Community Nutrition In Action An Entrepreneurial Approach Mobi Download 12
Lang Nunnally
Food preservation involves different food processing steps to maintain food quality at a desired level so that maximum benefits and nutrition values can be achieved. Food preservation methods include growing, harvesting, processing, packaging, and distribution of foods. The key objectives of food preservation are to overcome inappropriate planning in agriculture, to produce value-added products, and to provide variation in diet. Food spoilage could be caused by a wide range of chemical and biochemical reactions. To impede chemical and microbial deterioration of foods, conventional and primitive techniques of preserving foods like drying, chilling, freezing, and pasteurization have been fostered. In recent years, the techniques to combat these spoilages are becoming sophisticated and have gradually altered to a highly interdisciplinary science. Highly advanced technologies like irradiation, high-pressure technology, and hurdle technology are used to preserve food items. This review article presents and discusses the mechanisms, application conditions, and advantages and disadvantages of different food preservation techniques. This article also presents different food categories and elucidates different physical, chemical, and microbial factors responsible for food spoilage. Furthermore, the market economy of preserved and processed foods has been analyzed in this article.
Community Nutrition In Action An Entrepreneurial Approach Mobi Download 12
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Foods are organic substances which are consumed for nutritional purposes. Foods are plant or animal origin and contain moisture, protein, lipid, carbohydrate, minerals, and other organic substances. Foods undergo spoilage due to microbial, chemical, or physical actions. Nutritional values, color, texture, and edibility of foods are susceptible to spoilage [1]. Therefore, foods are required to be preserved to retain their quality for longer period of time. Food preservation is defined as the processes or techniques undertaken in order to maintain internal and external factors which may cause food spoilage. The principal objective of food preservation is to increase its shelf life retaining original nutritional values, color, texture, and flavor.
Conventional food preservation techniques like drying, freezing, chilling, pasteurization, and chemical preservation are being used comprehensively throughout the world. Scientific advancements and progresses are contributing to the evolution of existing technologies and innovation of the new ones, such as irradiation, high-pressure technology, and hurdle technology [3,4,5]. The processing of food preservation has become highly interdisciplinary since it includes stages related to growing, harvesting, processing, packaging, and distribution of foods. Therefore, an integrated approach would be useful to preserve food items during food production and processing stages.
This review paper presents the classification of food items and discusses different physical, chemical, and biological factors of food spoilage. The basics and advancements of different trivial and modern food preservation techniques, which are attributed to impede food spoilage and to yield longer shelf life, are discussed here along with their mechanisms, application conditions, advantages, and disadvantages. This article also reports the global market trend of preserved and processed food. Figure 1 summarizes a flow diagram showing various categories of foods, components of food spoilage mechanisms, food preserving and processing methods, and global market analysis of preserved foods. This review offers the researchers, technologists, and industry managements a comprehensive understanding that could be highly useful to develop effective and integrated food preservative methods and to ensure food safety.
Foods can be broadly classified according to the shelf life, functions and nutrient value, and processing mechanisms (Fig. 2). Different categories of foods are summarized in Table 1 and briefly discussed in the following sections.
Food spoilage is a natural process; through this process, food gradually loses its color, texture, flavor, nutritional qualities, and edibility. Consumption of spoiled food can lead to illness and in the extreme situation to death [9]. Considering the self life, food items can be classified as perishable, semi-perishable, and non-perishable [10].
Perishable Foods that have shelf life ranging from several days to about three weeks are known as perishable. Milk and dairy products, meats, poultry, eggs, and seafood are the examples of perishable food items. If special preservation techniques are not apprehended, food items could be spoiled straight away [10].
Semi-perishable Different food items can be preserved for long time (about six months) under proper storage conditions. These foods are known as semi-perishable. Vegetables, fruits, cheeses, and potatoes are few examples of semi-perishable food items.
Non-perishable Natural and processed foods that have indefinite shelf life are called non-perishable food items. These foods can be stored for several years or longer. Dry beans, nuts, flour, sugar, canned fruits, mayonnaise, and peanut butter are few examples of non-perishable foods.
Different food processing techniques are used by the food industries to turn fresh foods into food products. Foods can be classified into three major groups based on the extent and purpose of food processing [14]: (a) unprocessed or minimally processed foods, (b) processed culinary or food industry ingredients, and (c) ultra-processed food products. Classification of foods based on extent and purpose of processing is presented in Table 2.
Food spoilage is the process in which food edibility reduces. Food spoilage is related to food safety [9]. The primitive stage of food spoilage can be detected by color, smell, flavor, texture, or food. Different physical, microbial, or chemical actions can cause food spoilage. These mechanisms are not necessarily mutually exclusive since spoilage caused by one mechanism can stimulate another. Temperature, pH, air, nutrients, and presence of different chemicals are the major factors for food spoilage [9]. Different factors that affect food spoilage are presented in Fig. 3 and briefly discussed in the following sections.
Food spoilage due to physical changes or instability is defined as physical spoilage. Moisture loss or gain, moisture migration between different components, and physical separation of components or ingredients are the examples of physical spoilage [9, 15,16,17,18,19,20,21,22,23,24]. The key factors affecting physical spoilage are moisture content, temperature, glass transient temperature, crystal growth, and crystallization.
The effect of temperature is the most significant factor in the case of fruit and vegetable spoilage. There is an optimum temperature range for slow ripening and to maximize post-harvest life. Slow ripening also requires an optimum relative humidity along with optimum air movement around fruit and vegetable. Apparently, these optimum conditions are called modified atmospheres (MA). Temperature usually besets the metabolism of the commodities and contemporarily alters the rate of attaining desired MA [17]. Low temperature can also have a negative effect on foods that are susceptible to freeze damage. At a lower temperature, when food products become partially frozen, breakage in cells occurs which damages the product. Most tropical fruits and vegetables are sensitive to chilling injury. This generally occurs before the food product starts to freeze at a temperature in between 5 C and 15 C [9].
Glass transition temperature (T g) effects the shelf life of food products. Solids in food items may exist in a crystalline state or in an amorphous metastable state. This phenomenon depends on the composition of solids, temperature, and relative humidity [18]. The amorphous matrix may exist either as a very viscous glass or as a more liquid-like rubber [19]. At glass transition temperature, changes occur from the glassy state to rubbery state. This is a second-order phase transition process, which is temperature specific for each food. The physical stability of foods is related to the glass transition temperature. Glass transition temperature (T g) depends strongly on concentration of water and other plasticizers [22]. When dry food products are kept in highly humid conditions, the state of food products changes due to glass transition phenomena [9].
Freezing can also contribute to food degradation. Foods, which undergo slow freezing or multiple freeze, suffer severely due to crystal growth. They are subject to large extracellular ice growth. Rapid freezing forms ice within food cells, and these foods are more stable than slow freezing processed foods [23]. To minimize large ice crystal growth, emulsifiers and other water binding agents can be added during freezing cycles [20].
Foods with high sugar content can undergo sugar crystallization either by moisture accumulation or by increasing temperature. As a consequence, sugar comes to the surface from inside, and a gray or white appearance is noticed. Staling of sugar cookies, graininess in candies, and ice creams are the results of sugar crystallization [9]. Sugar crystallization can be delayed by the addition of fructose or starch. Moreover, above the respective glass transition temperature, time plays a crucial role in sugar crystallization process of food items [24].
Microbial spoilage is a common source of food spoilage, which occurs due to the action of microorganisms. It is also the most common cause of foodborne diseases. Perishable foods are often attacked by different microorganisms. The growth of most microorganisms can be prevented or lingered by adjusting storage temperature, reducing water activity, lowering pH, using preservatives, and using proper packaging [28].
Microorganisms involved in food spoilage can be divided into three major categories, which are molds, yeasts, and bacteria. Table 3 presents the active conditions of different microorganisms that affect foods.
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