eChapters

INTRODUCTION

Fruits and vegetables are historically important constituents of human diet and the growing awareness of consumers about the beneficial effects of these commodities could result in enhancement of global trade involving fresh and processed fruits and vegetables. Emergence of postharvest handling of fresh fruits and vegetables facilitated global trade of these commodities. The developed countries started realizing the export potential of these commodities by development of adequate value addition in terms of pretreatments, shelf life extension and packaging besides grading and other associated packing house operations. However, the trade concerning fresh fruits and vegetables could never come out completely from problems related to pesticidal residues, spoilage, bulkiness of the commodities involving transportation of inedible portions and excessive packaging costs arising out of bulkiness. The other problems associated with fresh produce include mandatory requirement of specific storage temperatures with refrigeration as the primary means of regulation of metabolic rate.

INTRODUCTION

Now-a-days, food products with maximum health benefits and ease in preparation are gaining popularity globally, the reason being changing awareness level about food and dietary habits. Since ages, a number of methods like cooking, baking, drying etc. have been used to thermally process the food materials. Electrical sources of electromagnetic waves are very promising because of advances in nuclear and hydroelectric power as well as ongoing cost rises in traditional forms of fuel, of which there are only restricted reserves. The heating aids include use of wooden fuel, gaseous fuel, electric energy etc.; but the new era of electromagnetic rays had introduced new horizons of food processing by utilizing it in various unit operations (Sakai and Hanzawa 1994). Though, these radiations are gaining popularity in various walks of life; their destructive impact is much dominating. Hence, one should handle these radiations with utmost care as well as comprehensive understanding of the know-how and control over the process.

INTRODUCTION

Radiation processing is a promising technology for improving hygiene and increasing storage and distribution life of food products. Ionizing radiation can be used to bring about beneficial changes in food stuffs (Urbain 1995) and it has been suggested as a method of ensuring safety of meat products (Patterson and Stevenson 1995). Ionizing radiation interacts with an irradiated material by transferring energy to electrons and ionizing molecules by creating positive and negativities (Moseley 1989).

INTRODUCTION

Preservation of food by drying or chemical means as by alcohol or acid fermentation and that by the use of ice is long recorded in history. With the advancement of science and the knowledge governing various unit operations in food processing, these food preservation techniques employing thermal, radiation, or low temperature or a combination of these have only got further refined as regards their viability and commercial applications. Process foods of different genre and cuisine, which include frozen foods too, are increasingly becoming popular the world over for reasons of quality, safety and year round supply of nutritious foods to cater to different niche segments of human society. Increasing health consciousness is buoying those processed foods which are preserved and stabilized using non-thermal technologies as these ensure retention of food nutrients to a better definition. Interest in frozen food also stems from need to deliver safe and nutritious foods with extended shelf-lives.

INTRODUCTION

Drying or dehydration is defined as the removal of moisture from its initial level to a level which renders food materials safe for subsequent storage. It is a simultaneous heat and mass transfer operation in which heat is supplied externally to evaporate moisture and air is forced through the bed to carry away the moisture. Drying is the oldest technique to preserve food materials. Advantages of drying include reduction in water activity, enhancement of shelf life, maintenance of flavor and nutritive value, and reduction in packaging and transportation costs. When the water activity of the dried product is reduced to below 0.6, most microorganisms do not grow and the rates of other deteriorative reactions are substantially reduced.

INTRODUCTION

A mixture is a combination of two or more elements or compounds in any proportion so that the components do not lose their identity. Most materials in our world are mixtures and very few materials are pure substances. Foods are complex mixtures of compounds and the extraction or separation of food components is fundamental for the preparation of ingredients to be used in other processes. Separations usually aim to remove specific components in order to increase the added value of the products, which may be the extracted component, the residue or both. Purposes include cleaning, sorting and grading operations, extraction and purification of fractions such as sugar solutions or vegetable oils, recovery of valuable components such as enzymes or flavour compounds, or removal of undesirable components such as microorganisms, agricultural residues or radionuclides. For example, cooking oils from oilseeds or gelatin from connective tissue; or for retrieval of high value compounds, such as enzymes (e.g. papain from papaya for meat tenderisation or rennet from calf stomachs for cheese making). Other types of separation methods are used to sort foods by separating them into classes based on size, colour or shape and to clean them by separating contaminating materials.

INTRODUCTION

The concept of hurdle technology has been developed as a new way to realize safe, stable, nutritious and economical foods. It employs combination of different preservation techniques to achieve a multi-target, mild but reliable preservation of foods. The application of hurdle technology in food preservation is increasing rapidly worldwide. Over the years, insight into the hurdle effect has been broadened and the application of hurdle technology has been extended. A better understanding of the occurrence and interaction of food preservative factors (hurdles) in foods is the basis for improvements in food preservation. If the hurdles for the microbes are known, the microbiological stability and safety of this food might be optimized by changing the intensity or quality of these hurdles. Using the proper combination of hurdles, it is possible to improve not only the microbial stability and safety but also the sensory and nutritive quality as well as the economical aspects of food. The hurdle concept is also referred to as food preservation by combined methods, combined process, combination preservation or combination processing techniques. The hurdle effect is of fundamental importance for the preservation of foods. The illustration of hurdle effect was first introduced by Leistner in 1978. Based on the understanding of hurdle effects, the concept of hurdle technology was derived (Leistner 1985).

INTRODUCTION

By the turn of the century, consumers have been more demanding, sophisticated and discretionary. They want much safer, higher quality, and more convenient to foods. The food processor need to get the best from their existing processing technology in addition to looking for newer ones. New and alternative food processing methods and/or novel combinations of existing methods are continually being investigated by the industry in pursuit of producing better quality foods more economically. Thermal processing is one of the most important food preservation techniques that was first introduced at the beginning of 1800 and has evolved itself in to one of the most scientific mature food processing techniques of recent times. Both science and technology have gone through tremendous transformation in the last two centuries and today it is the most reliable method to assure food safety and stability. Developments in thermal processing and evolution of non-thermal processing technologies like high pressure processing, pulsed electric field, pulsed light etc. have enhanced the utility of thermal processing principles and increased the awareness of possible alternative processing technologies.

INTRODUCTION

Food processing is necessary for the conversion of raw food products in to finished products with desired textural, sensory and nutritional attributes. This is required to be done mainly due to seasonal production and facilitating non-seasonal availability of different commodities. Stages of processing are primary and secondary. In primary processing raw material is converted into food commodities, while in secondary processing commodities are converted into edible products. Processing is mainly done to convert the products into edible forms, to extend shelf life, availability, accessibility and also to provide variety into the form of value added products. Processing of products destroys inhibitors, microorganisms, retards physico-chemical and biochemical deterioration, maintains good sensory properties, preserves and enhances the nutritive value. Unit operations involve phase changes and sometimes chemical reactions also, which are undesirable as they cause inferior quality of the product (Gekas 1992). Different processes like separation, assembly, preservation and packaging are broader classification for unit operations in food processing (Saravacos and Kostaropoulos 2002).

Food Science is one of the ancient sciences and the genesis originates to the very beginning of human civilization. The advent of food science was associated with practice and observation by humans before establishment of scientific concepts. The ancient man knew that roasting or smoking of meat improves the edible quality and digestibility. As a consequence, he started practicing the same much before the reasons for the same could be established. Many of the modern preservation concepts had their origin in prehistoric period itself as humans could use techniques such as dehydration, fermentation and pickling to their advantage to improve the sensory attributes of the products and also to enhance their shelf life. Humans during the Pre-Neolithic period about 2,50,000 years before used fire for cooking meat. During the Paleolithic period humans not only roasted food but also developed grinding, pounding and drying. During the Mesolithic era, humans were desperate for food and got involved in extensive hunting and fishing. During the same time domestication of animals took place and animal husbandry became a reality (Stewart and Amerine 1982). The Neolithic period made qualitative changes in the food habits of humans and they changed from a food gathering and hunting society to one of food production (Heizer and Elsasser 1980).

Abstract

Inspired by the human eye to brain assessment process, computer vision technology has demonstrated its potential for monitoring and controlling of several operations in food industry. Computer vision technology is, therefore, applied extensively in food drying process for monitoring nutritional value and sensorial characteristics because of its promising characteristics such as reliable objectivity and repeatability. In this chapter, after providing a brief explanation of the computer vision technology and its prerequisites and principles, an example is given to elucidate how this technology is used for monitoring the visual attributes of foodstuffs during drying process. Overall, monitoring the visual properties of food products like size, shape, color, and texture in off-line mode are the most popular issues to fascinate researchers’ attention to apply the computer vision technology in food drying. Nevertheless, industrial applications of the computer vision technology for real-time monitoring and control of food drying facilities as final goals of its introduction in food drying industry seem to be limited. For future studies, it is suggested to apply this unique technology along with advanced soft computing methodologies for in-line monitoring and control of food drying process in order to achieve high quality dried products. Finally, outlooks and potential employment of this technology in food drying domain are discussed as well.

Abstract

By loosely inspiring the actions of neurons in the human brain, artificial neural networks (ANNs) are widely accepted as a powerful nonlinear adaptive approach to tackle complex, dynamic, highly nonlinear, and ill-defined problems in an increasing number of fields of food industry.They have been used extensively in food drying to solve problems of nonlinear function approximation, pattern recognition, data description, optimization, simulation, pattern recognition, control, data sorting, clustering, and noise reduction, due to their massively parallel structure and capability to learn from examples. In this chapter, after providing a brief description of ANN technology and its principles as well as the structure of the most commonly employed ANNs in this context, an example is given to explain how the ANN technique is used for modeling and controlling food drying process. Generally, modeling, prediction, and optimization of heat and mass transfer, thermodynamic performance indicators, and quality parameters as well as physico-chemical attributes of dried foods are the most popular subjects to attract researchers’ attention to apply the ANNs in food drying industry.

Abstract

Packaging plays an important role in the food processing Industry. It makes food more convenient as well as gives the food greater safety assurance from microorganisms, biological and chemical changes such that the packed foods can have longer shelf life. In order to meet the huge demand of processed food with longer shelf life, various methods of preservation and packaging are being used in the food processing industry. Drying and dehydration is one of the method which helps preservation of a perishable commodity against deterioration or spoilage.

Abstract

Most dryers operate at low thermal efficiency. The development of models and control systems offers an opportunity to improve dryer operation and efficiency. Dryer control is very important and with deeper understanding of the drying concept, new “smart” dryers can be made more reliable and more cost-effective than classical dryers. This chapter will provide an overview of necessity of control and safety measure in food drying system, and terminology related with drying control system. Different control strategy includes conventional and advanced techniques implemented in drying operation are reviewed  here and simple outline of intelligence control system in drying technology are briefly described in succeeding section. Various hazards in drying process and risk and safety management will also be discussed.

Abstract

Water, the most important component of common foods, is considered to be desirable as well as undesirable in the different food systems. Water-solid interaction in food systems controls various biological, biochemical and biophysical reactions affecting their acceptability. The retention or release of water from solid has been quantified in the terms of sorption isotherm. Sorption isotherm techniques have been used to characterize and identify the type of water-solid interaction in different food products. Sorption isotherm provides various information useful in designing and optimization of drying, storage, packaging, predicting quality and shelf life of the product.

Abstract

Dietary antioxidants can be found naturally in various fruits, vegetables and food products.Typically, antioxidant phytochemicals commonly found in food products are Vitamin C, Vitamin E, carotenoids, polyphenols, melanoidins and indoles. The main characteristic of an antioxidant is its ability to scavenge free radicals and form stable end product which inhibit the chain oxidative mechanisms that lead to degenerative diseases which are harmful to human health. Drying is widely used in food processing to minimize food wastage and to extend food shelf-life. Pretreatment, drying methods and storage conditions are some of the processing parameters affecting the quality of dried products. Selection of processing conditions and storage environment are therefore critical in maximizing the retention of food antioxidants. This chapter aims to compile and summarize studies carried out for antioxidants namely antioxidant contents in dried food products, effect of processing parameters and quantification methods in the analyses of antioxidants.

Abstract
 
Spray drying is used as one of the best alternatives for extracting essential constituents of fruit and vegetables. Spray drying of fruits and vegetable juice/purees, which is an excellent source of bio-functional properties into a solid phase helps to enhance their stability and controlled release in different food matrices. Spray drying along with different carrying agents helps to retain essential active compounds in fruits and vegetables. Spray drying is generally carried in three steps viz. atomization of liquid feed by suitable atomizer; drying of droplets with the help of hot air and motion of droplets. Carrier agents like maltodextrin, wax starch, Gum Arabic and microcrystalline cellulose are added to the feed to increase glass transition temperature. Chapter presents the effects of different operating parameters of spray drying as well as effects of carrier agents on the physicochemical and functional properties of spray dried fruit and vegetables powders.

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.

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

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.