

The increasing human population and changing life styles have resulted in a huge demand for processed and packaged foods. As a result of this demand, large amounts of water, air, electricity and fuel are consumed on a daily basis for food processing, transportation and preservation. Although not one of the most heavily polluting, the food industry does contribute to the increase in volume of waste produced [1]. There is an increasing pressure from regulatory bodies through incentives, legislation and financial penalties to minimize waste generation and encourage adoption of eco-friendly options for waste management. Nanotechnology is a panacea for food waste management.

13.1 Introduction

Hospitality industry is the second largest industry in the world. It is well diversified and can be chosen as per the interest. Hospitality management involves planning, organizing, directing and controlling human and other resources within the different segments of hospitality industry i.e. lodging, restaurant, travel and tourism, institutional management, recreational management, meeting and convention planning industries. Although, these all are separate but related segments of the hospitality industry and are interrelated to provide good and efficient services to the guests and users. Hospitality industry provides services which are need oriented and differ in various parts of the world as per regions and the traditional styles.

The first building created specifically for hotel was ‘City Hotel’ with 73 rooms at 115 Broadway, New York in 1794. Pallonjee Pestonjee established the very first western-style hotel in India, “The Bristol Hotel” in Mumbai in 1840. According to the report of the department of Tourism, Government of India, at the end of the year 2004, there were 167 Five star hotels with approx. 28,900 rooms, whereas 126 Four star hotels, with 8,831 rooms [2]. To expedite the ongoing process of classification/re-classification of functioning hotels in one to three star categories, five Regional Committees have also been set up in Delhi, Mumbai, Kolkata, Guwahati and Chennai to conduct inspection [3].

12.1 Introduction

Man is the most beautiful of all God’s creations and like man, his environment too is beautiful with rivers to quench his thirst with sweet water, atmosphere to provide him oxygen, land and fire to provide him food. Primitive man ate uncooked food and lived in caves. Soon he learnt the use of firewood for cooking of raw meat and provided the first instance of ‘Pollution from food processing’ in history. As man shifted from one place to another, this sort of living never polluted the environment. But as the man ascended the ladder of civiliz ation, his needs grew in arithmeti c progression but corresponding pollution grew in geometric progression. With increase in agriculture produce, a need was felt to preserve the glut production in the form of processed foods giving rise to massive development of food processing industries all over the world. The rapid industrialization of agriculture and horticulture, increased the pollution load many folds especially the biodegradable waste from food industry [41].The wineries and distilleries (distill wine to make brandy) are no exception. Nevertheless, the waste is a precious source of several useful materials as such or after fermentation [1,31,46,86]. Thus, development and environment are two sides of the same coin.

From time immemorial, the biosphere is acting as a sink for all the waste products and recycles them to make good the loss so that every generation finds it the same as one before it. But, of late, this self-cleaning and equilibrium maintenance of biosphere is disastrously disturbed as the waste produced from man’s activities is continuously exceeding the capacity to purify herself. Consequently, our biosphere is becoming more and more poisonous and days are not far away when this planet will become inhabitable.

11.1 Introduction

Fermented foods are the result of the activity of a few specialized types of micro-organisms among the thousands of species known to mankind. Success of such processes is depended upon the control of environmental conditions ensuring the growth of the desired microbial species and inhibition of others. The fermentation can be broadly defined as the process in which the carbohydrate or like compounds are broken down, under anaerobic or aerobic conditions [171]. The basic role of micro-organisms is to breakdown the organic compounds to get energy for their metabolic activities. From ancient times, people all over the world have developed traditional processes for production of alcoholic beverages (wine) either from natural sugar such as in wine or by degrading the starchy materials (beer). Fruit wines referred to as ‘Soma’ in our ancient scriptures have been part of food of man and were used as medicine, might have originated accidentally (transformation of fruit juice beverages having exhilarating or stimulating properties). Wines are made principally from fruits like grape or extract of other fruits of various types (table wine, sparkling wine, dessert, aperitif or vermouth and pop wines) while the beers are prepared from grains like barley, rice and corn. The principal carbohydrate in grain is starch which can not be fermented directly. This process is brought about by starch splitting enzymes by germinating the grains followed by drying and storage until needed. Distillation of beer produces a variety of liquors (whisky, rum, gin, vodka), while that of wine produces the brandy. Besides, the improvement in the raw material selection, fermentation conditions and techniques, a lot of waste material is generated during fermentation process in the industries. Nevertheless, the food based industries are significant contributors to the economy of the many countries of the world (Fig 1). The global market value of food fermentation based industries is estimated to be around 250 million US dollars. Interestingly, more than 10% of this accounts for alcoholic beverages (Fig 2) with projected increase of US$ 27 billions in 1989 to 40 billions in 1990 [93,123,123,129].

10.1 Introduction

Edible oil production is a separate sector of the food processing industry. There are several species of plants in the world whose oil can be utilized for human consumption for edible and non-edible uses. Though around 40 oilseeds are known, only around a dozen oilseed crops have become commercially important including ten seed crops and three tree crops. These oil seed crops (mostly annual) of commercial importance are groundnut, rapeseed-mustard, sesame, soybean, sunflower, cottonseed, safflower, niger, castor and linseed. The three major tree oil crops are palm, olive and coconut [63]. Besides these, the kernels of some other tree crops i.e. apricot, almond, walnut, hazelnut, olive (fruits are used), peach, can also be utilized for oil extraction purposes for edible and non-edible uses. Besides oil of the oilseed crops, the oils of tree fruits and kernels are also becoming popular very fast for various food, pharmaceutical and cosmetic industries.

Large scale requirement and local shortages of oils for various edible and non-edible uses have prompted the identification of many new sources of oil during the last few decades. They are ricebran, corn, sal, mahua, jatropha, kokum, melia, rubber, mango kernel, kusum, simarouba, neem, karanj, crambe, moringa, tumba, jojoba and tobacco seed etc. Most of these oilseeds and their products have wide utility in the specialty oils sector and are mostly used for non-edible purposes. Soaps and detergents, paint and varnish, lubricants, pesticides and medicines, cosmetics, bio-diesel fuel industry are the major consumers of these non-traditional oilseeds. All the oil crops will gain greater attention in future as they are renewable and biodegradable in nature [63]. List of oil crops have been given in Table 1.

9.1 Introduction

Depleting natural resources, regulations on synthetic material, growing environmental awareness and economic considerations today happens to be major driving force for utilization of wastes from the agricultural crops and their residues throughout world [1]. These challenges have led to the introduction of sustainable waste management practices via optimization of processing technologies for minimization and creative conversion of the plant and the processing industries biowastes the world over [2,3,4,5]. Although world prices for sugar and petroleum products have shown spectacular variations during the last few decades, the long term outlook is very likely to be a continuous increase in the price of all fossil fuels and stagnation, at best, for the price of sugar [6]. This gloomy prospect led to the renewed interest in the wastes of the sugarcane industry during the last 50 years and has proved that the optimal use of wastes can provide not only a non-negligible support to the sugarcane industry but will also be able to redress the difficult situation sugar is presently experiencing [7]. Reliable statistics are not available to show the detailed end uses of these wastes on a world basis, but from a very rough picture of their trade, we can say that the wastes from the sugar and jaggery industry serve to be amongst the richest bioresource in this era of recycling of biowastes for renewable wealth generation [8].

8.1 Introduction

Spices are appetizers and hence, esse ntially used in the culinary preparations. They also possess antioxidant, antimicrobial and antibiotic properties. Further, they possess medicinal properties and hence, play an important role in human health.

According to International Organization for Standards (ISO), there is no clear cut division between ‘Spices’ & ‘Condiments’ and as such they have been clubbed together. The term ‘Spices’ & ‘condiments’ applies to “such natural plants or vegetable products or mixtures there of, in whole or ground form, which are used for imparting flavour, aroma and piquancy and seasoning of foods”. Spices are divided into different groups based on their plant components such as floral, fruits, berries, seeds, rhizomes, roots, leaves, kernel, aril, bark, bulbs etc.

About 70 spices are grown in different parts of the world and a major portion of these are grown in India. Hence, India is called “The home of Spices”. It is well known that spices played a significant role in ancient times, in the development of civilization – the life of the people and trade among the nations of East and West. Spices like ginger, pepper and turmeric have an intense and immediate impact on sensory perceptions and exhibit strong physiological effects as food and medicinal constituents. Some spices and herbs like cardamom, saffron and vanilla, which have less intense but more delicate sensory effects, are well known for their contribution to fragrance and usage as food flavouring agents. The history of spices and their use in food and medicine in ancient India have been reviewed earlier [1-3].

7.1 Introduction

Fisheries are emerging as one of the fastest growing food production system all-over the world. The potential for fisheries development world over and especially in India is highly promising in view of physical and biological resources available coupled with technological development. The demand for fish fishery products is ever increasing as the awareness of health benefits are being made available to public at large. The world fish production has not kept pace with demand which means less and less fish is available. Nevertheless, a large fraction of this valuable commodity is wasted due to deterioration after landing or consumer preference. An estimate by FAO [1] indicates nearly 20-25% of the total catches are wasted as postharvest loss. Better utilization of aquatic resources should therefore, aim primarily at reducing this enormous loss by improving preservation of fish and fishery products and upgrading the discarded low value fish to high value fishery products. The processing of fish into different types of products generates considerable waste. Commercially, fish is being processed into fillets, steaks, mince, canned products and a variety of ready-to-eat products. Fish processing plants contributes substantial wastes in the form of skins, bones, offal, exoskeletons from shrimps and nutrients in wash water from surimi plants.

Fish processing waste utilization is an important issue for the seafood industry both from a regulatory standpoint as well as one that has potential economic impacts. It is estimated that only 25-50% of the raw material is utilized for primary products (fillets, canned and stabilized mince production). The remaining 50-75% of the raw material is considered processing waste and is utilized for low-value products or disposed-off at sea. A large volume of solid waste is currently processed into fish meal, fish protein hydrolysates, and fertilizers. A small percentage is processed into higher valued items, such as, seafood flavourants, colourants, chitosan, enzymes, etc.

6.1 Introduction

The food industry produces large volumes of waste both solid and liquid, starting from the initial step of raw material to the final consumption of processed food. Apart from a loss of valuable biomass and nutrients, the generated waste poses increased disposal and potentially severe pollution problems. Meat and meat industry is no exception where slaughter houses, meat processors, wholesalers and rendering plant generates huge amount of waste [1, 2].

Meat and meat processing industry, is among the least profitable industries despite its immense size and large gross sales. Effective recovery and utilization of by-products and wastes is the lifeline of meat and poultry processing industry. Thus, it becomes imperative that an effort be made to reduce expenses by employing the use of new or modified processing methods and through in-plant treatment, where waste effluents and by-products could be recovered and often upgraded to useful products of higher value. Meat processing wastes have a potential for recycling raw materials or for conversion into useful products of higher value as by-product or even as raw material for other industries or for use as food or feed after biological treatment.

5.1 Introduction

Waste from the dairy processing industry is generated through production of milk products at different stages. With diversification of dairy products, by-products have also gained some importance. Utilization of dairy by- products improves economical and nutritional aspects of milk production and reduces environmental pollution originating from dairy waste. Important dairy by-products include butter milk, ghee residues and whey, the major waste arising from production of cheese, casein, paneer and chhana. Whey arises as a result of protein coagulation/precipitation in the preparation of these products. It is used for manufacture of whey powder, whey drinks and lactose (milk sugar). Whey protein concentrates can be prepared by modern technological methods like ultra-filtration and reverse osmosis. Desi buttermilk is an important domestic beverage since olden days. Ghee residue can be utilized for manufacture of chocolate burfi, samosa filling etc. Hence, utilization of dairy waste particularly whey, butter milk and ghee residues obtained during manufacturing of various main products, has not only increased the availability of nutritional milk foods but has also indicated the profitable method of by products utilization and helped in minimizing the problems of pollution. This chapter focuses on utilization of these dairy industry wastes.

4.1 Introduction

A huge amount of waste in the form of liquid and solid is produced in the fruit and vegetable processing industry which causes pollution problem if not utilized or disposed off properly. Generally solid waste is dumped in local landfills, eaten and scattered by stray animals, which has now become a major cause of environmental pollution. The waste obtained from fruit processing industry is extremely diverse due to the use of wide variety of fruits and vegetables, the broad range of processes and the multiplicity of the product [79]. The solid waste from fruits and vegetables includes peel, stone, rag, seed, core etc is of economic value and can be used for manufacturing of various by-products [21]. The extent of the waste produced from processing industries of some of the important fruits and vegetables, is given in Table 1.

In India, utilization of fruits and vegetables for processing is hardly 1.8% of the total production. There were 5166 processing units till 1^st Jan, 2009 of fruits and vegetables products throughout the country. About 90% of these units are small scale units with annual production limit of 50-250 tonnes. These units have no organized methods of waste disposal. In certain places this waste is taken away by farmers for their disposal as cattle feed or field manure.

1.1 Introduction

Due to the ever increasing world population, the demand for food would also increase. India is one of the largest food producer countries of the world (first in milk production, second largest in fruit and vegetable production and third largest in grains production). It is the seventh-largest country in the world, with a total land area of 3,287,263 square kilometres. India has varied climates of snow covered Himalayas, desserts, oceans, fertile plains and areas receiving the highest rainfall in the world. Name any food item; it can be grown in one or the other part of the country. All these make the production of various types of foods of plant (fruits, vegetables, cereals, pulses, oilseeds, spices etc) as well as animal origin (fish, meat, milk etc.) possible in the country. The annual production of cereals, fruits and vegetables is 260, 57 and 77 million tonnes respectively, besides this, the production of cow and buffalo milk is about 102.1 million tonnes and that of sugarcane and spices are 355.52 and 1.1 million tonnes respectively [15]. Table 1 shows that the production of various food items has increased many folds during the last five decades. On one hand, we feel proud as we produce one of the largest quantities of foods in the world and there has been an enormous rise in the production of various foods in India during the last five decades, on the other hand we should be very much worried being a leading country as far as the wastage of food in the world is concerned. The postharvest losses are huge and only meagre quantity (2%) of the food is processed. Sharma [41] very rightly said that when we do not agree to throw away Rs 4000/-per month out of a salary of Rs 10,000/-per month then why do we accept 40% postproduction losses of food in the country. This would require immediate necessary action to save a major portion of the food that has already been produced.

3.1 Introduction

The production of food grains in India is around 200 million tonnes and most of the grains are converted to primary products after primary processing such as threshing, dehulling, de-branning. Some of the grains are converted to secondary products such as flour or grits. The yields of primary and secondary products range between 65-80% indicating a wastage of 20-35%. These wastes lead to unclean surroundings and air pollution due to fine dust. Hence, proper waste management/utilization of food grain processing industries has become a societal need for a clean environment.

The term ‘waste’ has different meanings to different people. It can be retractions from the main process or less utilizable by-products or undesirable waste material depending on the commodity. All food-processing industries generate wastes and create problems for its management. The best way the food processing industry can treat its waste is to avoid producing it. Much of the waste now being produced or generated in some food processing plants can become a managed resource for producing economic credits. In fact, waste utilization is one of the world’s prominent industries and its activities cut across the normal divisions into which industries are placed. Similarly, there will be wastes from agriculture, animal and meat industries, textile, rubber etc. Even the local governmental activities that collect and dispose the household wastes become apparent in terms of the huge size of it.

2.1 Introduction

Each step in the food industry system e.g. food production, processing, transportation, storage, distribution and marketing, has some impact on the environment and there is much concern about environmental pollution. Due to the highly diversified nature of the food industry, various food processing, handling and packaging operations create wastes of different quality and quantity, which, if not treated, could lead to increasing disposal problems and severe pollution problems [24]. The preservation of the natural environment from industrial pollution is currently receiving much attention. In food industry, the most important problem is treatment and disposal of large quantities of waste water, a by-product of various processing operations. It is one of the largest industry groups comprising the manufacturing sector of the U.S. economy [47]. Likewise, India is the world’s second largest producer of food next to China, and has the potential of being the largest food processor. The total food production in India is likely to double in the next ten years [22]. Flour and grain; soft drinks and carbonated water; breweries; starch and miscellaneous food products; meat, poultry and fish; tea, coffee and other beverages; fruit juices; animal feed; sugar; distilleries and blending of spirits; cocoa, chocolates and sugar confectioneries; agricultural and food chemicals and industrial packaging are important sub-sectors of the food processing industry. Food processing projects involve the processing and packaging of meat products, fish and shell fish, dairy products, fruit and vegetables, grains and beverages production. It includes refinement, preservation, improvement of product, storage, handling, packaging and canning (Fig. 1). The processing may involve receiving and storing raw or partially processed plant, animal or other food materials, processing the raw materials into finished products, packaging and storing the finished products.

Microscope

A microscope can be defined as an optical instrument consisting of a lens or a combination of lenses for getting magnified images of minute objects. A simple microscope is essentially an ordinary magnifying lens held on an adjustable stand. It can give magnification up to 20 times the size of the object.

A compound microscope consists of two separate lens system, the objective and eye piece (ocular) mounted on a holder known as body tube and with adjustment for illuminating the objects. It gives much greater magnification (100 to 1500 times) when compared to a simple microscope.

Physical Methods of Food Preservation

Conditions too stressful for microbial growth can damage cells. Food environments can be manipulated to inhibit or kill microbes. Physical manipulation of foods can inhibit microbial growth, kill cells, or mechanically remove them from the food. Dehydration, refrigeration, and freezing inhibit microbial growth. Microbes can be killed by heating or ultraviolet (UV) or ionizing radiation. Non thermal energy is also lethal. Membrane filtration removes microbes from liquid foods. This chapter discusses all these physical preservation methods

Physical Dehydration Processes

Drying

When foods are being dried, hot air evaporates the water and carries it away. Both the drying temperature and the decreased water activity (a_w) affect the microbes.

During the initial period of drying, the temperature is still low and the relative humidity is high. The size and composition of the food particle determine the length of this phase. If this particle size is large and the material is dense, this phase can be long, allowing microbes to grow. During later phases of drying, the temperature is high but the relative humidity is low. This provides no opportunity for growth but is not very lethal either. The higher temperatures result in lower moisture content, and dry heat is less lethal than wet heat. If the drying lasts long enough (at least 30 min.), there are time-temperature combinations that kill microbial cells. With certain drying methods, the surface temperature may reach 100°C, while internal temperature remains lower. This kills surface microbes, but not those in the food’s interior.

Bacterial species vary greatly in the ability of their cultures to remain alive after the completion of growth. Some species such as Neisseria gonorrhoeae and Streptobacillus are poorly viable and their cultures usually die out within a few day, whether kept at 37°C at room temperature or at 4-5°C; thus, they must be sub cultivated every 2-4 days for maintenance in the laboratory. Other species are much hardier,. especially sporing species which may remain viable for many years. There are also many non - sporing species (enterobacteriaceae) whose cultures, under suitable conditions, commonly remain viable for many months and often for as much as 10-20 years.

Sterilization is defined as the process by which an article, surface or medium is freed of all living microorganisms either in the vegetative or spore state.

Disinfection means the destruction or removal of all pathogenic organisms, or organisms capable of giving rise to infection. Chemical disinfectants which can be safely applied to skin or mucous membrane and are used to prevent infection by inhibiting the growth of bacteria are called antiseptics.

Five main methods are used for sterilization. 1. Red heat (flaming) 2. Dry heat (hot air) 3. Moist heat 4. Filtration 5. Radiation.

The killing effect of dry heat is due to protein denaturation, oxidative damage and toxic effect of elevated levels of electrolytes. The lethal effect of moist heat is due to the denaturation and coagulation of protein. In the case of spore, steam condenses on it, increasing its water content with ultimate hydrolysis and breakdown of the bacterial protein.

When unwanted organism settle on objects, substances or pure culture is called contamination.

Infection

Invasion of the body of a man or an animal or a plant by disease producing organism. Infectious disease is a condition brought about by an infection of the body by an organisms which is responsible for the disease. Organism that are capable of bringing about infectious diseases are called pathogens while those organism without this capacity are said to be non pathogenic.

Commensals

Organisms on skin and mucous membrane which multiply without causing damage to the tissue.

Subclinical infection / latent infection

When organism enters the tissue and lead to immunity without the appearance of any definite clinical symptoms.

A five-kingdom classification system fails to classify viruses because they are not considered to be living. They neither reproduce independently nor utilize energy

General properties of virus

Viruses differ fundamentally from other classes of microorganism in that:

1.They are ultramicroscopic disease-producing entities.

2.They are simple in structure, basically composed of nucleic acid wrapped up in a protein coat.

3.The genome nucleic acid is either DNA or RNA , either single stranded or double stranded, but never both

4.Viruses have no metabolic activity of their own and lack enzyme systems and other constituents fundamental for independent growth and multiplication.

5.They do not posses ribosomes, nor transfer RNA and enzymes required for synthesis of nucleic acids and proteins.

6.Viruses are incapable of growth and division.

Culture methods employed depend on the purpose for which they are intended. In the laboratory the indications for culture are mainly to

1.Isolate bacteria in pure culture.

2.Demonstrate their properties

3.Obtain sufficient growth for preparation of antigens and for other tests.

4.Type isolates by methods such as bacteriophages and bacteriocin susceptibility.

5.Determine sensitivity to antibiotics

6.Estimate viable counts

7.Maintain stock solution

What are Genes? Genes are linear sequences of nucleotides of DNA (deoxyribonucleic acid). Each gene consists of a specific sequence of nucleotides and is responsible for determining a particular characteristic of cell. Nucleotides consist of nitrogen –containing compounds called bases, joined to the sugar, deoxyribose and to phosphate. The nucleotide bases are the purines, adenine and guanine and the pyrimidines, thymine and cytosine.

A number of genes are joined together to form a structure called a chromosome.

DNA consists of two strands of nucleotides twisted around each other into a double helical structure. The nucleotide bases are arranged in a specific sequence in each strand. The strand has a backbone of sugar and phosphate from which the bases protrude.

Metabolic Processes in Bacterial Cells

All living cells are continually undergoing processes of replication, breakdown, synthesis and repair. The overall term used to describe these processes is metabolism and refers to all the different reactions that must occur in order for a cell to grow and reproduce. The pathways of metabolism are remarkably similar in all living cells. The differences that do occur usually reflect the availability of nutrients or the need for a cell to provide for a specific function. This may be secretion, storage, structural support, energy for movement, or reproduction. Our knowledge of many of the metabolic processes that occur in human cells has been derived from research on the major pathways that also occur in microbial cells.

Catabolism is the process of breakdown of complex molecules, usually with the release of energy. Anabolism refers to the synthesis of new or replacement molecules. This is an energy-requiring process. A metabolic pathway is a series of reactions in the process of metabolism.

The energy from the sun that is trapped and used to produce glucose is released when a molecule of glucose is broken down during metabolism. This complex process is called oxidation, or respiration, and consists of a number of interrelated biochemical pathways, including those of glycolysis, fermentation and aerobic respiration. Reactions that occur in the presence of oxygen are termed aerobic; those that occur in the absence of oxygen are anaerobic. Many of these reactions require the involvement of various cofactors as well as enzymes, and result in the production of energy which is captured by the synthesis of a small molecule called adenosine triphosphate (AT). ATP is termed an ‘energy-rich storage molecule’ because breakdown of ATP releases energy for use in other reactions in the cell.

Growth of a microorganism implies an increase in amount of protoplasm, formation of new structures and eventually formation of new cells. Balanced growth means cell components increase in proportion to each other and unbalanced growth means cell components increase in a non constant relationship to each other

Microbial growth and growth curve

Phases of growth

When bacteria are grown in the laboratory in liquid medium, the medium becomes cloudy or turbid. It is possible to measure the increase in numbers of bacteria at various time intervals and plot the values on a graph representing a growth curve.

Lag Phase: When cells are first inoculated into fresh medium containing all the nutrients they require, they take a short time to adapt before they start to divide. This is termed the lag phase.

Yeasts

Yeasts are non filamentous, unicellular fungi that are typically spherical or oval. Like molds, yeasts are widely distributed in nature; they are frequently found as a white powdery coating on fruits and leaves.

Cultural characteristics of bacteria deal with the appearance of the growth in various liquid and on solid media. The growth characteristics of most of the bacteria are typical of the group or species and help in their identification. The terminology employed to describe various features of bacterial growth are mentioned below.

Bacteria are morphologically different. This characteristic is helpful in the identification of bacteria. Routine study of bacterial morphology should include examination of stained preparations. Motility should be examined by hanging drop preparation. According to the requirement, certain cell structures may be stained. Stained preparations should be made preferably from fresh agar slant cultures. Smears of Streptococcus should be made from a liquid culture. Morphology of bacteria may be described under the following terms:

1.Shape: Spherical, coccobacillary, short or long rods, filamentous, comma- shaped, curved or spiral forms.

2.Size: Spherical are measured in diameter and rod-shaped in length and breadth. Measurement is expressed in microns (µ).

3.Sides: Straight, concave, bulging, parallel or irregular.

4.Ends: Round, pointed, truncate or concave.

5.Axis: Straight or curved.

6.Arrangement: Singly, in twos, in groups of four or eight, in grape-like bunches, in long chains, or scattered irregularly, may be in bundles, angular arrangements or in Chinese letters.

7.Pleomorphism: Bacteria may differ from their typical shape. Some of the older cultures may depart greatly from their typical forms, and may show spindles, clubs, and filaments, swollen and branching forms. Variation may be both in shape and size.

8.Capsule: May or may not be present. When present, size should be noted. This requires special staining.

Size shape and Appearance of Bacterial cells

Bacteria vary significantly in their morphology, that is in their appearance. They range in size from 0.2 μm to1 μm in diameter and 1 μm to 10 μm in length. There are three basic shapes of cells :

1. Spherical

2. Rod-shaped

3. Spiral.

Improvements in microscopes enabled scientists to study the ‘invisible’ organisms – that is, those too small to be seen with the naked eye. They were able to show that certain of these microscopic creatures are responsible for the infectious diseases of higher organisms. Most of them are harmless, some are essential for life and some are used in the manufacture of products that are of benefit to humans.

One of the major discoveries that gave birth to the field of microbiology was the development of instruments that could magnify, so that objects too small to be seen with the naked eye could be visualized. Robert Hooke in 1665, using an instrument with two sets of lenses (a crude compound microscope), was the first person to describe cells as life’s smallest structural units. In the early 1670s Anton van Leeuwenhoek used a simple magnifying lens to observe microbes he called ‘animalcules’ in rainwater, and was possibly the first person to observe microorganisms. The development of electron microscopes in the 1930s enabled magnifications of a further hundred times greater to be achieved.

A microscope can be defined as an optical instrument consisting of a lens or a combination of lenses for getting magnified images of minute objects. A simple microscope is essentially an ordinary magnifying lens held on an adjustable stand. It can give magnification up to 20 times the size of the object.

Microorganisms (or microbes) are organisms too small to be seen with the naked eye. The science of microbiology is the study of microorganisms, their properties, classification, growth requirements, method of reproduction and distribution in nature. These organisms range in size from tiny viruses to larger bacteria, protozoa, algae, fungi and some of the microscopic worms (helminthes). They are present everywhere in our environment, in our homes, on our bodies, on the things we touch and on the food we eat. They are important for human survival on Earth, playing an essential role in many processes that maintain life. In nature, microorganisms carry out a number of important functions.

1.They are responsible for the decomposition of organic matter.

2.Recycling of nutrients that help to maintain the balance of chemicals in the soil.

3.Special nitrogen-fixing bacteria live symbiotically with certain plants, absorbing nitrogen from the air and converting it into compounds which can be used by the plant for growth.

4.Some algae are capable of photosynthesis, using energy from the sun to convert carbon dioxide in air into carbohydrate.

5.Marine microorganisms form the basis of the food chain in lakes, rivers and oceans.

6.Certain microorganisms are used in the manufacture of food.

7.Pharmaceuticals and drugs.

8.Industrial processes.

9.A valuable tool for scientific research.

10.Use in laboratory experiments to understanding metabolic pathways and in the discovery of the genetic code.

Ex.No.1. MICROBIAL SPOILAGE OF FRUITS

Fruits are living structures that continue to perform metabolic reactions and sustain physiological processes for a considerable length of time after harvest. The post-harvest infection of fruits by microorganisms may cause serious losses of fruits both in terms of quantity and quality. Initial infection which may be the direct result of mechanical or insect damage is followed by invasion of fruit tissues by secondary infection by common saprophytic organisms. . Many bacteria and fungi, for instance, are involved in decay after harvest. Typical fungi include Alternaria, Botrytis, Colletotrichum, Fusarium, Monilia, Penicillium, and Rhizopus. These fungi are generally weak pathogens, in that they usually infest only weak or damaged fruit. Molds are the most predominant spoilage organisms in fruits. Fungal rots in fruits like apple show brown or cream coloured areas.

Bacterial soft rot caused by Erwinia carotovora is wide spread in fruits that are not very acid. Fruits like straw berries, melons are in direct contact with moist soil and become infected from that source.

GENETIC ENGINEERING

Genetic engineering is a means of improving the food supply even before harvest or slaughter by improving yields, increasing disease resistance, and enhancing the nutritional qualities of various foods. Broadly speaking, genetic engineering refers to any deliberate alteration of an organism’s DNA. Genetic engineering has been practiced for thousands of years, ever since humans began selectively breeding plants and animals to create more nutritious, better tasting foods. In the past two decades, genetic engineering has become increasingly powerful as scientific advances have enabled the direct alteration of genetic material. Genetic engineering is alternately called as ‘ recombinant DNA technology’ or ‘gene cloning’. Genes have been cut and pasted from one species to another, yielding, for example, disease- resistant squash and rice, frost-resistant potatoes and strawberries, and tomatoes that ripen-and therefore spoil-more slowly.

Genetically modified organism (GMO) is a microbe or more complex plant or animal in which DNA has been altered for a particular purpose such as manufacturing proteins, making improvement to the organism, research into the nature of genes and biological process, correcting genetic defects.

Fungi cause diseases in plants and animals and in such diseases, the fungi actively grow and invade the body of their hosts. There is another means by which fungi can cause harm is growing on stored food material that we consume and produce toxic metabolites referred to as mycotoxins (means fungus poisons). Food is particularly susceptible to fungal infections at almost every stage of storage or production. Mycotoxin is toxic substance produced by a fungus. The term is restricted to toxins produced by fungi growing in human foods or animal feeds. The growth of the fungi in food grains leading to physical spoilage of grains and toxin production is a serious problem in developing countries. Their occurrence in food and feed has both economic and health implications, as the toxic effects in human beings, animals and other living systems were well established. The effects of poisoning by mycotoxin are referred to as mycotoxicoses.

Food poisoning is an acute illness resulting from the ingestion of injurious agents such as chemical, heavy metals, parasites, microbial toxin, wild species of mushroom in food. Food poisoning is commonly caused by certain bacteria or their toxins, which are the poisonous proteins that these bacteria produce. Food borne pathogens are potential global problem, more than 90 per cent of the cases of food poisoning are caused by bacteria, Staphylococcus aureus, Salmonella spp, Clostridium perfringens, Campylobacter jejuni, Listeria monocytogenes, Vibrio parahaemolyticus, Shigella dysenteriae, Bacillus cereus and enteropathogenic E. coli. These bacteria are commonly found in many raw foods. Generally a large number of food poisoning bacteria must be present to cause illness. In most of these food poisonings, the food serves as a vehicle of transmission. The role of food here is significant, since the product not only may permit the survival of the pathogens, but also may provide a suitable medium for the rapid multiplication of microbes and production of toxin. A more serious aspect of microbial contamination is the possibility of serious health hazards due to potential pathogenic organisms gaining entry into foods due to low standards of hygiene and sanitation.

Food poisoning may be due to food intoxication or food infection. Food intoxication and food infection differ in many characteristics (Table 17.1). Food intoxication refers to food borne illness caused by the ingestion of a microbial toxin preformed in the ingested food (Botulism). The most serious food poisoning caused by toxins is botulism, an often fatal disease that results from eating improperly canned foods containing the bacteria Clostridium botulinum. Classically, food intoxication is caused by the growth of Clostridium botulinum, Staphylococcus aureus, Bacillus cereus in food. Clostridium botulinum produces a neurotoxin, while Staphylococcus aureus and Bacillus cereus cultures produce enterotoxins in food.

16.1. CANNED FOODS-PRESERVATION

Canning is a method of preserving food from spoilage by storing it in containers that are hermetically sealed and then sterilized by heat. The process was invented after prolonged research by Nicolas Appert of France in 1809, in response to a call by his government for a means of preserving food for army and navy use. Appert’s method consisted of tightly sealing food inside a bottle or jar, heating it to a certain temperature, and maintaining the heat for a certain period, after which the container was kept sealed until use. It was 50 years before Louis Pasteur was able to explain why the food so treated did not spoil: the heat killed the microorganisms in the food, and the sealing kept other microorganisms from entering the jar. Samuel C. Prescott and William Underwood of the United States set canning on a scientific basis by describing specific time-temperature heating requirements for sterilizing canned foods.

Most vegetables, fruits, meat and dairy products, and processed foods are stored in tin cans, but soft drinks and many other beverages are now commonly stored in aluminum cans, which are lighter and do not rust. Aluminum cans are made by impact extrusion; the body of the can is punched out in one piece from a single aluminum sheet by a stamping die. This seamless piece, which has a rounded bottom, is then capped with a second piece as its lid. The tabs used in pop- top cans are also made of aluminum. Bimetal cans are made of aluminum bodies and steel lids.

Canneries are usually located close to the growing areas of the product to be packed, since it is desirable to can foods as quickly as possible after harvesting. The canning process itself consists of several stages: cleaning and further preparing the raw food material; blanching it; filling the containers, usually under a vacuum; closing and sealing the containers; sterilizing the canned products; and labeling and warehousing the finished goods. Cleaning usually involves passing the raw food through tanks of water or under high- pressure water sprays, after which vegetable or other products are cut, peeled, cored, sliced, graded, soaked, pureed, and so on. Almost all vegetables and some fruits require blanching by immersion in hot water or steam; this process softens the vegetable tissues and makes them pliable enough to be packed tightly, while also serving to inactivate enzymes that can cause undesirable changes in the food before canning. Blanching also serves as an additional or final cleansing operation.

15.1 CONTAMINATION

Milk is sterile at secretion in the udder, but contaminated by bacteria when it leaves the udder of a healthy cow. Milk is subject to contamination from the animal and adjacent areas. Bacteria found in manure, soil and water may enter milk from these sources. Certain diseases may be transmitted through milk, from a cow. It is essential that cows producing milk should be free from any contagious or infectious disease. Bovine tuberculosis comes from consumption of milk of tuberculous cows. Tuberculosis, brucellosis, mastitis and actinomycosis are the human disease transmitted through milk. The disease producing bacteria may find their way into milk and cause infectious diseases in children and adults.

COMMON BACTERIA IN MILK: The common bacteria found in milk are: Rickettsia, Coxiella burnetii, lactic acid bacteria, Lactobacillus bulgaricus, Streptococcus thermophilus, aerobic rods, Bacillus subtilis, Bacillus cereus, anaerobic bacteria, Clostridium butyricum .

Sources of Microbial contamination: Milk contains relatively few bacteria when it leaves the udder of a healthy cow. Milk is subject to contamination from the animal udder, skin and adjacent areas barn yard, milk utensils, milkers. Bacteria found in manure, soil and water may enter milk from these sources.

14.1. EGGS

India is the third largest producer of eggs. Fresh eggs are gathered on automatic collection belts at the farm and stored in a cooler at about 7°C. The eggs are then delivered to a central processing plant, where they are washed, sanitized, and graded. Grading involves the sorting of eggs into size and quality categories using automated machines. Flash candling (passing the eggs over a strong light source) detects any abnormalities such as cracked eggs and eggs containing bloodspots or other defects. Higher-grade eggs have a thick, upstanding white, an oval yolk, and a clean, smooth, unbroken shell.

14.1.1. Eggs Contamination

More than 90 percent of all eggs are free of contamination at the time they are laid; contamination with Salmonella bacteria and with certain spoilage organisms occurs essentially afterward. They become contaminated by faecal matter from the hen, by the lining of nest, by handling, by wash water and packing materials. The total number of microorganisms per shell of a hen’s egg was found to range from 100 to 10,000,000 with a mean of about 100,000. Proper washing and sanitizing of eggs eliminates most Salmonella and spoilage organisms deposited on the shell. The organism Salmonella enteritidis, a common cause of gastroenteritis (a form of food poisoning), has been found to be transferred through the hen ovary in fewer than 1 percent of all eggs produced. Ovarian- transferred S. enteritidis can be controlled by thorough cooking of eggs (i.e., until there are no runny whites or yolk).

13.1. CONTAMINATION

MICROFLORA: The flora of living fish depends upon the microbial contents of the waters in which they live. The slime in the outer surface of the fish contain bacteria of the genera: Pseudomonas, Alcaligenes, Micrococcus, Flavobacterium, Corynebacetrium, Bacillus, Sarcina, Serratia and Vibrio. The same species of bacteria are found in shrimps, crabs, lobsters and similar sea foods. Oysters and Shell fish that pass large amount of water through their bodies, pick-up soil and water microorganisms in this way including human pathogens. Common spoilage microorganisms of fish include species of Pseudomonas, Moraxella, and Acinetobacter, found mainly in marine fish, and Bacillus and Micrococcus, found in freshwater fish. Fish may also contain pathogenic (disease-causing) microorganisms such as Salmonella and Escherichia coli. Pathogenic contamination is of special concern with mollusks because they are often eaten raw and as whole animals.

SOURCES: Boats, boxes, bins, fish houses and fishermen are the sources of contamination of these bacteria. The bacterial population ranges from few hundred to few million per square centimeter. Because of their soft tissues and aquatic environment, fish are extremely susceptible to microbial contamination. At the time of harvest, fish carry a high microbial load on the surface of their skin, in their intestinal tract, and in their gills. The type and number of microorganisms that live in fish vary according to the season, the species, and the natural habitat. Additional contamination may occur during the harvesting, handling, or processing of the fish. Harvested fish must be immediately stored in a low-temperature environment such as ice or refrigerated seawater. This chilling process slows the growth of microorganisms that live in fish and inhibits the activity of enzymes. Because fish have a lower body temperature, softer texture, and less connective tissue than land animals, they are much more susceptible to microbial contamination and structural degradation. If immediate chilling is not possible, then the fish must generally be sold and eaten on the day of the harvest.

CONTAMINATION

The healthy inner flesh of meat contains few or no microorganisms, although they have been found in lymph nodes, bone marrow and intestine. Staphylococcus, Streptococcus, Clostridium and Salmonella have been isolated from lymph nodes of red meat animals. During slaughtering the lymph nodes are removed from edible parts. The important contamination, however comes from external sources during bleeding, handling and processing. During bleeding, skinning and cutting the main sources of microorganisms are from the exterior of the animal- hide, hoof and hair and the intestinal tract. The exterior of the animal harbours large number and many kinds of microorganisms from soil, water, feed and manure as well as its natural surface flora.

Knives, cloths, air and hands and clothing of workers can serve as intermediate sources of contamination. During handling and processing the contamination can come from containers, air, other contaminated meat, equipments and personnel.

Molds that grow on the surface of the meat include the species of Cladosporium, Sporotrichum, Geotrichum, Mucor, Monilia, Penicillium and Alternaria. The important bacteria found in meat are Staphylococcus, Sarcina, Streptococcus, Clostridium, Leuconostoc, Lactobacillus, Proteus, Flavobacterium, Bacillus, Streptomyces, Escherichia and Salmonella.

11.1. FRUITS-Maturation, Ripening and Storage

Fruits are natural foods containing substantial quantities of essential nutrients and the best sources of minerals like sodium, potassium and magnesium, vitamins (antioxidants), such as vitamin A, C and enzymes. They are rich in fructose and water. Fruits are living biological entities that perform a number of metabolic functions. Two functions of particular importance in fruit processing are respiration (the breaking down of carbohydrates, giving off carbon dioxide and heat) and transpiration (the giving off of moisture). Senescence is the period when chemical synthesizing pathways give way to degradative processes, leading to aging and death of tissue. Fruit ripening is thus the result of many complex changes, some interactive but many independent of one another. Once the fruit is harvested, respiration and transpiration continue, but only for as long as the fruit can draw on its own food reserves and moisture. It is this limited ability to continue vital metabolic functions that defines fruit as perishable.

10.1 CEREALS AND CEREAL PRODUCTS

CONTAMINATION: The sources of contamination in cereals and cereal products are soil, insects, air, etc. Most of the microorganisms are removed with the outer portions of the grain during milling. The bleaching agents used during milling also reduce numbers of microorganisms. The bacteria in wheat flour include Bacillus, Micrococcus, Flavobacterium. Mold spores are chiefly of Aspergillus spp and Penicillium spp and in addition Alternaria, Cladosporium and other genera are found. The numbers of microbes in cereals and cereal products vary widely from few hundred per gram to million. Corn meal contains several hundred to several thousand bacteria and mold per gram.

Microbial contamination sources: Foods may be contaminated by microorganisms at any time during harvest, storage, processing, distribution, handling, or preparation. The primary sources of microbial contamination are soil, air, animal feed, animal hides and intestines, plant surfaces, sewage, and food processing machinery or utensils. Since most foods either carry or eventually acquire bacteria, molds, or yeasts, microorganisms are the major causes of food spoilage. The increased load of microorganisms leads to rapid spoilage.

Organisms: Bacteria and fungi (yeasts and molds) are the principal types of microorganisms that cause food spoilage and food- borne illnesses. The typical microorganisms that cause food spoilage are bacteria (e.g., Pseudomonas), yeasts (e.g., Candida), and molds (e.g., Rhizopus). The growth of microorganisms in the food will increase the load of microorganisms, and the heavier load will add to the difficulty of preventing spoilage and may influence the kind of spoilage to be anticipated.

Food spoilage may be defined as any change that renders food unfit for human consumption. These changes may be caused by various factors, including contamination by microorganisms, infestation by insects, or degradation by endogenous enzymes (those present naturally in the food). In addition, physical and chemical changes, such as the tearing of plant or animal tissues or the oxidation of certain constituents of food, may promote food spoilage. Foods obtained from plant or animal sources begin to spoil soon after harvest or slaughter. The enzymes contained in the cells of plant and animal tissues may be released as a result of any mechanical damage inflicted during postharvest handling. These enzymes begin to break down the cellular material. The chemical reactions catalyzed by the enzymes result in the degradation of food quality, such as the development of off- flavours, the deterioration of texture, and the loss of nutrients. The enzymatic changes in foods are desirable to some extent as in the case of ripening of fruits, but continued enzymatic activity beyond an optimum point becomes food deterioration due to rotting. The native enzymes may be inactivated by heat, radiation or by the use of specific chemicals.

Several attempts have been made to detect the biopotentials of microorganisms with reference to their ability to produce various enzymes with a view to use them in industrial processes and bioremediation applications. Enzymes are increasingly used as a new route to synthesize food ingredients such as flavours, emulsifiers, sweeteners, food additives, nutrients. With the advent of genetic engineering, a wide range of enzymes has become available on a large scale and this has increased the scope of enzyme technology.

MICROBIAL ENZYMES: Enzymes are proteinaceous complex organic catalysts of biological origin and vital constituents of cells. Microbes produce a variety of enzymes, intracellular and extracellular enzymes. Most of the microbial enzymes produced for commercial usage are extra cellular enzymes. Extracellular enzymes are secreted outside the cell and hydrolyze polymeric substances. Amylases and proteases are enzymes of economic importance. At present over 60 enzymes are in commercial use, of which three-quarters are hydrolytic enzymes. Commercial production of microbial enzymes utilizes a variety of fungi, yeasts and bacteria. The composition of the medium, genetic stability of the microbial strain and physical and chemical factors of fermentation influence the production of a particular enzyme.

Enzymes catalyze a variety of reactions during processing and preservation of food products and form a large group of processing aids. Food industry utilizes enzymes in the production of bakery items, dairy products, fruits and vegetables juices and products, tenderization of meat, modification of oils and fats, flavour production and preservation of food products. Enzymes have also found use in the manufacture of ingredients like glucose, high fructose syrup, citric acid, colour and flavour constituents.

Mushrooms are most ancient, best known and greatly admired fleshy macrofungi. Mushrooms are delicacies, much sought after and greatly valued foods. Wild mushrooms are mostly found in forests, tree trunks, pastures, lawns and road side during winter season and appear at surprising speed. Mushroom hunting or gathering is a popular hobby in Western countries. The wild mushrooms may be edible or unpalatable or poisonous. Poisoning by wild mushrooms is common and may be fatal or produce merely mild gastrointestinal disturbance or slight allergic reaction. The term toad stool is popularly reserved for inedible or poisonous mushrooms, but this classification has no scientific basis. This alarming term keeps many people away from these foods. It is important that every mushroom intended for eating be accurately identified. Mushrooms vary in colour, size, shape, growth habit, yielding ability and other characteristics.

STRUCTURE: Mushrooms are the fleshy fungi which constitute a major group of lower plant kingdom. Mushroom is the conspicuous umbrella-shaped fruiting body (sporophore) of certain fungi of the order Agaricales in the class Basidiomycetes but also of some other groups. Popularly, the term mushroom is used to identify the edible sporophores. The edible reproductive part consists of a stem and a cap. Gills found on the underside of the cap, are arranged like spokes in a wheel. The gills bear multiple spores which start new fungi. The sporophore emerges from an extensive underground network of fine thread like white growth known as mycelium. The mushroom, fruit body produced basidiospores at the tip of club like structures, called basidia, which are arranged along the gills of the mushroom. Beneath the mushroom, in the soil, is the mold colony itself, consisting of a mat of intercoiled hyphae, sometimes several feet in diameter. The mushrooms first appear as white tiny ball consisting of short stem (stipe) and a cap (pileus) which begins to open up like an umbrella. The delicate membrane or Veil (velum) enveloping the cap tears off, if allowed to develop fully, and lamellae (gills) radiating from the stalk into the cap become visible. These gills become darkened as the basidiospores (seeds) develop into millions and fall in the ground for starting their life cycle once again for second generation of mushrooms.

SINGLE CELL PROTEIN (SCP) AND PROTEIN DEFICIENCY

Protein is an essential component of diet. The greatest single problem in the world today is global food protein shortage. Having adequate quantity of food is only one side of the picture, but the most important aspect is the supply of balanced and nutritious food. All efforts are being made to increase the food production through modern methods of farming. But very little attention is being paid towards protein requirements and production. Approximately half of world population suffers from the protein deficiency disease called ‘Kwashiorkor’ and children with poor protein are victims of this disease.

Usually, cereals have low protein values while protein rich pulses are not available in desired quantities due to poor yields and high costs. The good quality protein available in fish, meat, poultry, and eggs is not available due to poor economic condition as well as varied dietary habits. With the current system of production, agriculture cannot be relied upon to feed an ever increasing world population. Hence there is an urgent need to find other protein sources. The best potential is seen in microbial protein or single cell protein (SCP), a new source of protein independent of agriculture.

DEFINITION: The dried cells of microorganisms such as bacteria, fungi, yeasts, algae that are grown in large scale culture systems as proteins for human or animal consumption are collectively known as "single cell proteins".

Milk is nutritious and essential food for human beings and also serve as good medium for microbial growth and contamination. Milk is a single, most nearly complete, natural food. Primarily it is meant for nourishing the newborns but man has exploited it for human consumption since long. Today milk has become indispensable integral component of our diet. About half the milk produced is consumed as fresh milk, the rest going into a variety of products including evaporated and condensed milk, dried milk powder, butter, cheese, malted milk, ice cream, yoghurt, lactose and casein. Milk is very important from a nutritional standpoint since it contained all the essential food constituents (carbohydrate-lactose, protein-casein, fat-butter, minerals- calcium, potassium and vitamins- A, B, C, D, E, and K) required in human diet in about the proper proportions. India is the second largest producer of milk in the world. India has exhibited unprecedented rate of growth in dairy development in last 30 years mainly due to sustained efforts of dairy technologists in Operation flood Programme introduced by the National Dairy Development Board. Dairy microbiology deals with aspects like shelf life and spoilage microbes, public health significance and food borne pathogens, and production of fermented dairy products.

Fermentation plays a major role in our diet and give the basic foods like bread, yoghurt, wine and cereal and legume based traditional fermented foods. The development of fermented food products can be considered as one of the greatest achievements of human civilization and goes back thousands of years. It arose from the necessity to conserve foods, to make them more digestible and also more enjoyable. During the centuries, man learned by trial and error to conduct the fermentation processes by changing physical and chemical parameters in the basic food ingredients. It took much longer, however, to discover the cause of fermentation processes: only towards the end of the 19th century it was demonstrated, that baker’s yeast is the cause of alcoholic fermentation. Through the development of the technique of "pure microbial culture", the basis for a controlled use of microbes in food industry was established.

The unique feature of fermented foods is the vital role of microorganisms that bring about essential bio-trasformations of the substrates during fermentation contributing number of desirable properties such as improved product shelf life, enriched diet with improved flavor and texture, increased safety, enriched nutritional supplement and probiotic functions. Fermentation is a chemical reaction carried out by many types of microorganisms to obtain energy. Fermentation is a process for production of a product by means of mass culture of microorganisms. In fermentation, microorganisms breakdown complex organic compounds into simpler substances. Although chemical changes and microbial growth usually mean food spoilage, in some cases fermentation is desirable and microorganisms are actually added to foods. For example, in the production of beer, wine, and other alcoholic beverages, yeasts convert sugar into ethyl alcohol and carbon dioxide. In the making of yogurt and cheese, lactic acid bacteria convert lactose, a sugar found in milk, to lactic acid. Alcohol, acids, and other compounds produced in fermentation act as preservatives, inhibiting further microbial growth. In addition to its use with alcoholic beverages, cheese, and yoghurt, fermentation is used to produce yeast bread, soy sauce, cucumber pickles, sauerkraut, and other traditional fermented food products. The variation in agroclimatic conditions prevailing in India and diverse form of dietary culture of various ethnical groups produced traditional fermented foods such as idli, dosa (rice-legume based), vada, papad, wari, balle (legume based), bhatura, jelabi, nan (wheat based), paneer, shrikhand (milk based).