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Fundamental knowledge of various unit operations of food processing which adds value and enhances the shelf life of the food products is very important for students and teachers. The main objective of this book is to present in a progressive and systematic form, the knowledge of fundamental food processing unit operations majorly required specially for undergraduate students. The applications of the unit operations in food processing and their explanations with numerical examples will help the students to understand the topic clearly. It will help the students to prepare for various competitive examinations also.

1. Introduction Law of conservation of mass says that material cannot be created nor destroyed, which is the basic fundamentals of physical science. Many engineering analyses involve material balances. These balances are simply accounting processes that account for all material in processes of interest. The material balance is one of the most useful tools fundamental in the “engineering approach” to design new process. The law of conservation of mass tells that the total mass of all material entering any process must equal the total mass of materials leaving plus the mass of any material accumulated in the process.

1. Introduction Energy balance means keeping an account of how the flow of energy is taking place in and out of any system or process. It helps the engineers to estimate the total energy requirement and identify the area for conservation of energy in any process. In food processing the concept of energy balance is applicable in unit operation such as blanching, drying, evaporation, freezing, refrigeration, distillation, crystallization. The scopes of energy balance in food industry are: i) Streamlining and reduction of energy consumption in the existing process. ii) Selection and sizing of any equipment and process. iii) Economic analysis of alternate process/technology. iv) Designing new economically viable process/technology

1. Introduction Movement of fluids from one location to another is an important unit operation in food processing. Various types of systems are used to convey fluids based on their flow behaviour. Understanding fluid flow behaviour is therefore important for designing of fluid flow systems. The fundamental mechanism involved in fluid flow is the momentum transfer occurring in moving fluids during various unit operations (fluid flow, aeration, drying, fluidization, filtration, centrifugation, sedimentation, mixing, etc.). This chapter deals with the basic concepts of fluid flow, viscosity, pressure measurement, conservation of mass and energy, boundary layer, momentum and velocity profile of fluid flowing in a pipe, flow metering devices, and pumps.

1. Introduction Thermal energy is transferred in the form heat from one body to another through conduction, convection and radiation or in combination of these modes. Some of the examples of heat transfer that occur during various agricultural processing is drying and dehydration, sterilization, pasteurization, evaporation, distillation, to name a few. The basic equation of conservation of heat can be written as: Rate of heat in + rate of heat generation= rate of heat out+ rate of accumulation of heat

1. Introduction Psyohrometrio is the study thermal and physical properties of gas-vapour mixtures. Ambient air is the mixture of dry air and water vapour and some pollutants. The moisture and pollutant content vary from place to place. The amount of pollutant and water vapour decrease with increase in the altitude. The air is completely dry above 10 km altitude. In many unit operations moist air is required and properties of air changes with temperature and pressure. The pollutants has to be removed before using moist air as a process air either by filtration or circulation. So it is necessary to determine the amount of water present in the air and effect of different unit operation on thermal properties and change in the heat and moisture content of mixture.The International Joint Committee of psychrometric data have fixed the composition of dry by mole fraction as: Oxygen: 0.2095, Nitrogen: 0.7803, Argon: 0.0093, Carbon dioxide: 0.0003. The following are the properties of the dry air Molecular weight    28.966

1. Introduction Thermodynamics is science of energy and may be defined as “The branch of science which deals with the Interoction between the heat and work is referred as Thermodynamics ’Thermo’ means heat and ’dynamics’ means motion. It deals with energy interaction when work is converted into heat energy or vice versa. Precisely, thermodynamics may be defined as a science which deals with energy transformation from one form to another and dealing with relationship among the properties ofthe system. In power plants, internal combustion engines, boilers, nozzles, diffusers etc. are the example where heat is converted into work. In compressor, turbine, cooling of engines by water, application of brakes in a vehicle etc. are the examples where work is converted into heat.

1. Introduction Refrigeration may be defined as the process of achieving and maintaining a temperature below that of the surroundings. The aim being to cool some product or space to the required temperature. Refrigerated system or a room system is maintained at a temperature which is lower than the atmospheric temperature. Due to higher temperature of atmosphere, heat enters the system. To keep the temperature of the system constant, heat must be removed continuously from the system. Heat removed must be equal to the heat transferred to the system. One of the most important applications of refrigeration has been the preservation of perishable food products by storing them at low temperatures. Refrigeration systems are also used extensively for providing thermal comfort to human beings by means of air conditioning.

1. Introduction Cleaning and grading are the first and vital post harvest operations undertaken to remove foreign and undesirable materials such as crop seed, chaff, mud, stones, straws, immature grains, dust, husk and even iron and steel particles from grains as well as fruits and vegetables and to separate the products into various fractions. Generally, the hand threshing and the traditional handling used in most developing countries cause a larger percentage of foreign matter with these crops. Thus, more cleaning is required. Cleaning is essentially a separation process, in which some difference in physical properties of the contaminants and the food units is exploited. 

1. Introduction Size reduction is applied to all the ways in which particles of the solids are cut or broken into smaller pieces. Size reduction operation of solids is referred to as 'Comminution", some of the common comminutive processes are - crushing, grinding, milling, mincing, and dicing. Breaking down of large sized particles of food substances into smaller particles is a common unit operation in many food processes, e.g. wheat flour, turmeric powder, spices, etc. are mostly used in powdered form. Some ofthe common objectives that are fulfilled by size reduction are:

1. Introduction Raw milk is an emulsion. It is a mixture of milkfat globules, Solid Not Fat (SNF) and water. Over time, milkfat globule separate out from milk serum and comes to the surface of milk as a layer of cream due to the low density of milkfat or due to heating of milk. When milk is heated rapidly and continuously, some of the water in it evaporates from the surface. This exposes proteins and fat molecules, which bind and dry out and forms a skin like film on the surface. 

1. Introduction Mixing is a fundamental and widely practiced operation in many fields, such as chemical, pharmaceutical, and food processing industries. The mixture’s primary aim is to increase the homogeneity of the material in bulk (Uhl and Gray, 1986; Patterson et al., 2004). Mixing means the random distribution of two or more ingredients throughout a system, which differs from the term’ agitation,’ which is defined as establishing a particular flow pattern with the liquid, especially in a circulatory motion within a container. Mixing is a necessary step in the context of food processing operations. 

1. Introduction Freezing is a method of food preservation that involves lowering the temperature below the freezing point of food generally -18 °C or below. During freezing of food the water present in them changes its state to form ice crystals. Human beings in the colder regions have used freezing as a means of preservation since they learnt hunting and gathering foods. The foundation of the modern frozen industry was laid in mid 1920 when Clarence Frank Birdseye, an American inventor used cold brine solution to chill packaged fish and extended it further for quick freezing of meat poultry fruit and vegetables. 

1. Introduction Milk is a source of abundant nutrition has been a vital part of human civilization since prehistoric times. However, because of its perishable nature, it requires immediate processing to improve the shelf life and safe consumption .With the advancement of processing techniques in dairy and food processing, there is a widespread option being utilized to improve the milk shelf life byeither thermal technologies (pasteurization, sterilization, and ultra-high temperature) or nonthermal technologies (high pressure processing, high pressure homogenization, pulse electric field and ultra sonication). Still, pasteurization and sterilization are the two foremost process is used for milk industries. Pasteurization is the thermal inactivation of microorganisms at temperatures below100°C that enhance the safety and quality of milk and milk products and extends the shelf life to an extent. 

1. Introduction To maintain good quality of product & shelf life, it is very important & essential to concentrate on Cleaning & Sanitization process at plant level & to follow the CIP process properly. An attempt is made in the current chapter to present details pertaining to cleaning in fluid milk and milk products manufacturing & processing plants. This chapter will be helpful the students of Food & Dairy Technology for better understanding the process milk plant cleaning & sanitation technology.

1. Introduction Foods available in nature and, in some cases, the products made from it thereof contain quite an amount of water. This water not only adds volume to the food products but also provides a sight for attack by the micro organisms. Also, removal of water becomes essential if this water interferes with the end product chracteristics. There are several processes in food industries which are designed to get rid of this excess water, such processes are called concentration processes. The processes which can remove water from food substances are,- evaporation, freeze concentration and membrane based processes. All these process have their limitations in rendering solid content to the final product (Fig. 1). Perhaps, these limitations can be overcome by combinig the processes. The objectives that are fulfilled by the concentration processes can be enumerated as follows:

1. Introduction Drying is a thermo physical and physicochemical process, which involves removal of excess water from a solid, semi-solid or liquid food material by evaporating it into vapour phase on applying heat, to reduce growth of microorganism or to completely eliminate their growth. Hence, reducing the water activity increases shelf life of food products. Drying medium for carrying evaporated moisture can be air or steam. Benefits of drying include increase in shelf life, easy to transport, handle food material and reduce packaging cost as it reduces bulk weight. 

1. Introduction Membranes separation processes have gained widespread applications in food industry. High selectivity of membrane has been exploited for separating a particular component from complex liquid food mixture and for controlled release of active ingredients like preservatives or flavor compounds. Today, a number of chemical processes utilizing the unique properties of membrane have been developed for commercial application in food industry with specific advantage of low energy requirement. Membrane separation/molecular sieving is one among those food engineering principals which has found broad range of applications including concentration of heat labile compounds, recovery of solvent, downstream processing, flavor volatile recovery, deacidification, desalination, waste water treatment etc

1. Introduction Extrusion of foods is an emerging technology for the food industries to process and market a large number of products of varying size, shape, texture and taste. Extrusion cooking of cereals is becoming more adaptive due to its various advantages over the traditional food processing techniques (White, 1994). Nowadays the extrusion of food is of major importance in the food-processing sector and it is the only process, which covers a wide range of food products such as ready to eat (RTE) breakfast cereals, snack foods, baby foods etc. Elaborate scientific research, technological development and engineering design, which have been done in this field so far, have led to large-scale industrial production. 

1. Introduction Thermal processing used extensively in the food industry for preservation and shelf life extension of the products (Arnoldi 2001). Heat treatments remain most important in food processing unit operations, not only to achieve desirable changes in eating quality but also for preservative effect by inactivation of microorganisms, destruction of enzymes and insects.Heat is applied in various unit operations through adifferent mode of heat transfer such as conduction, convection, and radiations. 

1. Introduction Heat transfer from a hot surface is a general method or technique of heating liquids and slurry type of food materials. In such cases the heat can be generated either directly by a heating element or indirectly from a hot medium like steam or hot water via a heat exchanger (e.g. shell and tube, plate). Therefore, for the heat transfer during heating by these techniques a temperature gradient will be required, which usually causes the fouling on the surface of the heating element or heat exchanger. Afterwards the fouling not only reduces the heat transfer rate but also results in quality deterioration within the product which is being processed. 

1. Introduction Thermal processing treatments are the conventional methods that have been broadly employed in the food industry to guarantee the microbiological safety of food materials at a minimal cost. However, these thermal treatments cause undesirable changes in flavor, nutritive value, texture, or color of the finished product that impact food quality (Pan et al., 2017). Growing the modern consumer’s demand towards the minimally processed and “fresh-like” taste foods has challenged the food industry to develop novel non-thermal preservation techniques as an alternative to thermal processing. 

1. Introduction In recent years, consumers have been demanding convenient, healthy and safe foods which have ’fresh-like’ characteristics with a long shelf-life. These demands include important food quality such as appearance, texture, taste and nutritional content which are strongly impacted by the way it is processed. Another major concern among the consumers is food safety and quality. The shelf-life of the food products are mostly influenced due to the action of various harmful microorganisms and enzymes. The conventional food processing technologies, such as thermal treatments (pasteurisation and high temperature sterilisation), evaporation, drying, frying and baking can assure the microbiological safety and/or stability of processed food products, but affects the food quality and nutrients (heat sensitive vitamins, flavour and other bioactive compounds) (Zhang et al., 2019)

1. Introduction Packaging is the integral part and cornerstone of food processing industry. The development of food processing industry goes hand in hand with advancement of packaging technology. Packaging Institute International has defined packaging as “enclosure of products, items or packages in a wrapped pouch, bag, box, cup, tray, can, tube, bottle or other container form to perform one or more of the following functions: containment, protection, preservation, communication, utility and performance”. Lockhart has defined packaging as “a socio-scientific discipline that operates in society to ensure the delivery of goods to the ultimate consumer of those goods in the best condition intended for their use”. Food packaging technology has came a long way from use of anything in hand for wrapping up a product to becoming a key element in product development and design.

Symbols 12-D Process 238 A Abrasion peeling 161 Absolute humidity 295 Absolute Humidity/Humidity Ratio/ Specific Humidit 92 Acids 260 Active Packaging 451 Adiabatic humidification 103