Preface This textbook has been written for the students of B.Tech. (Dairy Technology) course being offered by different Dairy Science Colleges and various Agricultural and Deemed Universities across the country. Though several books are already available on this subject, they are too comprehensive to be preferred by B.Tech. students. Here, this is an attempt to cover all the topics related to the course ‘Biochemistry and Human Nutrition’, which is written strictly based upon the course curriculum prescribed by Indian Council of Agricultural Research (ICAR), New Delhi for B.Tech. students. This book will also be helpful for those students, who study biochemistry and/or human nutrition as one of the subjects in Food Technology, Food Science and Technology, Food and Nutrition and other allied streams of under-graduate levels. This book is mainly divided into two sections: 1) Biochemistry; 2) Human Nutrition. First section comprises eight chapters based on metabolism of macronutrients (carbohydrates, proteins and lipids), basics of vitamins, enzymes, hormones and nucleic acids. Second section deals with the digestion & absorption of macronutrients, nutritional requirements of different age groups, analytical methods for qualitative & quantitative determination of nutrients, milk intolerance & hypersensitivity, safety aspects of food additives, toxic elements and radionuclides and various nutritional polices initiated by Government of India to combat malnutrition.

Introduction Billions of chemical reactions are happening inside human body and that too with lightning speed. However, the same reactions if carried out in laboratory, they take a very long time. The reasons behind it are the biocatalysts, also known as enzymes, which are synthesized by living cells. Chemically, they are proteins(except ribonucleic acids: RNA), colloidal in nature, thermo-labile in character and very specific in their action. For example, hydrolysis of proteins by a strong acid at 100°C takes a couple of days; but same proteins can be digested within couple of hours inside human body at 37°C. Similarly, carbonic anhydrase is used as a catalyst by living cells to transfer carbon-di-oxide from cells to blood. This process is 107 times quicker than the same process if occurs without the help of enzymes. Therefore, enzymes can be defined as the biomolecules or biocatalysts which can speed up the rate of the chemical reactions. The substance upon which an enzyme acts is called as substrate and the one which is produced as the result of enzyme-substrate reaction is known as product.

Introduction The nucleic acids are the molecular depots that are responsible for continuity of life by transfer of hereditary information from one generation to next. The sequence of nitrogenous bases containing programmed instruction determines the structure of every cell constituent and eventually every protein. In 1869, Friedrich Miescher, Swiss chemist, isolated an unknown phosphate-rich substance from pus cells named as nuclein, which was quite different from other organic substances like carbohydrate, protein, and fat. Altmann in 1899 ascertained that the nuclein also had some acidic characteristics and changed its name to ‘nucleic acid’. Later, nucleic acid was also isolated from salmon sperm nuclei as DNA-protaminecomplex. In 1953, James D.Watson and Francis H.C. Crick constructed the model of three-dimensional double helix structure of the DNA molecule which could successfully explain DNA replication.

Introduction The basic components of diet include carbohydrate, protein, fat, vitamins and minerals. Vitamins are the essential nutrients which are not formed in our body and required in minute amount from the diet. Vitamins are crucial for the optimal functions of several enzymes; thus important for optimal growth and development. Vitamins perform various functions that help in regulation of metabolism, prevent chronic diseases, maintain natural appetite, mental health and immunity. In 1912, Polish biochemist Kazimierz Funk coined the term ‘vitamine’;a substance that was present in rice polishing and foods that cured polyneuritis in birds and beriberi in humans. The name is from ‘vit’ for vital nutrient and ‘amine’ for its similarity as an amine. Vital signify that these factors are indispensable for life. Earlier they are identified and thought to contain amino groups, thus the word amine was used, which was true for thiamine but later work revealed that most of the vitamins do not have amino groups. Thus the word was shortened to vitamin in English. It should be noted that the term vitamin does not denote to some othern utrients such as essential amino acids, essential fatty acids, dietary minerals or other nutrients that contribute towards good health. Vitamins may be defined as organic compound needed in minute amount through diet to perform specific biological functions for normal growth and health of the organisms.Vitamins should have following characteristics:

Introduction Hormones may be defined as specific chemical molecules produced in certain specific organs called specialized cells or endocrine glands. They are delivered into the blood stream or some other body fluid in minute amounts by the circulatory system of the body and their they exerts a physiological effect at a site of action remote from its origin, regulating numerous biological activities including growth, development, reproduction, water & electrolyte balance, storage & usage of energy etc.

Introduction Carbohydrates are the most common source of energy for all living cells, which, in presence of light, are formed by the green plants from CO2 and water during photosynthesis. It canbe said that ‘light’ is theultimatesourceof energyrequired for all livingcells.Glucose,a monosaccharide,plays a centralroleincarbohydrate metabolismin all plants, animals and manymicroorganisms. Glucose is derived from the polysaccharides (starch, glycogen) and non-carbohydrate sources (amino acids, glycerols, etc.) during metabolism and ultimately converted either into carbondioxide and water orotherintermediateproducts.Complete oxidation of glucose to CO2 and water provides ~2,840 kJ/mol energy. The other monosaccharides such as fructose, galactose, mannose, etc. are also important molecules in carbohydrate metabolism.

Introduction The diverse cluster of naturally occurring organic compounds including fats, oils, fatty acids, waxes, phospholipids, eicosanoids, terpenes, steroids and fat soluble vitamins that do not prefer to interact with water but soluble in non-polar organic solvents like ether, chloroform, benzene, acetone, are called as lipids. The main functions of lipids in biological system include storage and transport of metabolic fuel, structural component of cell membranes, insulation & protection of vital organs from shock and carrier of fat soluble vitamins. Contradictory to proteins,lipids are not polymers in nature and are hydrophobic due to presence of a long hydrophobic chain. Apart from this, lipids also act as precursor molecules for several pigments, hormones and signaling molecules.

Introduction Proteins are the most abundant organic compounds constituting major part of the body. Chemically, proteins are nitrogen containing macromolecules and polymers of L α-amino acids, which serve a wide range of structural and biological functions in animal body. For example, connective tissue made up of collagen, metabolicenzymes, neuro transmitters,signal in gmolecules, structural components of cell membranes and cell organelles, etc. all are chemically proteins. Before goinginto the details of protein metabolism, first, we need to understand that there are majorly two sources of proteins in our body: dietary protein and body protein. Dietary protein is taken in diet, while body protein indicates the protein and amino acids synthesized in animal body to fulfill the requirements for growth and development. The digestion of proteins will not be discussed here as it has been described in detail in chapter 12. Dietary protein is digested in presence of several enzymes such as trypsin, pepsin, chymotrypsin, aminopeptidases and carboxypeptidases and is converted into mono-, di- and oligopeptides in stomach and small intestine; and finally converted into amino acids. These amino acids are transported to the systemthrough intestinal mucosa via active transport, from where they enter into the cells for further metabolism. Therefore, ‘metabolismof proteins’ is more appropriatelylearnt as ‘metabolism of amino acids’.

Introduction The basic physiological structures of mammary glands in all species are almost same and are located externally in order to fulfill the milk requirement of neonates after parturition. The process of secretion of milk from the mammary glands is known as lacto genesis. Milk provides an almost complete nutrition to neonates from birth till weaning period. It is a complex mixture of various constituents like: Lipids such a striacyl glycerols(TAG),phospholipids,cholesterols and other sterols, free fatty acids and fat-soluble vitamins Carbohydrates such as lactose, oligosaccharides Proteins such a scaseins, α-lactalbumin, β-lactoglobulin, immunoglobulin’s, bovine serum albumin, lactoferrin, lysozyme, enzymes, hormones and growth factors Non-protein nitrogenous compounds like urea, creatine, creatinine, uric acid and amino acids Major and minor minerals, water-soluble vitamins and cells (leucocytes, macrophages, and epithelial cells).

Introduction Nutrition, a basic human need, is a critical part of health and development. Nutrition can be defined as the intake of food, deliberated in relation to the body’s dietary needs. On one hand, good nutrition – an adequate, well balanced diet combined with regular physical activity – is a foundation of good health, whereas,poor nutritionleads toreducedproductivity,impairedmental andphysical development, increased susceptibility to disease, and reducedimmunity. According to WHO, under-nutrition, together with vitamin and mineral deficiencies accounts for one-third of all child deaths and impairs healthy development and lifelong productivity. At the same time, sedentary lifestyles, demographic shifts, urbanization and the liberalization of markets have steered the world population to being overweight along with risk of chronic diseases like hypertension, dyslipidemia, type 2 diabetes, coronaryheart disease, stroke, etc.; thus, resulting in a double burden of malnutrition. To address this dual burden of malnutrition, individuals needaccess to sufficient and good quality food; but focussing solely on food security is unlikely to solve the problem of global malnutrition. The challenges of malnutrition cannot be solvedjustbyincreasingfoodproductioninordertoimprove healthand nutritional status of the population. To resolve such challenges, awareness about food choices for optimal health plays a pivotal role among population. Human nutrition is the science of understanding food; its component; intake; and how it is related to health, growth, development and diseases. Human nutrition involves the study of ingestion, digestion, absorption and assimilation of the nutrients; their metabolic functions, deficiency or excess disease as well as their regulation through several factors such as choosing particular food components/nutraceuticals or physical activity.

Introduction Nutrition is the fundamental pillar of life and an essential foundation of human and national development. Rightfrom the earliest stage of human development, the fetal stage, at birth, infancy, childhood, adolescence, adulthood and old age, nutrition forms the basis for survival, performance, mental and physical development & economic and social development.Nutritional deficiencies during pregnancy, fetal and early postnatal life can have a negative impact not only on the subsequent growth and development but can also lead to changes in metabolic regulation and homeostasis.

Introduction Nutritive value of any food indicates the calories content as well as quality attributes. Macronutrients such as carbohydrates, fats and proteins provide energy by4-9-4 rule. It meanstheyprovide 4,9 and 4 kcal/genergy, respectively, when oxidized completely. Though micronutrientssuch as vitaminsandminerals do not provide any calories, they are essential for the enzymatic activity and metabolic reactions. ATP or energy is measured in terms of ‘calories’ or ‘joule’. One calorie is the amount of heat required by 1g of water to increase its temperature from 14.5 to 15.5°C under standard conditions. Nutritive value of any food can be measured on shelf usingcalorimeter, in which food is completelyoxidized under specified conditions and converted into CO2 and water.

Introduction Digestion may be defined as the hydrolytic process carried out by various enzymes for breaking down complex food components such as proteins, fats and carbohydrates into simpler molecules like amino acids, fatty acids and monosaccharides, respectively. Whereas, absorption may be defined as the movement ofthese simple soluble digested food componentsalongwithvitamins, minerals and water from gastrointestinal track into the circulatory system. The process of digestion starts from oral cavity (mouth) and ends at large intestineincluding tongue, teeth, jaws,secretions from salivaryglands (parotids, sub maxillary or submandibular and sublingual glands), pharynx, esophagus, stomach, small intestine and digestive enzymes secreted from pancreas and liver.

Introduction There are manypeople all over the world who have a certain level of sensitivity or intolerance towards milk and milk products. The reactions to milk which involve the immune systemare termed as milkallergy, whereas, difficulty in the digestion of the milk and milk products is known as milk intolerance. Milk intolerance occurs due to malabsorption of milk sugar (lactose) in intestine, a condition in which lactose is not digested into its monomers (galactose and glucose) due to lower activity or insufficiency of lactase enzyme. Inability to digest lactose, which is a disaccharide present only in milk, is specifically known as lactose intolerance. However, hypersensitivity involves the adverse immune reaction(allergic reaction) inthe body causeddue to the ingestion of milk proteins. Milk and milk products are major source of basic as well as essential nutrients and cannot be skipped from the diet of the individual. It is a rich source of calcium,which is essential for the growth and reformationof bones. The decline in calcium may lead to thin, fragile bones that break easily, a condition called osteomalacia or osteoporosis in women. Thus, it is a matter of concern for both children andadults whoare allergic or intolerant towards milk and milk products and not getting enough calcium and other nutrients in diet. This chapter would provide more insight about milk intolerance and milk allergy/hypersensitivity and how to deal with it.

Introduction Spectacular accomplishment in every sector has enabled India to be amongtop achieving nations. However, every section of the society is not benefited by these achievements and problem of malnutrition still remains unresolved. Malnutrition is a common problem faced by underdeveloped and developing countries suchas Philippines, Nepal, Sudan,Tanzaniaand Indiasincelongback. Malnutrition includes undernutrition(wasting,stunting,underweight),inadequate vitamins or minerals as well as overweight, obesity and resulting diet-related non communicable diseases(NCDs). As per the latest report of World Health Organization, 52 million children under 5 years of ageare wasted, 17 million are severely wasted and 155 million are stunted, while 41 million are overweight or obese (WHO, 2018). More than 50% women of marriage age are suffering from anemia. If women are malnourished at the time of pregnancyand delivery, the babybornface theproblems such asphysical retardation,sensitive tocommon infections, reduced cognitive abilities, reducedmental development, etc. As per the World Health Organization (WHO) guidelines, starting from the date of conceiving a child, the first 1000 days are a critical window from nutrition point ofview.Unfortunately, inseveral regions of developingcountries includingIndia, neither the mother nor the babyis provided with the right quantity and qualityof food during this window period. Therefore, it is important for the policymakers to identifymalnutrition at an earlystage for timelyplanningand implementation of various intervention strategies at the community, village, and district level. NitiAyog, Government of India (GoI) (previously known as Planning Commission), in an effort to eliminate malnutrition,regularlyplans several short and longtermnutritionalprogrammesand policies.In thischapter,we willdiscuss some of these policies launched since independence and their impact in combatingmalnutrition.

Introduction The dairy sector is one of the most important food sectors, which introduced the physical, chemical, microbiological and sensorial criteria duringprocessing steps and in the final dairy products. Several agents/ingredients of non-dairy origin are commonly used to maintain the quality of milk and milk products during processing, transportation and storage. In general, such ingredients are known as food additives and it can be antioxidants, coloring agents, flavoring compounds, preservatives(naturals and synthetic),artificialsweeteners, vitamins, minerals, stabilizers, emulsifiers and curing agents. From the safety point of view, some toxic agents can come into contact of dairy products duringmilking, storage or processing; such as fungal toxins, heavy metals, antibiotics or radionuclide’s, etc., which need to be identified and processed accordingly. Although addition of food additives in food/dairy product is controlled under country specific food laws or Codex Alimentarius Commission (CAC), few dairyproducts such as butter and unflavored fermented milk products are highly restricted for food additives.