eChapters

Thermal preservation is among the most established methods for improving the safety and storage life of food. It uses controlled heating to destroy spoilage organisms and pathogens and to inactivate undesirable enzymes. Processing intensity varies according to the target microorganisms, food composition, packaging and required shelf life. Pasteurisation reduces pathogenic and spoilage microorganisms without achieving complete sterility, while sterilisation destroys more heat-resistant organisms and spores to produce commercially stable foods. Ultra-high-temperature processing combines very high temperatures with extremely short treatment periods. This chapter also discusses retort processing, thermal-death kinetics and microbial-inactivation models used to design safe processes while minimising nutritional and sensory damage.

Introduction
Heat treatment is the most commonly used method in the dairy industry for milk processing. Its primary objective is to eliminate pathogens and reduce spoilage-causing organisms, ensuring milk is safe for consumption and has a longer shelf life. While advanced methods like high-pressure processing, pulsed electric fields, ultrasound processing, cold plasma treatment, and ultraviolet sterilization have emerged, heat treatment remains the preferred choice due to its simplicity, reliability, and proven effectiveness. All dairy products undergo some form of heating during processing, whether through pasteurization, sub-pasteurization (e.g., for milk used in aged cheeses), or sterilization. To facilitate this, liquid heating systems such as continuous heat exchangers or jacketed tanks are widely used, typically powered by steam or steam-heated water. Consequently, steam generation boilers are a standard feature in almost all dairy processing facilities.
The Key Objectives of Heat Treatment Include
1. Elimination of harmful pathogens in milk, ensuring it is safe for consumption and protecting public health.
2. Increasing the keeping quality of milk by reducing the number of spoilage organisms.
3. Inactivating enzymes naturally present in milk or secreted by microorganisms to prevent enzymatic degradation.
4. Preventing the autoxidation of lipids, which can lead to off-flavors and spoilage.
5. Inactivating agglutinin to reduce rapid creaming and maintain uniform consistency.
6. Enhancing the growth of starter cultures by eliminating natural inhibitors and dissolved oxygen in milk, essential for producing cheese and fermented products.

Thermal processing also known as heat processing is commonly used processing method which helps in extending the shelf life of the food productswith high safety level, convenience and a healthy product.Seafood as a whole food is highly nutritious. Benefits to human health associated with the consumption of seafood is well recognized for multiple bodily organs and physiological functions but their high perishable nature is a concern. Seafoodundergoes spoilage due to autolytic, microbial action as well as oxidation of lipid. Proper handling and preservation is essential to maintain quality of fish. Heat processing is an age old preservation method practiced in many countries to extend the shelf life of food products. Heat treatment causes the destruction of microbes which increases the shelf life. There are number of thermal processing operations like- baking, blanching, canning, dehydration, extrusion, frying, pasteurization, sterilization, etc. All these operation serves various purposes and helps in manufacture of different food products.

Thermal processing is of utmost importance to low acid high water activity foods, where there are no hindrances to microbial growth. The proper delivery of heat is essential to cause the destruction of microbes to avoid food spoilage. In seafood’s processing, thermal processing through canning (retort pouch processing) is a common approach. In canning, the food is preserved by application of heat in hermetically sealed cans (pouches). Hermetic sealing means- complete airtight sealing. This prevents contamination from outside. Heating at very high temperature ranging from 110 to 135⁰C for a desirable time helps in killing all the vegetative forms of microorganisms as well as most heat resistant microbial spores. The amount of time needed for processing is different for each food type depends on hurdles present in the food and heat transfer characteristics. In thermal processing of seafood products, heat processing is aimed for the destruction of spores of Clostridium botulinum. A number of thermally processed ready-to-eat (RTE) products are available on market shelf.

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.

1. INTRODUCTION

Thermal processing means preservation by application of heat. It involves heating of foods in hermetically sealed containers for a specific time at a specific temperature to eliminate the microbial pathogens that endanger public health and that micro-organisms that deteriorate food during storage. The credit for invention of thermal processing (Canning) goes to a French Confectioner, Nichola Appert. The application of heat is an important method of preserving foods and is also a means of developing texture, flavour and colour in some foods.

Q. 1 The amount of heat required to raise the temperature of 1gm milk by
one degree celsius in comparison to water is
(A) 85 %     (B) 93 %
(C) 107 %    (D) 100 %

4.1 Introduction

The food preservation may be define as the state in which the food may retained over a period of time without being contaminated by pathogenic organism or chemicals and without losing its colour, texture, flavour and nutritional value. All the methods of food preservation must provide such an environment in and around the preserved food so that it produces one or more unfavourable conditions to the continued activity of the spoilage agents. The various methods used for food preservations are:

Abstract

Thermal properties of food are its ability to conduct, store and lose heat. These properties are inherent in food processing and preservation practices. Thermal properties are important for modelling processes, engineering design of processing equipment, sterilization and aseptic processing. Important thermal properties are thermal conductivity, specific heat and thermal diffusivity. These properties depend on chemical composition, water fraction and temperature.

Introduction

Thermal properties are involved in almost every food processing operation. It is essential to have knowledge of thermal properties of foods which is important in analysis and design of various food processes and food process equipment involved in heat transport. Thermal properties of food are greatly depending on composition, temperature and density of food. Thermal properties required for heat transfer calculation include specific heat, enthalpy, thermal conductivity and thermal diffusivity. Thermal properties of foods are related to heat transfer control in specified foods and can be classified as thermodynamic properties (enthalpy and entropy) and heat transport properties (thermal conductivity and thermal diffusivity). Thermo physical properties not only include thermodynamic and heat transport properties, but also other physical properties involved in the transfer of heat, such as freeze and boiling point, mass, density, porosity, and viscosity. These properties play an important role in the design and prediction of heat transfer operations during the handling, processing, canning, storing, and distribution of foods.

Temperature stands as a fundamental environmental factor profoundly influencing the life cycle of crops, from the initial spark of germination to the final stages of maturation and yield formation. The thermal regime, encompassing the daily and seasonal patterns of temperature, dictates the rate of biochemical reactions within the plant, thereby governing the pace and efficiency of physiological processes crucial for growth and development.
This chapter, „Thermal Regime: Crop Growth and Development,“ will delve into the intricate relationship between temperature and the various phenological stages of crop plants. It will be explored how different cardinal temperatures – the minimum, optimum, and maximum thresholds – dictate the boundaries within which growth can occur and the rates at which developmental milestones are achieved. Understanding the impact of temperature on processes like photosynthesis, respiration, nutrient uptake, and ultimately, yield, is paramount for optimizing crop production in diverse environments.
Furthermore, we will examine the concepts of heat units or growing degree days, which provide a quantitative framework for predicting crop
development based on temperature accumulation. By appreciating how the thermal environment interacts with genetic potential and other environmental factors, we can gain valuable insights into crop suitability for specific regions, the timing of critical growth stages, and strategies for mitigating the adverse effects of temperature extremes.
This chapter aims to provide a comprehensive understanding of the thermal regime and its critical role in shaping the growth and development of our cultivated plants, laying the foundation for informed agricultural practices and improved crop management.

Temperature stands as a fundamental environmental factor profoundly influencing the life cycle of crops, from the initial spark of germination to the final stages of maturation and yield formation. The thermal regime, encompassing the daily and seasonal patterns of temperature, dictates the rate of biochemical reactions within the plant, thereby governing the pace and efficiency of physiological processes crucial for growth and development.
This chapter, „Thermal Regime: Crop Growth and Development,“ will delve into the intricate relationship between temperature and the various phenological stages of crop plants. It will be explored how different cardinal temperatures – the minimum, optimum, and maximum thresholds – dictate the boundaries within which growth can occur and the rates at which developmental milestones are achieved. Understanding the impact of temperature on processes like photosynthesis, respiration, nutrient uptake, and ultimately, yield, is paramount
for optimizing crop production in diverse environments.
Furthermore, we will examine the concepts of heat units or growing degree days, which provide a quantitative framework for predicting crop
development based on temperature accumulation. By appreciating how the thermal environment interacts with genetic potential and other environmental factors, we can gain valuable insights into crop suitability for specific regions, the timing of critical growth stages, and strategies for mitigating the adverse effects of temperature extremes.

Thermal stress arises whenever there is some increase or decrease in temperature of a body which causes either expansion or contraction in the dimension of body. If body is free to expand or contract, with the rise or fall of temperature, there exist no stress in the body. But if deformation of the body is partially or completely resisted then stresses are set up in the body which is known as Thermal Stress. However amount of stress induced in partially prevented deformation will be small than in case deformation is totally prevented.

Polymerase Chain Reaction

The Polymerase Chain Reaction (PCR) technique, invented in 1985 by Kary B. Mullis, allowed scientists to make millions of copies of a scarce sample of DNA. The technique has revolutionized many aspects of current research, including the diagnosis of genetic defects and the detection of the AIDS virus in human cells. The technique is also used by criminologists to link specific persons to samples of blood or hair via DNA comparison. PCR also affected evolutionary studies because large quantities of DNA can be manufactured from fossils containing but trace amounts.

Kary Mullis invented the PCR technique in 1985 while working as a chemist at the Cetus Corporation, a biotechnology firm in Emeryville, California. The procedure requires placing a small amount of the DNA containing the desired gene into a test tube. A large batch of loose nucleotides, which link into exact copies of the original gene, is also added to the tube. A pair of synthesized short DNA segments, that match segments on each side of the desired gene, is added. These “primers” find the right portion of the DNA, and serve as starting points for DNA copying. When the enzyme Thermus aquaticus (Taq) is added, the loose nucleotides lock into a DNA sequence dictated by the sequence of that target gene located between the two primers.

The test tube is heated, and the DNA’s double helix separates into two strands. The DNA sequence of each strand of the helix is thus exposed and as the temperature is lowered the primers automatically bind to their complementary portions of the DNA sample. At the same time, the enzyme links the loose nucleotides to the primer and to each of the separated DNA strands in the appropriate sequence. The complete reaction, which takes approximately five minutes, results in two double helices containing the desired portion of the original. The heating and cooling is repeated, doubling the number of DNA copies. After thirty to forty cycles are completed a single copy of a piece of DNA can be multiplied to hundreds of millions.

2.1 Introduction

The name thermodynamics stems from the Greek words therme (heat) and dynamis (power), which is most descriptive of the early efforts to convert heat into power. It may be defined as the science that deals with the relations among heat, work and properties of a system. Today, thermodynamics is broadly interpreted to include all aspects of energy and energy transformations, including power generation, refrigeration, and relationships among the properties of matter. It is viewed as the science of energy, and thermal engineering is concerned with making the best use of available energy resources.

Thermodynamics basically entails four laws or axioms known as Zeroth, First, Second and Third law of thermodynamics.

The zeroth law deals with thermal equilibrium and establishes a concept of temperature.

The first law pertains to the conservation of energy and introduces the concept of internal energy.

The second law indicates the limit of converting heat into work and introduces the concept of entropy.

The third law defines the absolute zero of entropy.

The concept of energy was introduced by Newton in the field of mechanics during generalizing the hypothesis of kinetic and potential energies. Energy may be defined as the capacity to do work and it is a scalar quantity. It cannot be seen or observed. Its presence can, however, be felt by the properties of the system. There occurs a change in one or more properties of the system in case of energy transfer. The absolute value of energy of a system is difficult to measure, whereas the energy change is rather easy to calculate. Energy follows the conservation law, one of the most fundamental laws of nature, which simply states that during an interaction, energy can change its form from one form to another but the total amount of energy remains constant, that is, energy cannot be created or destroyed only form can be changed.

Direction of rotation can be reversed in
(A) 2- stroke engine           (B) 4- stroke engine
(C) Both (A) and (B)          (D) None of these

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.

Thermodynamics is defined as the “branch of science which deals with the interaction between the heat and work”[1]. Thermodynamics is also sometimes stated as the science of energy. Thermodynamic deals with the principles of energy and energy conversion in engineering. It also considers the thermodynamic properties of substances. Thermodynamics deals with the conversion of heat into work and vice-versa.

Based on the nature and purpose of the content, there are numerous classes of scientific communications. Theses represent the class of research communications that are of great importance to the students. Thesis is part and parcel of the master’s and doctoral programme in almost every academic institution. In some institutions, even the bachelor students are expected to submit their brief report on project.

Chromatography is an important analytical technique for the separation, isolation and identification of the constituents of a mixture. It is a physical method of separation in which the components to be separated are distributed between two phases; one of these phases consisting a stationary bed of large surface area, the other being a fluid that percolates through or along the stationary bed. All forms of chromatography do have the common features given in this definition. All of them involve the physical movements of the sample across a flat surface (tube like) or through a tube. The stationary phases in all of these possess a large surface area. In all the techniques, the movement of the sample is due to the motion of the fluid/mobile phase. The principle underlying all these methods is the selective retardation of the movement of the components by the stationary phase. These methods result in the production of bands of concentrated components. The basis of naming various chromatographic methods are different: