eChapters

U value: U value is a measure of the heat transmission through a building part (wall or window) or through a given thickness of a material (insulation). U values with lower numbers indicate better insulating properties.

UHT milk: This milk is homogenized, heated to atleast 135^oC for about 2-3 second, cooled rapidly and then packed in sterilized containers aseptically. The milk in packs can be stored for several months without refrigeration. The nutrient loss is negligible. Used for making yogurt commercially as it does not need to be boiled again.

UHT pasteurization: The milk is heated to ~150^oC for a fraction of seconds practically no holding period. It is also called ultra pasteurization.

UHT sterilization: It is method in which food is sterilized, cooled and then aseptically placed in previously sterilized containers which are subsequently sealed in an aseptic environment.

Ultimate analysis: It is used for determination of a particular element or a compound in a food material.

Ultra heat treated milk: It is designation of the milk sold for liquid consumption after subjection to ultra high temperature to sterilize the milk by killing bacteria and other microbes including spores.

Vacreation: The pasteurization of the milk or cream under reduced pressure by direct steam is called vacreation.

Vacuum: The state of negative pressure. It is equal to atmospheric pressure minus absolute pressure.

Vacuum cooling: A technique of cooling vegetable (leafy vegetables, asparagus, brussels sprouts) having a high surface to volume ratio; rapidly and uniformly by boiling off some of their water at 1⁰C and at low pressure (5 mm of Hg) into a sealed container. The produce is cooled by evaporation of water from the tissue surface and is more rapid than hydro cooling.

Wafer: A thin crisp cake, candy, cracker or chips is known as wafer.

Waffle: A crisp cake of batter baked in a waffle iron is called waffle

Warner-Bartzler Shear: It is one of the oldest but commonly used devices used to measure the tenderness of meat. It is used to test the quality in the cooked meat

Xanthan gum: It is a polysaccharide that is produced by fermentation of carbohydrates by a gramnegative bacterium (Xanthomonas campestris) and is a thickening and suspending agent used in pharmaceuticals and prepared foods. It is also called xanthan. Xanthan is a stabilizer produced by Xanthomonascompestris(Plate 257). Xanthan is not hydrolysed or degraded by humans.

Yabby: It is one of the burrowing Australian crayfishes (Cherax destructor) that are used for food.

Yakitori: A bite-size marinated pieces of beef, seafood, or chicken on skewers is called yakitori.

Yam: It is edible starchy tuberous root of plants (genus Dioscorea of the family Dioscoreaceae) used as a staple food in tropical areas.

Yautia: It is one of the aroid plants (Xanthosoma sagittifolium) chiefly of tropical America with starchy edible shaggy brown tubers that are cooked and eaten like yams or potatoes.

Yearling mutton: Meat obtained from 12-20 month aged sheep. It is also called Earling mutton.

Yeast: Unicellular plant body, very minute in size containing cell wall, cytoplasm with one or more vacuoles and a single nucleus, cause alcoholic fermentation (Plate 258). Yeast usually has little or no mycelium, and reproduces by budding. It results in production of yellowish surface froth or sediment that occurs in saccharine liquids (fruit juices) in which it promotes alcoholic fermentation, consists largely of cells of a fungus (as the saccharomyces, Saccharomyces cerevisiae), and is used in the making of alcoholic liquors and as a leaven in baking.

Zeatin: Zeatin is a cytokinin C₁₀H₁₃N₅O first isolated from the endosperm of Indian corn.

Zeaxanthin: Zeaxanthin is an isomer of lutein occurring in fruits and vegetables (spinach and corn) (Plate 260, 261 and 262).

1.1 Introduction

Pomegranate (Punica granatum L.) is a well-known table fruit of tropical and subtropical regions of the world. The Romans received it from Carthage, hence the name of the genus Punica. Some botanists place it in the family Lythraceae, of the peculiar type of fruit, called as balausta, most authorities make it the only genus in the family Punicaceae. It belongs to genera Punica and family Punicaceae (Chatterjee & Randhawa, 1952; Joshi, 1956). It is a small tree, measuring less than 4 m when cultivated, although it can reach 7 m in the wild. Recent research findings corroborate traditional use of pomegranate as a medical remedy as all parts of this plant have several bioactive metabolites (Holland et al. 2009). Consequently, its demand has increased tremendously not only in the western world but also in other parts of the globe.

2.1 Soil and Climate

Pomegranate grows well in sandy-loam and well-drained soils having a pH of 7.5. It can also be grown on light soils. Quality and colour development in light soils is good but poor in heavy soils. It tolerates salinity up to 9.00 EC/mm and sodicity 6.78 ESP. Even it can be grown well in slightly saline soils as it is considered a saline-tolerant plant (Patil and Waghmare 1983; Rao and Khandelwal 2001; Ram Asrey et al., 2002). Accumulation of salts, in excess of 0.5% of the soil mass causes dying off of growing roots. Interestingly, application of Paclobutrazol (250 ppm) was reported to reduce salinity damage (Saeed 2005). The presence of water-soluble salts like sulphates and chlorides and ex- changeable sodium negatively affect root formation.

3.1 Integrated Insect Pests Management

1. Anar butterfly [Deudorix (Virachola) isocrates Fabricus]

Pomegranate fruit borer or pomegranate butterfly is the most widespread, polyphagous and destructive pest distributed all over India and common in Asia. Peak incidence is during the month of August in monsoon season, while it is more during November/December in winter crop. Infestation from flowering to button stage causing loss up to 50 per cent of the fruit. Adult bluish brown butterfly, female with V shaped patch on forewing. Full-grown larvae are dark brown with short hair and white patches all over the body and measures about 16 to 20mm long. The larvae bore into the pomegranate fruits soon after hatching. Once inside the fruit, larvae (approx 2cm length) feed on the flesh and seeds.  The bored hole is plugged by the last abdominal segment of the larva. When fully grown, the larva comes out by boring through the hard shell and spins a web, which ties the fruit, stalk to the main branch. Offensive smell and excreta of caterpillars coming out of the entry holes with excreta stuck around the holes. The fruits rot and drop off. The holes ultimately expose the rest of the fruit to disease, and typically rot off the tree.

4.1 Harvesting

Pomegranate being non-climacteric fruits should be picked when fully ripe. Its fruits become ready for picking 120-130 days after fruit set. Mature fruits should be immediately removed from the plants as delay in harvesting leads to fruit cracking. Fruits harvested at a premature stage have poor keeping quality and are prone to damage during handling and transport. The fruits are harvested when outer rind becomes yellowish and the fruit when tapped produces a metallic sound. The round fruits become flattened from all the sides and basal beak shaped portion shrinks at the time of maturity. Fruits are harvested with the help of secateurs by retaining 1 cm stalk with the fruit. All the fruits should be harvested in 2-3 pickings within a span of one month.

5.1 Present Status

Export of pomegranate has decreased in quantity from 36,027.43 tons in 2012-13 to 20,997.02 tons in 2014-15, whereas in value term it show an increase trend during the same period. There is tremendous potential for exports of pomegranate from India and it is fact that India is largest producer of pomegranates in the world. Moreover, India produces finest edible quality of pomegranates which are available almost throughout the year. The major Markets of India’s pomegranate during the year 2014-15 were UAE, Nepal, Saudi Arabia, Kuwait and Netherland.

6.1 Strength of India
    ·    In India, pomegranate is cultivated over 1.31 lakh ha with a production of 13.46 lakh tonnes and a productivity of 10.27 t/ha. 
    ·    India is the largest producer of pomegranates in the world.
    ·    Pomegranate is currently ranked 10th in terms of fruit consumed annually in the world. India is the only country in the world where pomegranate is available throughout the year i.e. From January to December. It is cultivated in 3 seasons (Ambia bahar, Mrig bahar and hasth bahar) in Deccan plateau of India. 
    ·    India is endowed with wide agro climatic conditions that offer immense scope for cultivation of various kinds of fruit crops. This provides an excellent platform for the country to emerge as a leading producer of fruit crop. 

Veterinary public health deals with the contributions of veterinary medicine to public health. It is concerned, in the first instance, with the control and elimination of zoonoses and also with the following areas of activity:
    ·    Food hygiene (production, processing and distribution of foods of animal origin)
    ·    Environmental contamination and degradation by animal wastes and animal products
    ·    Comparative medicine (eg. Studies in animals on naturally appearing cancer, cardiovascular disease, metabolic and other disorders encountered in humans)
    ·    Laboratory animal medicine
    ·    Education and training in VPH and communication with the public
    ·    Reproduction biology
    ·    Aspects of mental and societal health
    ·    Emergency veterinary functions in natural disasters and other catastrophes.

Life forms are composed of one of two basic cell types : Eukaryotic or Prokaryotic. Generally, eukaryotic cells are larger and more complex than the prokaryotic cells and possess a membrane-enclosed nucleus; eukaryotic means ‘true nucleus’ (eu=true; karyon = nucleus). All plants, animals, fungi, protozoa and algae are composed of eukaryotic cells. Only the microorganisms classes as bacteria and the archaea are prokaryotic cells. Prokaryotic cells have no nuclear membrane and therefore lack a true nucleus. The latin prefix pro means ‘early’ and in this instance suggests the somewhat primitive nuclear structure found in bacterial cells. Eukaryotic microorganism are sometimes simply referred to as eukaryotes, and the prokaryotic microbes as prokaryotes.

The term growth as applied to higher organisms such as animals commonly is concerned with increase in protoplasmic mass and does apply to reproduction or to increase in number. In microbiology the term refers to increase in the number of organisms. Bacteria increase in number by a process of simple binary fission. Each cell increase in size and redivide into two similar cells. Each of the divide cells may in turn divide to become two cells. Each division produces what is termed as new generation of cells, theoretically there are 2,4,8,16,32,64,128,256 cells in the 2,3,4,5,6,7,8,& 9th generation, this is known as logarithmic growth – the population doubles with each successive generation. Under favourable conditions, bacteria produce generation within 15min. Under unfavourable conditions 24 hours of more may be needed for each generation. Generation time for E.coli is 17 to 20 minutes.

The sources of contamination of milk on the farm can broadly be categorized as

    a)    Interior of the Udder
    b)    Exterior of the Udder.
The interior reflects the health of the animal, while the exterior depends on the farm condition, equipment, persons, water etc.

a) Interior of the Udder
The animal by itself is one of the most significant contributors of microorganism in milk. The bacteria in the udder usually enter from the teat opening and get distributed internally by their own growth and physical movement. In the normal healthy udder, the types encountered in milk are most predominantly Micrococci, followed by Streptococci, Corynebacterium and others. Most of the bacteria are excreted in fore milk.

The Concept of ‘Clean Milk’ Production

Although milk is nature’s most ideal and perfect single food both for the newborn and the mature human beings, the possibility of it being a source of biological and chemical hazards cannot be excluded. In view of the immense dietary importance of milk, the need for production of safe, clean and wholesome milk is emphasized. The term ‘clean milk’ does not mean milk in which all visible dirt is absent or milk from which it has been removed; rather it does denote raw milk from healthy animals, that has been produced and handled under hygienic conditions; that contains only small number of harmless bacteria and that possesses a good keeping quality without being treated by heat. In other words, the unhygienic production of milk may lead to inferior keeping quality as a result of rapid microbial multiplication under favourable storage conditions apart from serving as a potential health hazard. These microorganisms cause the milk to sour quickly, putrefy and develop undesirable flavours, colour defects, ropiness and bitterness. On the other hand, the pathogenic microorganisms, which may gain entry through various sources, may cause many diseases to the consumers.

In India, the collection, transport and distribution of raw milk involves a number of agencies and persons at rural and urban level – village producers, milk collectors, halwais (Sweet-makers), milk vendors, dairies, producer-retailers and wholesale or retail markets.

1. Collection

Usually, the milk collectors approach the small village producers to collect milk and the same is sold directly or indirectly (through agents) to a dairy (milk procurement centres) or halwais or city milk vendors or consumers. The producer – retailers themselves, in some cases, supply the milk to the above said parties. The production of milk in small, scattered holdings in village causes problems during its collection. It involves visits to many villages, some of which are not easily accessible for the purpose.

Starters are selected strains of micro-organisms deliberately added to milk during conversion into cheese, dahi, yoghurt and other fermented dairy products to bring about specific changes in the appearance, body, texture and flavour characteristics of the desired final products.

Functions of Starters

The primary function of almost all starter culture is to develop acid in the product. The secondary effects of acid production include coagulation, expulsion of moisture, texture formation and initiation of flavour production. In addition to these, the starters also help in imparting pleasant acid taste, conferring protection against potential pathogens and providing a longer shelf life to the product. These bacteria convert 1% of lactose in milk approximately to lactic acid with very little by-products such as acetic acid, ethanol, CO2 and normally with no substances causing taints and hence leading to a clean and wholesome milk souring.

Milk fermentation is process by which a change is produced in milk through the activity of microorganism. As milk leaves the udder it serves as a medium for the growth of many species and accordingly undergoes a series of changes, the processes producing these changes constitute the milk fermentation.

Fermentation of organic compounds, especially in the lack of oxygen leads to the rapid break-down of ‘biopolymers’ to produce ‘anaerobic food chains’.

Bacteriophage is the term applied to bacterial viruses. Bacteriophage having the ability to lyse certain sensitive living cells. Phages are small particles, which can only be seen in the electron microscope after the application of suitable staining techniques. All phages have a head and most have a tail. The head may be isometric or prelate with a hexagonal outline.

There are two types of phages virulent and temperate which enter a different relationship with the host, the lytic and lysogenic cycles respectively.

The significance of milk in human nutrition is now well established as it is considered as the best, ideal and complete food for all age groups. However, in spite of being so, milk can also serve as a potential vehicle for transmission of some diseases under certain circumstances. Moreover, by virtue of possessing almost all the essential nutritional factors, milk can also serve as an excellent culture and protective medium for certain microorganisms, which may include potential pathogens capable of causing serious health problems to the consumers. In this way, milk may serve not only as a vehicle of transmission of disease causing organisms, but it can also allow these pathogens to grow, multiply and produce certain toxic metabolites, thereby making itself an extremely vulnerable commodity from public health point of view.

According to International Dairy Federation(IDF),1980, Mastitis also called as ‘mammitis’ is defined as an inflammation of the udder, almost always of microbial origin and is the outcome of a local or a general infection. The common symptoms are related to inflammation, viz., swollen, hot, red, and painful udders. Mastitis can be classified based on symptoms or on the causative organism.

A) Forms of mastitis based on symptoms

    1.    Acute or clinical
    2.    Sub-acute or subclinical
    3.    Chronic.

Tuberculosis

Tuberculosis has been recognized as one of the most important infectious diseases in the world because of its high global impact and its chronic debilitating character, particularly in the poor section of society. Milk-borne tuberculosis is directly or indirectly related to the consumption of raw milk from infected dairy herds.

Normally raw milk contains different levels of inhibitory substances, which restrict the normal development of bacteria and some times may even kill them. The degree of inhibitory activity varies considerably in milks of different species, viz, cow, buffalo, human. Maximum activity present in human milk, variations occur in the milks of individual animals and some times even at different milking or from different quarters of the udder of the same animal.
There are two groups of antimicrobial substances present in milk:
    1.    Inherent or naturally occurring substances in milk. 
    2.    Non- inherent compounds secreted into milk from other sources.

Dairy equipment and utensils with which milk and milk products come into contact are the main sources of contamination in the products. By the use of effective equipment cleaning and sterilization methods on routine basis, milk of high bacteriological quality can be consistently produced. In composite milk plant, a variety of equipment and utensils are used. The use of stainless steel for the fabrication of dairy utensils and equipment provide highly polished and hard smooth surface that can be cleaned readily, apart from showing resistance to corrosive action of detergents and bactericidal solutions. Utmost care is taken to avoid dents and scratches, which could be the possible focal points of subsequent contamination. To overcome all these problems aluminium and stainless steel vessels and equipment present an ideal situation.

Introduction

Numerous characteristics of food determine its acceptability to consumers and to regulatory officials. Before accepting a food for consumption, it must be attractively presented, must have desirable odour and flavour characteristics and other qualities and must be free from potential pathogens or their toxic products. The ultimate nutritive qualities, flavour and appearance have been preserved and no harmful organisms or substances are present to affect the consumer adversely. If the quality of the product is good, its keeping quality is also likely to be substantial. Conversely, there are more chances of spoilage of an inferior quality food product during storage.

India

Milk legislation and regulations are designed to prevent fraud and adulteration. But they now cover many factors that affect sanitation and public health. Milk generally is classified into grades according to the care with which it is produced.

Abstract
 
Food products can have moisture content as high as 90% which needs to be lowered to acceptable limits to prevent microbial growth and deteriorative reactions. Drying is one of the most common and cost effective techniques for removal of excess moisture from the food by application of heat. In addition to its role of extending the product shelf life and providing stability, drying also helps to produce variety of products from agricultural, horticultural and industrial products. But to obtain the desired quality product, adequate drying is essential which depends on type of dryer and drying technique employed which further requires proper understanding of drying process. Despite being important unit operation in food processing industry, appropriate scientific knowledge of the drying process is still limited. So, the fundamental principles and associated terminologies with drying has been discussed in detail in this chapter to have thorough understanding of the drying process. In addition, different models and calculation procedures for drying of different types of commodities has also been reviewed.

Abstract

Classification of the hundreds of possible dryers is essential to the logical selection of appropriate dryer for a given application. Diverse criteria for classification as well as selection of dryers are presented and discussed briefly. The advantages and limitations of different dryer types must be taken into consideration. Initial capital cost is often the key deciding criterion in industrial dryer selection. This is not a good strategy as the user must pay for the operating costs over a long period of life of the dryer. In general several different dryer types are suitable for a given product. Careful selection is essential for cost-effective operation of the dryer.

Abstract

Osmotic dehydration is gaining popularity due to several energy and product quality related advantages it offers. It has huge potential as a complementary process step prior to operations such as air-drying, microwave drying, freezing, frying etc, if not an alternative one, in the food process chain. It can be easily integrated with other processing steps in order to improve the overall efficiency of a given food process. Application of additional driving force either prior to or during osmotic dehydration can enhance the mass transfer rates in the osmotic dehydration. Role of mathematical modelling both in osmotic dehydration and rehydration have been discussed. Current limitations for the adaptation of osmotic dehydration in the food processing industry and possible solutions are also discussed in detail.

Abstract

Spray drying is one of the most preferred methods of converting food and pharmaceutical solutions into powder form. Very high product throughput, hygienic and highly automated process and relatively benign thermal and dehydration stress on products associated with this process has made it ubiquitous in powder manufacture. Compared to freeze drying, spray drying is significantly less expensive both in terms of operation and capital costs. In this chapter, key features of spray drying such as underlying operational principle, types of spray nozzles used, the flow pattern of droplets/particles and drying medium within the drying chamber, the particle formation process of individual droplet are discussed in considerable detail. The modelling aspect of a single droplet subjected to spray drying environment has also been included. Finally, the most commonly considered characteristics of spray dried powders including morphology, crystalline/amorphous nature and solubility are highlighted and discussed.  The content presented in this chapter will be very useful for practising engineers, technologists, researchers as well as postgraduate and undergraduate students.

Abstract

Hot air circulation is the most common industrial method of drying foods which has its own inherited disadvantages. Microwave drying can be an alternative method for removing moisture from foods and there has been a surge of interest in the application of microwave to process the foods, in past few years. The reason being that there is worldwide energy crisis and the growing acceptance and familiarity with domestic microwave ovens. It is well known that conventional means of heat processing irreversibly alter the flavor, colour, and texture of many foods. From the point of flavor alone, it is desirable to improve our present methods of processing foods. Some improvements have been made in this direction with a number of food products by use of high-temperature short- time processing.

Abstract

In recent years microwave processing have attained increasing recognition in food industries particularly in drying and dehydration. During microwave processing, electromagnetic energy is supplied directly to the food material for volumetric heating. This provides rapid temperature rise throughout the material with reduced thermal gradients. This unique heating mechanism reduces processing time and saves energy. In-spite of advantages of microwave heating it leads to overheating in food material and formation of cold and hot spots if applied improperly during drying. To overcome these challenges different microwave assisted hybrid drying technologies have been developed by many researchers. These techniques are microwave assisted hot air drying, microwave assisted osmotic dehydration, microwave assisted vacuum drying, microwave- infrared assisted hot air drying, microwave assisted rotary drying. This chapter comprises the fundamentals of microwave and provides comprehensive update of microwave assisted hybrid drying processes for food and agricultural materials.

Abstract

Drying is a very important unit operation in food processing. Being an energy intensive unit operation, drying process demands improvement to make it energy efficient. Beside this operating conditions used in drying affect product quality substantially; however, traditional dryers do not allow enough flexibility to meet quality requirements for several products. This has resulted in development of number of new drying techniques, to cope with both energy efficiency and product quality.

Abstract

The objective of this chapter is to provide an overview of heat pump dryer (HPD) and recent developments in its applications for drying of agricultural and food products. The basics of heat pump dryer, classification, operating principle, configuration and control system have been presented for better understanding. Many researchers have concluded that HPDs use energy more efficiently than electrical dryers. The heat pump dryer is best suited for drying high value commodities such as fruits, vegetables, spices, condiments, herbs, medicinal and aromatic plants at near ambient temperature for producing better quality dehydrated product.

Abstract
 
Grains are usually harvested above 20% (wb) moisture level and they are prone to microbial attack at high moisture level. In order to avoid both qualitative and quantitative losses that arise from microbial growth, grains are usually dried to safe moisture level. The safe storage moisture content may vary from 8-16% (wb), depending upon the grain and climate type. Therefore, drying is a necessary step in preventing these losses. Drying also reduces the bulk weight of the materials, thus easing transportation and storage. Drying can occur in thin layer or in deep bed. Different drying theories are proposed to characterize these drying processes. Theoretical as well empirical drying equations have been developed.

Abstract

Recently, the reduction of post harvest food losses around the globe is a critical issue for ensuring future food security. Drying techniques is important option to prevent losses and preserve food for long time. The solar thermal energy required to remove moisture from the food during the drying process can be optimized by designing suitable solar dryers. Moreover, the application of solar energy in drying of agricultural products has tremendous potential, since it can easily provide the low temperature heating required for drying and helps in reduction of CO2 emissions. Hence, the present chapter deals with descriptions of different types of solar dryers used to dry various types of agricultural food products and design of solar dryers. Also, the heat and mass transfer parameters with respect to various process variables to estimate the performance of the food dryer system were analyzed. The advantages of solar dryers in terms of net CO2 emissions mitigation potential and the quality attributes of dried food products are also discussed. It is suggested that properly designed solar dryers having low operational cost compared to electrically heated dryers may prove to be an energy saving device for drying of agricultural products. However, the techno-economical and environmental aspects of various efficient solar dryers are needed to be further studied for applications in various irregular shaped food products.

Abstract

The primary commercial energy sources such as coal, oil and natural gas poses an enormous challenge to our development goals including environmental degradation, as India is not well endowed with these exhaustible natural resources. Further, these conventional sources are also not available in right quantity and producing environmental pollution manifold in land, air and water. There are number of unit operations in food processing and value addition consuming bulk of conventional energy sources where renewable energy sources can easily be integrated for energy conservation and environment protection. There is significant potential for application of Renewable Energy Sources in different unit operation of food processing including drying of food products for energy conservation and for reducing hydrocarbon emissions.

Abstract
 
Drying is one of the most popular methods used for preserving products and extending their shelf lives by reducing moisture content to a low level to prevent microbial spoilage and moisture-mediated deteriorative reactions. As an efficient technology with high heat and mass transfer rates, impingement drying has been commonly used in various industrial drying such as tissue paper, textiles, photographic films, coated paper, nonwovens, carpets, lumber etc. In the past two decades, air impingement technology has got more and more attention in the field of food and agricultural products processing.

Abstract

There are several empirical models to describe deep bed drying dividing the domain into many thin layers. Empirical equations are seen as a resource that only serves to describe the thin layer drying kinetics of an agricultural product. Normally an empirical model is used to determine drying rate. The validity of following thin-layer drying models are accounted by coefficient of correlation (R2), standard error of estimated (SEE), root mean square error (RMSE). The properties of dried foods vary substantially depending upon the type of product, moisture content, drying type and ultimately drying conditions. To take care all above variables, a promising approach is to use Artificial Neural Network (ANN). In process control, the main objectives are food safety, high quality and yield at minimal costs. To obtain high quality products, on-line control techniques are required. Most food processes are highly nonlinear, with time varying dynamics, which complicates food automation. However, the recent developments in artificial intelligence based advanced control tools such as ANN to food processing have opened up novel possibilities for processing industries.

Abstract

Food dehydration is an oldest method to increase the shelf life of food by reducing the water activity. A dried food product provides advantages of increased shelf life and reduced cost due to decreased weight as well as transportation. However, there is a decrease in product quality due to inadequate control on drying process parameters such as drying temperature and moisture removal together with change in thermo-physical properties of food. Computational modeling and simulations can provide a unique insight on the drying parameters that influences the product quality, and optimize the process conditions which are difficult by experimental analysis. Moreover, the computational techniques are advantageous over experimental optimization methods by minimizing the time and cost. This chapter reviews different computational modeling techniques such as, finite element modeling, finite volume and finite difference methods for modeling of food dehydration process. Also, this chapter describes the application of modeling techniques for determining the influence of shrinkage and porosity during dehydration.

Abstract

It is well known that drying is an important unit operation in food processing industries, essentially used to extend the shelf life but also in making innovative processed products such as snacks with desired functionalities. Although drying of food products is carried out traditionally using several methods, the quality and energy aspects have been major focus of food drying research in the last decade or two. This is achieved by modifying and/or optimizing the existing drying systems, improving pre and post processing of the product, combination of more than one dryer type or developing altogether a new drying technique. There several dryer types which can give extremely good product quality, however, cost-effectiveness can be a major issue. It is necessary to balance both good product quality and minimum energy usage in order to sustain highly competitive market. This lecture will provide an overview of conventional drying methods used for foods, followed by some advances in these conventional methods and a discussion on some new drying techniques developed in recent years that are either commercialized or have potential of industrial use.

Abstract

Drying is an age old practice of food preservation. Removal of moisture from the food materials is usually carried out at atmospheric pressure and elevated temperature. In the presence of oxygen, drying can cause oxidation of some compounds leading to quality deterioration. Drying at higher temperature adds to the losses and can be responsible for enzymatic and non enzymatic browning, loss of aroma, nutrients, antioxidants, pigments etc. On the other hand, drying under sub atmospheric pressure helps in retaining the themosensitive compounds present in natural foods as drying can be accomplished in oxygen free environment. Under vacuum, evaporation of moisture can be possible at lower temperatures.

Abstract

Refractance Window (RW) drying is a relatively new drying technology. This method is carried out by spreading a thin film of food slurry on a conveyor belt made up of a transparent polyester material. The slurry is thermally heated as it moves along the conveyor belt, resulting in rapid drying of the product. RW drying is similar to Drum Drying, but conducted at lower temperatures (95–97^ºC) and without direct contact with the heat source. RW drying offers low operating costs with excellent retention of color, flavor and nutrients.

Abstract

Fruit leather is a concentrated source of nutrient, energy and minerals processed from fruits in the form of sheet or leather. It is eaten as a desert or snack since ancient time. Fruit leathers have a greater benefit than fresh fruits if equilibrium ingredients are established and seasonal surplus of fruits are utilized and contributed to minimize post-harvest losses. The process of making fruit leathers involve making fruit puree and adding additives and preservatives for the purpose of enhancing taste and shelf-life. Drying, the key unit operation in making fruit leathers, is the most energy intensive and time consuming step in the process, modern drying techniques can be implemented to overcome the limitations. By novel means of processing technologies or enrichment could lead fruit leather to introduce high quality food product in the market. Continuous research and development can lead to a new era of production and development of fruit processing and overcome the obstacles during processing. In addition study on chemical and biochemical hazards involved in overall process will guide to ensure product safety. Market research tools e.g. quality function deployment method and other market analysis methods could be applied to understand the product trend, demand, consumer expectations and the scopes of improvement.

Abstract

Medicinal herbs are economically and nutritionally important plants, which are rich in health-promoting compounds. Herbs are the backbone of both the traditional Chinese and Indian medicine, which has long history as part of their culture. Ensuring the quality of herbs is a crucial step for integrating the traditional medicine into science-based modern medicine. Drying is an essential technique in preservation of herbs as it affects directly the quality attributes of the dried products, whereas many producers lose much profit due to poor drying techniques. So, employing a suitable drying technology and selection of appropriate drying conditions are very important for producing high quality herb products. The aim of this article is to summarize the advances in drying technologies of medicinal plants, describe the current status and identify future research opportunities. The current work provides more data and information for selecting optimum technology for herb drying and would trigger innovative drying technologies to enhance drying kinetics and quality of herb drying.

Abstract

Food proteins are among the commonly used ingredients by food manufacturers to produce different products with desired characteristics. Due to several nutritional and functional properties, proteins have different functions in various food products in addition to their role in metabolic system of the human body. Dilute or concentrated solutions of pure proteins or unprocessed food products which are rich in protein are very sensitive to deterioration or degradation by microorganisms and thus have short shelf life at ambient temperatures due to their highly moist structure and high protein content. Drying is one of the best methods that can guarantee preservation, a longer shelf life, chemical or thermal stabilization and resistance against other stresses. A full understanding of stresses encountered during drying is needed to choose an appropriate drying process and to optimize this process for maximum product quality. A number of methods have been used by various researchers to dry protein-containing foods. Among these methods, freeze drying and spray drying are the most common techniques. Sun drying, convective hot air drying, vacuum drying, heat pump drying, radio frequency drying as well as combined or hybrid drying methods with two or more of the drying methods have also been developed.

Abstract

Application of solar energy for drying of agricultural food products is one of the most attractive and cost-effective drying techniques. However, the intermittent nature of the solar energy is one of the major shortcomings of the solar drying system that can be alleviated by storing excess energy during the peak time and using it in off sun hours or when the direct availability of solar energy is inadequate. The use of sensible and latent heat storage systems in solar dryer is an effective way of storing thermal energy for drying purpose. This chapter will present information on different thermal energy storage (TES) materials, their advantages and disadvantages. The information available in the literature regarding the studies conducted on TES assisted solar drying systems is also covered in this chapter. In addition, some of the models that have been used by different researchers to test the performance of different TES materials are also reviewed.

Abstract

Drying remained at the centre stage since the initiation of the food processing due to its promise to preserve agricultural products economically and add functionality to a food product unlike other thermal as well as non-thermal food processing operations. However, many existing drying techniques have their own limitations like nutrient loss, damage of the organoleptic quality, high cost etc. Therefore, research for better drying technologies is going on. Supercritical drying (SCD) is one such technology which utilizes higher dissolving power of super critical fluids (SCFs) to dry food products. The current chapter illustrates the mechanism of SCD as well as current state-of-art and promise of the drying technology. Also, some modelling approach of SCD has been included in the discussion to facilitate new designs and optimization of SCD for various food products.