eChapters

Abstract

Drying is a widely used method of food preservation. It leads to some structural changes in the dried material resulting in poor quality and rehydration. Freeze drying, though a costly process, reduces water activity without exposing the food material to high temperatures, eventually retains the original quality to a great deal. Moisture in the foods is frozen to ice which is sublimated under low pressure. Low pressure helps to vaporise the ice without transforming it to liquid, hence leaving the food structure porous in nature. The food is claimed to preserve the nutritional, sensory and re-constitutional qualities.

1.1 INTRODUCTION

Most food materials are composed of a very high percentage of water, which can be as high as 95%, and this makes them susceptible to microbial activity. Microbial activity spoils the products, leaving them useless for human consumption. It not only changes their taste and color but it may also develop toxins, thus making them unsafe. There are various methods for preserving food but in order to make them shelf stable, removing water from foods helps keep them from spoiling for a longer period of time.

Abstract

Drying is one of the most important industrial operations for preservation of food material. Due to the major limitations posed by convective drying methods, there is always a need for novel drying techniques which are technically, economically and environmentally sustainable. Based on the principle of moisture diffusion due to vapor pressure gradient, atmospheric freeze drying (AFD) offers a promising alternative to conventional drying systems. A cold gas with low water vapor pressure is used as drying medium to sublimate moisture directly from the frozen material at atmospheric pressure conditions. As a result the product gets dried at much lower temperature unlike convective drying. Thus, products dried with AFD retain better nutrition, texture and color and the process is also considerably cost effective. Major limitation of the AFD process is longer drying time, which can however be accelerated by using heat pump drying or new ultrasound technology. This chapter focuses on mechanism, benefits, limitations and comparative study of AFD with other drying methods such as hot air drying and vacuum freeze drying. It provides an insight regarding effect of AFD on properties of food material based on various studies reported in literature.

Abstract

Multiflash drying (MFD) process is based on the application of multiple cycles of heatingvacuum pulse to a solid food. Heat can be provided by convection (from hot air), conduction (by contact with a hot surface), microwaves, or by a combination of these methods. Due to the moderate temperatures applied to the drying food, and the sudden decompression step (vacuum pulse), MFD processes allow obtaining crispyanddried foods with very good nutritional and sensory properties. Vacuum pulses cause food texturization, which depends on the pressure drop rate during decompression. In fact, the dried products are similar to freezedried foods, but with more open structures, which result in higher crispness. The dehydration can be performed in relatively short processing times, when compared with traditional drying processes (e.g. solar drying, airdrying, vacuum drying and freezedrying). The short process time indicates clearly that this class of drying process presents a huge potential to the production of driedandcrisp foods at industrial scale.

Abstract

Airflow drying persists as the main dehydration operation. Indeed, the high expense of freeze-drying in term of equipment cost and energy consumption considerably restricts its use and confines its applications to high added value products (pharmaceutical products, cosmetics, etc.). However, airflow drying undergoes fundamental problems such as low operation performance, poor product quality and short reliability of the equipment. The time of drying is long; particularly at the end of the operation, which implies crucial energy consumption. The poor quality of the end product is related to thermal degradation and in particular to the compactness of texture as a result of the phenomena of shrinkage and case hardening. Another main problem common to all drying operations, including freeze-drying, is the safety of the end products. Swell-drying is defined as an operation that combines optimized hot air drying with instant controlled pressure controlled texturing. The improvement of texture, the preservation of sensory and nutritional quality, the possibility of manufacturing expanded granule powders and the reduction of drying time and energy consumption allow considering swell-drying as the most relevant drying process.

Abstract

This chapter presents the principle of fluidisation and its use in drying of food materials. Being a convective drying process, capacity and kinetics are limited by process conditions and material properties. The influences are discussed as well as presenting the main equations that describe drying in fluidised beds. The main focus lies on hot gas drying, additionally superheated steam drying as well as atmospheric fluidised bed freeze drying and microwave-assisted fluidised bed drying are presented and discussed.

Abstract

Increasing global demand for ‘fresh-like’ processed food products has forced food industries to investigate into various minimal processing techniques. Food processing in general has been associated with thermal processing, alone or in various combination with chemical and mechanical preservation and processing methods. However, thermal processing methods are energy intensive in nature and tend to reduce product quality and freshness at the cost of shelf-life gain. Advance technique such as microwave, radio-frequency and freeze drying do maintain the product quality but their implementation at industrial scale involves high operational and maintenance cost. An ideal processing method therefore would be one that can process food products without losing its quality, is energy efficient and is easily scalable. In this chapter, we discuss about ‘Electrohydrodynamic (EHD) Drying’, which is can be classified as a minimal processing technique. The heat and mass transfer principles involved in EHD drying have been extensively discussed and so has been the key consideration for designing an EHD drying system.

Abstract

Pulse combustors provide an advantageous superposition of unsteady gas flow and high intensity sound waves. Such a combination does not only accelerate drying rates because of increased heat and mass transfer but also allows processing of liquids, pastes and agglomerated solids in a dispersed state due to aerodynamic impact from the high intensity sound wave. Over last decades, applications of pulse combustion in drying have been exploited continuously and different pulse combustion dryers have been designed and fabricated. In pilot tests and technical reports on these dryers, short drying time, high energy efficiency and product quality are generally reported, which cause that pulse combustion drying is regarded as a technology of the future in convective drying.

This chapter attempt to introduce basic knowledge and state-of the art about this emerging technology and summarizes some recent studies in pulse combustion drying and equipment design. Following a concise description of pulse combustion and pulse combustor, the basic types of pulse-combustion dryers are presented, including spray dryers, fluidized bed dryers, impinging dryers, and dryers of special design. The existing commercial applications and pilot test projects are described and potential applications are identified.

Abstract

Foam Mat Drying (FMD) is an economical alternative to drum, spray and freeze-drying for the production of food powders. The raw material is converted into stable foam by adding foaming agent through beating or whipping in presence or not of foam stabilizers, and dehydrated by different classical airflow and thermal means. A high-quality food powder attributes can be obtained by the proper selection of foaming method, foaming agents, foam stabilizers, time taken for foaming, suitable drying method and temperature. FMD can be used for large production of food powders because of its suitability for all types of food materials, rapid drying at lower temperature, retention of nutritive value and bioactive compounds, good reconstitution characteristics and flowability and cost-effective for producing powders.

In this chapter, basics of foam and its structure, mechanisms of foaming, types of foaming agents and stabilizers for the production of stable foam have been discussed. The influence of foaming agents, foaming properties, thickness of foam and drying temperature on the drying characteristics of mat are also studied. This chapter analyzes the application of foam drying process for different food materials, the microstructure and whole quality attributes of obtained powder, and the energy consumption and costs of FMD as well.

Abstract

Application of ultrasound is one of the most promising uses of novel technologies in food processing. Use of ultrasound at various stages of drying has resulted in significant decrease in drying time and improvement in quality characteristics of dried products. The chapter discusses the principle behind use of ultrasound, general application in food industry with detailed description of various drying processes and equipments assisted by ultrasound.

Abstract

Cocoa and coffee are highly sought after commodity crops in the market owing to the distinct flavor and aroma characteristics. Cocoa beans are mostly used in the manufacturing of chocolates and various types of confectioneries while coffee is mainly consumed in the form of beverages. Both cocoa and coffee need to be dried and roasted in order to produce the flavor precursors which further develop into the desired flavor and aroma in the finished products. This chapter aims to provide an overview of cocoa and coffee processing with particular emphasis on drying and roasting aspects and its impact on product quality.

Abstract

Mushrooms are the fruiting bodies of fungi, a group of organism that is different from fruits and vegetables. They are a rich source of good quality protein having more essential amino acids and vitamins with low calories. There are about six commonly known edible mushrooms throughout the world with button mushroom (Agaricus bisporous) being the most familiar and commercially important variety. Mushroom is a highly perishable product with a shelf life limiting to a few days. Soon after harvest, it starts to undergo physiological disorders like shriveling, wilting, liquefaction, browning, textural as well as weight losses and flavour changes. The main responsible factors for the quality deterioration after harvest are respiration rate, browning, bacterial spoilage of mushrooms, temperature and relative humidity. Because of its limited shelf life under ambient conditions of temperature and humidity, the preservation of mushrooms is a matter of concern. Various techniques have been involved in the extension of shelf life of mushrooms including chemical treatments, cooling, modified and controlled atmospheric storage, radiation, drying etc. Drying is one of the most accepted and effective methods for the long term storage of mushrooms. Mushrooms preserved by drying have a pleasant flavour and are used as an important ingredient in several food formulations including salads, instant soups, meats and rice dishes. Various drying processes like sun drying, hot air drying, freeze drying, vacuum drying etc. can be used for the long term storage of mushrooms. As mushrooms are sensitive to temperature, determining the right drying method is the key for the successful and effective operation of the system. The different operating conditions involved in various methods of drying affect product quality considerably. The effect of drying methods on the process and the quality of the dried mushroom is explained in detail in this chapter.

Abstract

Vitamin C is one of the most important phytochemicals and can be found in almost all fruits and vegetables. Since it covers almost all eventualities, being water solute and prone to leaching from cells, thermally labile (one of the most labile vitamins), pH-, metal ion-, light-sensitive, as well as readily oxidizable by ascorbic acid oxidase, vitamin C is selected as the most frequently measured nutrient to evaluate the nutrients loss during thermal processing. It is generally accepted that if vitamin C is well preserved, the other nutrients are also well retained. Higher retention of vitamin C in processed products is highly desired. Herein this chapter reviews the degradation mechanism and kinetics of vitamin C of fruits and vegetables during thermal processing, such as blanching, drying, cooking and frying. It starts with an overview of the functions of vitamin C in human’s health. Then the current status for understanding of the degradation kinetics of vitamin C during thermal processing was outlined, followed by the discussion of its degradation mechanism. At last, potential strategies or alternatives to keep vitamin C are identified and discussed.

Abstract

Design, operation and optimization of dryers demands the calculation of energy consumption, in most cases in the form of thermal energy, equipment sizing, temperature and moisture distribution of solids as well as temperature and humidity distribution of drying air. Energy calculations are very important as drying is a widespread process in a variety of industries and is highly energy demanding. In the energy analysis of the process the first step is the estimation of the minimum energy requirement followed by the estimation of energy rejection through solids stream and especially through drying air. Increase of thermal efficiency is always willing and the two most common ways for its achievement is the application of heat exchange between cold feeding air and relatively hot rejecting drying air and hot air recirculation. The later is also employed for the adjustment of air temperature and humidity gradient through the dryer. The combination of a heat pump with the dryer decreases considerably the thermal energy consumption but demands electricity and the method can be beneficial in cases of excess electricity production in the process plant, e.g. by cogeneration. Utilization of exhaust hot air from the main drying unit for the predrying of wet solids can also decrease the total energy requirement. The application of humidity adsorption from the feed air increases its drying potential, but regeneration of adsorbent is required. Grand composite curve of the process plant can reveal potential heat sources from different unit operations.

Abstract

The increasing interest in polyphenolic compounds in industries has led to the exploration and exploitation of rich bio-compounds from natural sources, essentially plants and their by-products. Solid-liquid extraction is mostly applied for the recovery of these valuable compounds from plants. Since the extraction process is often difficult in a fresh matrix, a drying operation is needed to reduce the moisture content, and preserve the targeted valuable compounds. An uncontrolled drying operation will lead to product damage and hence, loss in quality, reason why, several studies have been carried out to understand and control the drying process. The present chapter aims to present some data on drying for bioactive compound recovery from plants and their by-products, mainly polyphenolic compounds. Our main interest is the mathematical tools used to model the drying process.

Pesticides offer one of the best means of controlling plant diseases and pests and subsequently improving the yield. They have been used since the 19^th century. Pesticides, undoutly are poisonous and their indiscriminate use and abuse may result in ecological imbalance resulting in pest resurgence, aggravation of minor pest, pesticides resistance, environmental pollution, poising serious health hazards to man and animals. However, if used judiciously, following the guide line of Pesticide Action Network (PAN), such problems are not likely to occur, and instead improve crop yield. It is however unfortunate that many of us really lack the insight in Materia Medica of plant diseases and pests and most of the problems have occurred due to misuse and abuse of pesticides for which man is responsible and not the pesticides.

A pesticide is any material intended to prevent, destroy, repel, or mitigate any pest, which is defined as a living organism that occurs where it is not wanted or that causes damage to crops, humans, or other animals. There are many different types of pesticides, each is meant to be effective against specific pests. The term “-cide” comes from the Latin word “to kill.”

A pesticide may be referred to by several different names, which can cause confusion. The same pesticide may be referred to by a number of different names, or different pesticides may have similar names.

Advantages of Using Pesticides

Pest are an ecological problem and therefore our control strategy must be ecologically sound. Modern agriculture is a combination of both and human intervention is necessary, whether it be pulling out weeds by hand, use of pesticides or genetic engineering. Control methods evolve over time as knowledge and techniques improve. This includes the development of chemical means of control which become very important because of a number of advantages

Pest are an ecological problem and therefore our control strategy must be ecologically sound. Modern agriculture is a combination of both and human intervention is necessary, whether it be pulling out weeds by hand, use of pesticides or genetic engineering. Control methods evolve over time as knowledge and techniques improve. This includes the development of chemical means of control which become very important because of a number of advantages

There are broadly five categories of crop protection products

Insecticides: Insecticides provide protection to the crops from the insects by either killing them or by preventing their attack. They can be further classified based on their mode of action:

The Insecticides Act, 1968 and Insecticides Rules, 1971 regulate the import, registration process, manufacture, sale, transport, distribution and use of pesticides with a view to prevent risk to human beings or animals and for all connected matters, throughout India. However, recently the Union Cabinet gave its approval for the introduction of the Pesticides Management Bill with the aims of improving the quality of pesticides available to Indian farmers and introducing new, safe and efficacious pesticides. This bill will replace the existing Insecticide Act 1968.The pesticides’ regulations in India are governed by two different bodies:

Pesticide Formulation

Pesticide formulation is the process by which the pesticide is put into a form which can be easily produced, stored, transported and applied by practical methods in order to achieve a safe, convenient economic and effective method of pest control.

When a pesticide active ingredient (a.i) is manufactured, it is not in a usable form as it may not mix well with water or may be unstable. Therefore, it is mixed with other compounds to improve its effectiveness, safety, handling and storage. These other compounds can include solvents, mineral clays, stickers, wetting agents, or other adjuvant. The mixture of a.i. and inert (inactive) ingredients is called a pesticide formulation. Some formulations are premixed while others must be mixed before use. A single a.i. is often made into several formulations.

When two or more chemicals can be used in combination or mixed safely, they are said to be compatible. These combinations can be a pesticide mixed with another non-pesticide chemical, or can be two or more pesticides that are combined in the same tank mix. The reasons for combining pesticides are:

1.To control different types of pests with a single application. Often, several types of pests need to be controlled at the same time. It is generally more economical to combine the pesticides needed and make a single application.

2.To provide superior control than that obtained from one pesticide. Applicators at times combine active pesticides to kill a pest that has not been effectively controlled by either chemical alone. Many combinations are quite effective, but in most cases it is not known if the improved control is a result of an additive effect or a synergistic action of the combined chemicals on different segments of the pest population. One should always check the label prior to verify the safety and legality of mixing pesticides.

3.To increase the effectiveness of one of the chemicals. As mentioned above, this is called synergism. The material added to increase the effectiveness of the primary chemical is called a synergist. The synergist may not necessarily be pesticidal by itself, but increases the effectiveness of the pesticide with which it is combined.

Tank mixing two or more pesticides saves time and labor and reduces equipment and application costs. In some cases, however, it can alter the effectiveness of one or more of the products. Two or more pesticides are considered compatible when they can be mixed and applied in combination without adversely affecting the effectiveness or the physical and chemical properties of the mixture, or causing undesirable damage to the application site. When problems develop from mixing two or more products together, the chemicals are considered incompatible.

Incompatibility

Incompatibility is a condition that prevents pesticides from mixing together properly to form a uniform solution or suspension. The formation of flakes, crystals, or oily clumps, or severe separation is unacceptable. Such incompatible mixtures clog application equipment and limit even distribution of the active ingredient in the spray tank. This prevents good pesticide coverage. The cause of incompatibility may be the chemical nature of the materials you are mixing. Impurities in the spray tank or water also may affect compatibility. Even the order in which you mix pesticides in the spray tank is important. Sometimes the types of formulations being mixed influence compatibility. Pesticide formulations of the same type are rarely incompatible with one another because they usually contain many of the same inert ingredients and solvents. Incompatibility can be a matter of timing or placement of the pesticides. Chemical or physical incompatibility may occur between the pesticides.

The label on the pesticide container is the principal source of information about a product. The label has all the fundamental information that is required. If you need information about a pesticide, do not rely on memory as it is very easy to make a mistake. Read the label every time before using a pesticide. The lay-out of the pesticide label varies between countries. However, every label on a pesticide container from a reputable manufacturer or source will have the following information:

Pesticide Resistance

Resistance to pesticides may be defined as ‘a heritable change in the sensitivity of a pest population that is reflected in the repeated failure of a product to achieve the expected level of control when used according to the label recommendation for that pest species.

The pesticides-one amongst the most important inputs in the crop production contributed a lot to minimize the losses to crop yield. In India, on an average, 33 % of crop loss occurs due to pests and disease and runs to an estimated Rs 1.40000 crore. Pesticide is an essential in the farmers struggle to protect their crops. Pesticides consumption in India reported to 288g/ha is very low compared to global average of 900g/ha. Excessive, irrational and indiscriminate use of these pesticides causes many negative consequences, mainly the famous 3 R viz; Resistance, Resurgence and Residue aspects.

At times a pesticide application fails to reduce the levels of a pest. Usually, the farmer blames either the pesticide for this or he thinks that the pests have developed resistance. Though, the usual causes of poor results with an application of a genuine pesticide from a reputable source are:

Pesticide poisoning occurs when a pesticide enters the body and interferes with the vital systems of the body. Symptoms can begin anything from 1/2 hour to 24 hours after exposure. The typical symptoms and signs of pesticide poisoning are:

Pesticides can cause three types of harmful effects – Acute, Delayed and Allergic.

Acute effects: Are those that occur immediately after the exposure, within minutes or hours.

Definition

Adjuvants are chemicals incorporated in a pesticide formulation or added to the tank mix, to increase effectiveness and safety. They generally have no effect on pests in themselves.

There is a common practice of using the terms spurious, counterfeit, misbranded, illegal, sub-standard and others interchangeably and this often creates confusion among scientist, industrialist and extension officer. Spurious and counterfeit pesticides are the two major words used to describe all kind of anomalies in the pesticides. Hence, there is a need to have a clear understanding of these and differences between them.

Environmental protection Agency (EPA)has established category of pesticides called “Reduced Risk” pesticides to encourage the development, registration and use of products which could result in reduced risks to human health and the environment. New Generation pesticides are considered for “Reduced Risk” status if they have at least one or more of the following status: low risk to human health, low toxicity to non target organisms, low potential to contaminate ground water, surface water or other valued environmental resources and have the potential to expand the adoption and effectiveness of IPM.

Strobilurins are a group of chemical compounds used in agriculture as fungicides. They are part of the larger group of QoI inhibitors, which act to inhibit the respiratory chain at the level of Complex III.Some common Strobilurins are azoxystrobin, kresoxim-methyl, picoxystrobin, fluoxastrobin,oryzastrobin, dimoxystrobin, pyraclostrobin and trifloxystrobin. Strobilurins represented a major development in fungus-based fungicides. They were extracted from the fungus Strobilurus tenacellus. They have a suppressive effect on other fungi, reducing competition for nutrients; theyinhibit electron transfer inmitochondria,disrupting energy metabolism and preventing growth of the target fungi. Strobilurins are miracle fungicides ever developed with novel mode of action & mobility that qualifies the Unique New Generation Fungicides controlling Pathogen from diverse class.

Definition

“Biological pesticides”, or “Biopesticides” as the name suggests, are naturally occurring substances that biologically control harmful pests, especially among field crops. These are naturally produced bio chemical materials basically non-toxic to the environment that can be employed in pest control. Biopesticides could mean living organisms (bacteria, virus, and algae), their products (biochemicals produced by them) and also plant byproducts. Biopesticides offer an ecologically effective solution to the harmful effects of synthetic pesticides.

Pesticide Toxicity

Chemical tactics to manage pests can include many types of compounds. Some merely repel or confuse pests. Some interfere with weed photosynthesis, insect molting processes or development in some way. Others, including some botanical and most conventional insecticides are broadly toxic to living systems. The term pesticide literally means “pest killer". Generally speaking, when using pesticides, we are trying to garner the advantages of using pesticides while minimizing the risk to humans and other non-target organisms. Risk to humans of pesticide use is often described as:

Pesticides sustain food production and control disease and pests. They are vital for crop production and instrumental in continuous increase in food production. The consumption of pesticide in India is one of the lowest in the world. India uses a low amount of 0.5 kg/hectare pesticide compared to 7.0 kg/ hectare by USA, 2.5 kg/hectare by Europe, 12 kg/hectare by Japan and 6.6 kg/ hectare by Korea. However, despite the low consumption of pesticides, India has more problem of pesticide residues vis-a-vis other countries and these have entered into food products and underground water because of

Before applying fungicides in field at large areas, it is required to be thoroughly investigated under laboratory conditions for its efficacy on pathogen, subjected. Basic methods of testing these chemicals against subjected pathogen, under laboratory conditions are described here.

1. Poisoned Food Technique

Principle

The principle involved in this technique is to poison the medium with fungicides and then allow a teat fungus to grow on such medium. The test may be conducted both on solid and liquid medium.

1. Bordeaux Mixture

It was invented in the Bordeaux region of France by PM Millardet (1982).

Also called Bordo Mix.

Mixture of Copper sulfate (CuSO₄), Slaked lime and Water.

It is known locally in France as Bouillie Bordelaise.

Antibiotics are substances which are produced by micro-organisms and which act against micro-organisms. It is also defined as secondary metabolites produced by microorganism, which inhibits the growth of another microorganism. Most antibiotics known uptill now are products of actinomycetes and some are from fungi and bacteria. The use of the antibiotics in managing plant diseases, particlulaty the disease caused by bacteria, mycoplasma and ricketsia, is well demonstrated and are thought to be effective means because of their selective action directed towards causal agents not to the infected host. The mode of action of the antibiotics varies depending on site of action which in turn detrmines their specificity towards given target host (Table 12). Some time mixture of antibiotics are in practice in managing the diseases to reduce delay the chances of resistance development against a particular antibiotic by the causal agent. The most useful antibiotic mixture is streptocycline, which contains streptomycin and tetracycline.

The behavior of pesticides is dependent on many factors, so be sure to consider everything from light and temperature to moisture and pH and recognize that all the factors will impact the active ingredient. Here is some information on these topics, and others, which will improve pest management success.

1.Identification: The first step to disease and pest management success is the proper identification of the insect, disease or weed pest. Without identification of the pest, controls may be misused or improperly timed.

2.Time of Application: Time of application of pesticides plays major role in optimizing pesticidal performance. Early morning or late afternoon are the best times to spray. Dust formulations should be apply in early morning hours (6 am).In the case of foliar spray, it should be done in morning hours between 8 am to 11 am. Avoid spraying during the heat of the day.

3.Water Quality and pH: Primary factors important in water quality are pH and alkalinity (bicarbonates). Most of the pesticides show high efficiency in slightly acidic to slightly basic water pH (i.e. 6.5 to 7.5). Many water sources in alkaline pH (<7.0). Alkali pH (7.5>) is always harmful for pesticides. High pH levels are responsible for alkaline hydrolysis, a process that breaks down the active ingredient in many insecticides, fungicides and herbicides.Add a buffer agent to lower spray solution to a pH of 5.5-6.5. This will give better initial knockdown and longer residual action.

The Effectiveness of a Pesticide in Controlling a Disease and Pest Depends on

Using the right pesticide for the target disease & pest.

Applying the pesticide at the right time.

Applying the pesticide in the right amount.

Applying the pesticide to the right place.

Sprayer is an equipment in which the spray fluid is broken up into fine droplets and ejected under pressure. Actually, the function of the sprayer is to provide the spray fluid with some energy so that it can be broken into fine droplets through the nozzle and propelled to the target. The energy can be produced manually or with the help of any other source of power. There are a variety of sprayers.

Type of Sprayers: There are a variety of sprayers.