Introduction to Food Science PDF

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Chapter 1 Introduction to Food Science Allah Rakha, Masood Sadiq Butt and Muhammad Asif Khan* Abstract This chapter is a prelude to the book and provides an overview to the readers about food, its constituents (carbohydrates, protein, lipids, vitamins and minerals), and a brief classification based ...

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Chapter 1

Introduction to Food Science Allah Rakha, Masood Sadiq Butt and Muhammad Asif Khan*

Abstract This chapter is a prelude to the book and provides an overview to the readers about food, its constituents (carbohydrates, protein, lipids, vitamins and minerals), and a brief classification based on their functions as a core component. The chapter provides a breif information about food and their behavior towards processing technology with an overview of food composition, sources and significance of food to the human health to highlight perspective of fundamentals of food science and technology. Keywords: Food, Nutrients, Food Science, Food Technology, Processing, Spoilage

1.1.

Food

Food may be defined as “anything eaten or drunk that meets the need for energy, body building, regulation and protection of the body” (Somati et al. 2007) to sustain life. Food includes any solid or liquid which on swallowing can supply one or more of the following: •

Materials from which body can produce movement, heat, or other forms of energy

•

Materials for growth, repair, regeneration and reproduction

•

Substances necessary to regulate processes of growth & maintenance.

Thus, food may be considered as a fuel that supplies energy to the body to support our daily activities and synthesize necessary materials within the body revealing

* Allah Rakha, Masood Sadiq Butt and Muhammad Asif Khan˧ National Institute of Food Science and Technology, University of Agriculture, Faisalabad, Pakistan. ˧ Corresponding author’s e-mail: [email protected]

Managing editors: Iqrar Ahmad Khan and Muhammad Farooq Editors: Tahir Zahoor and Masood Sadiq Butt University of Agriculture, Faisalabad, Pakistan.

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A. Rakha, M.S. Butt and M.A. Khan

direct effect on human body and its functionality. Consequently, food composition / constituents are considered as the major determinant of human health and wellbeing. Food has been classified into numerous groups based on consumption pattern. The one such classification categorizes them into basic four (cereals, millets, pulses; milk, milk products and animal foods; vegetables and fruits; oils, fats, nuts and oilsseeds) basic five (fats and sugars; cereals, grains and products; fruits and vegetables; pulses and legumes; milk and meat products) and basic seven (butter or fortified margarine; green and yellow vegetables; bread flour and cereals; meat, poultary, fish and eggs) as detaild in Fig. 1.1, Fig. 1.2 and Fig. 1.3, respectively (Srilakshmi 2003).

Fig. 1.1 Basic four food groups Source: Srilakshmi (2003)

1. Introduction to Food Science

Fig. 1.2 Basic five food groups Source: Srilakshmi (2003)

Fig. 1.3 Basic seven food groups Source: Srilakshmi (2003)

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1.2.

A. Rakha, M.S. Butt and M.A. Khan

Food Science

Food Science is defined as “the study of the basic chemical, physical, biochemical and biophysical properties of foods and their constituents, and of changes during handling, preservation, processing, storage, distribution and preparation for consumption” (Bender 2006). Food Science is thus an applied science in which different disciplines are merged and it takes an absorbed concept from different fields of study such as biochemistry, physics, microbiology, biotechnology and nutrition based on fundamental principles. In ancient times when Food Science was not adequately developed, people had a little knowledge about the food nature and its functionality. Likewise, slight information was available about the impact of food on human body, concept of balanced diet, role of specific nutrients in health and diseases, food processing and preservation, fortification, enrichment, quality, safety and microbiology. However, with the advancement of research in the field of food science, innovation came in technology and focus moved towards automation of food plants and processing lines thereby making it easy to control and standardize processing parameters such as temperature, humidity, water contents, evenness of size etc. This resulted in improved efficiency of processing lines and thereby better quality end product. Furthermore, extraction and fortification techniques were also devloped to alter food value to cater the needs of vulnerable groups. Simultaneously, various types of packaging material i.e. rigid and flexible were developed to facilitate food handling, storage and transportation. Novel non-thermal food processing techniques had brought revolution in the pace of innovation and development of Food Science and Technology. Thus, modern consumers became aware about food composition, quality, safety, wholesomeness and relationship of food to health and disease.

1.3.

Food Technology

Food Technology is defined as “the use of information generated by food science, in the selection, transportation, processing, preservation, packaging, marketing and distribution of food, its affect on safe, nutritious and wholesome food consumption”. Alternatively, Food Technology is “the application of science and technology to the treatment, processing, preservation and till distribution of foods” (Bender 2006). In practice, food technology deals with the production processes of various foodstuffs based on of food science at large scale production and preservation along with development and analysis of food items at industrial scale that has been pivotal in the reduction of postharvest losses and at the same time value addition of raw food materials.

1. Introduction to Food Science

1.4.

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Food Scientist and Technologist

Food Scientist is responsible for the implementation of fundamental principles of foods for processing through the technology base knowledge and is supposed to: have deep knowledge and understanding of food, its constituents and nature, functionality and nutritional value, processing and preservation, fortification and analysis; development of palatable, wholesome and cheap food products; engaged to produce allergens free foods, novel and functional foods; focus on fortification technique to improve the nutritional value of the product; emphasize on enrichment techniques where nutrients are lost during processing. Food scientists are supposed to ensure safety and quality of foods and to promote international trade by harmonizing standards between the countries.

1.5.

Food Constituents

Food constituents are basically biochemicals which combine to make a specific food and are mainly derived from plants and animals present in different proportion, arrangements in food systems and impart their characteristic taste, texture, structure, color, flavor, energy and nutritional value. Two foods may have similar proportion of one or more constituents, yet they completely differ in physico-chemical and organoleptic properties. The basic concept of food constituents is necessary for better understanding of nature and composition of food.

1.6.

Nutrients and Non-nutrients

“Components of food that are needed by the body in adequate amounts in order to grow, reproduce and lead a normal healthy life include water, protein, fats, carbohydrates, minerals and vitamins” (Somati et al. 2007). Food supplies about forty essential nutrients which are the building blocks of thousands of substances necessary for growth and body functions. Major nutrients along with food sources are summarized in Table 1.1. Certain food components are classified as non-nutrients based on technical definition i.e., “organic constituents of food having no nutritional function. They may be toxins or beneficial substances like fibre or compounds that may improve palatability or carry pharmacological importance”. Colors, acids, phytates, tannins, phenolics etc. are other example of such food constituents. Energy production due to alcohol, after its metabolism, is non-nutrient mechanism because it has adverse effects on the body and is antagonistic to the definition of nutrients. Alcohol deteriorates the body development and growth, body’s self-repairing ability and organ’s functionality although it is a dense source of energy (7Kcal/g) which is almost 1.75 time

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1.6.1. Functions of the Nutrients Food is a combination of diverse constituents that perform various functions in the body as per nature of the constituents. Nutrients in foods are classified into four main categories based on their functions i.e. energy yielding, body building, regulating body processes and maintaining health. One or more food constituents are usually involved in each of the functions as energy generation, body growth and building, body regulatory processes and the ultimate target of health maintenance. The salient discussion on all the functions is briefly described in the following lines. 1.6.1.1. Provision of energy Food is the main source of energy production for the human and animal body that is generated through the process of regulatory metabolism. The body uses this energy to carry out activities in brain, and other organs/tissues. Foods with higher amounts of macronutrients (fats, carbohydrates, proteins and alcohol) are considered as the important and main sources of energy in the diet and is measured in terms of calories or kilo calorie (Kcal) i.e. amount of energy needed to raise the temperature of 1 kilogram of water through 1°C. One gram of carbohydrates, proteins fats and alcohol give 3.75, 4 and 9 Kcalories, respectively. Energy yielding foods include cereals, pulses, nuts, oilseeds, roots, tubers, meat, fish, pure carbohydrates (sugars and starch) and fats or oils. Inspite of being a good source of energy, most of the foods also provide micronutrients (vitamins and minerals). Cereals and pulses having considerable amounts of protein are also important source of vitamins and minerals. Fats of such foods are rich sources of fat soluble vitamins, whereas pure carbohydrates only provide energy. Generally stating, food rich in fat and oils are energy dense while those rich in dietary fibre provide least amount of energy although exhibit dietary benefits. Vegetables, fruits and cereal bran are rich in dietary fibre. 1.6.1.2. Growth and body building Protein is the building block of body tissues such as teeth, skin, bone and muscles. Thus, foods rich in protein are considered important in body building. Proteins indeed are important for building more than 80% of the dry weight of the muscles, whereas their deficiency in diet may lead to stunted growth. In young children and adolescents, protein rich diet attains an important factor for building of muscles and other body organs resulting in linear growth. Proteins are made up of 20 amino acids. Each protein has specific sequence of amino acids that determines their specific function, like collagen protein with strong and flexible helical structure specifically provides support to body structure. Protein rich foods are classified as: Milk, egg, meat and fish are rich in proteins of high biological value including all the essential amino acids in a balanced proportion for the synthesis of body tissues. Besides: Pulses, oilseeds and nuts are rich in protein but may not contain all the essential amino acids required by the human body. AApart from proteins, minerals are also involved in body building, the example of calcium is a vital and major constituent of bones along with phosphorous whereas, fluorine is integral component of teeth enamel. Foods rich in minerals such as

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calcium and iron include milk and dairy products, egg, meat, fish and green leafy vegetables etc. Lipids are the constituent of cells and play an important role in body building. Fat provides insulation to the body and protect vital body organs from damages. Likewise, fatty acids not only form the working base of the brain but also make up myelin coating of the neurons. Thus, intake of fat is correlated with lower rate of depression. 1.6.1.3. Regulation of body processes Food constitutents play an important role in providing protection and maintaining the body’s regulatory system. Homeostasis is the ability of an organism or system to maintain its parameters in normal range of values. Control of body temperature, pH, blood pressure and glucose concentration are the key examples of body functions performed by vitamin and minerals. 1.6.1.4. Maintenance of health Certain foods are thought to provide health benefits beyond the basic nutrition in reduceing risk of certain health conditions and diseases and are reffered as functional / nuetraceutical foods. Green leafy vegetables, coloured fruits, soybean, whole grains and spices are few examples of performing such functions as natural antioxidants and antimicrobials through phyto-chemicals, a vital component naturally present in plants. Food having phyto-chemicals may reduce the risk of age related chronic cardiovascular diseases, diabetes, certain types of cancers and high blood pressure. They also act as synergistic agents by allowing efficient absorption of the nutrients. Antioxidants are the chemicals that stops the activity of free radicals; which otherwise may damage the cells leading to cancer.

1.6.2. Classification of nutrients Nutrients are basically classified into 6 main classes as carbohydrates, fats, proteins, vitamins, minerals and water. Which are further divided into 4 sub-groups that include: a) macro and micro nutrients b) essential and non-essential nutrients, c) energy generating and non-energy generating and d) organic and inorganic nutrients with a brief description as stated below: 1.6.2.1. Macro and micro nutrients In this classification, nutrients are divided on the basis of their quantity or amount required by the body as macronutrients, in large quantities on daily basis in grams. Macronutrients include carbohydrates, proteins, fats and water. Mainly, macronutrients are the structural material (protein, fats and water) and energy (fats, carbohydrates and protein) for the growth as well as repair of the body. Micronutrients, on the other hand, are required in smaller quantities by the body on daily basis in milligrams or micrograms. Though these nutrients are required in less amounts, their significance can’t be denied. Deficiency of these nutrients may cause severe adverse effects on human body. Vitamins and minerals are categorized under micronutrients.

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1.6.2.2. Essential and non-essential nutrients Nutrients, based on necessity of dietary intake, are classified into essential nutrients that cannot be synthesized by body in adequate amount and essentially to meet their requirement through diet. The essential nutrients are associated with a vital body functions, vitamins, minerals, some of the amino acids that include (proline, threonine, valine, isoleucine, leucine, lysine, histidine, arginine and methionine) and fatty acids (linoleic acid, alpha linolenic acid). Conversely, non-essential nutrients are synthesized in satisfactory amount from essesntial nutrients or other moieties present in body that include some of the amino acids (alanine, arginine, asparagine, aspartic acid, cystein, cystine, glutamic acid, glycine, proline, serine and tyrosine etc.), fatty acids (monounsaturated fatty acids) and cholesterol etc. The significance of non-essential nutrients for the proper functioning of our body can’t be negated and the dietary deficiencies are nonexistant. 1.6.2.3. Energy yielding and non- energy yielding Energy generating mechanism through some of the nutrients in the body plays an important role in growth and development of body. Carbohydrates, proteins and fats are the main food constitutents for energy yielding is greater than carbohydrates and protein. On the other hand, vitamins, mineral and water are termed as non-energy generating nutrients mainly involved in body regulatory processes and take part in the body building. 1.6.2.4. Organic and inorganic nutrients Classification of nutrients is based on presence or absence of carbon in their chemical structure. Nutrients having carbon atom in their structures is reffered as organic nutrients, carbohydrates, proteins, lipids and vitamins are the examples. Apart from vitamins, the organic nutrients provide energy and hence serve as fuel for body functioning. Inorganic nutrients do not contain carbon atom in their structures, water and minerals are classified under this category.

1.7.

Macronutrients

1.7.1. Carbohydrates Carbohydrates are the organic compounds consisting of carbon, hydrogen, oxygen (Cn(H2O)n ) also known as hydrates of carbon. They are the major contributer of energy intake in our daily diet. The caloric contribution of carbohydrates varies from 40-80% depending upon socio-economic conditions of different contries. Carbohydrates constitute a major part of foods such as rice, bread, noodles and other grain based food products. Some important carbohydrates in our foods are sugars, dextrins, starches, cellulose, hemicellulose, gums and pectin and also considered as the major source of fiber in our diet. Carbohydrats are used as sweetner, thickner, stablizers and fat replacers in various food formulations. Scientific studies show that carbohydrates are 1% of the human body composition (Cui 2005). Carbohydrates can be classified into 3 main groups on the basis of their

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degree of polymerization as Simple carbohydrates / Sugars i.e. mono- and disaccharides; Oligosaccharides and Polysaccharides briefly detailed as: 1.7.1.1. Simple carbohydrates/sugars Simple carbohydrates are made up of one or two sugar molecules and are consequently named as monosaccharide and disaccharides, respectively. Both mono- and disaccharides are also termed as sugars that are rapidly digestible and are quicker source of energy. They are rich in calories and carry less nutritive value as their excessive intake is considered harmful for human health under certain conditions. The word monosaccharide is basically derived from mono, meaning "one", and saccharide, meaning "sugar". They are building blocks of carbohydrates also named as simple sugars which are sweet in taste containing 3 to 8 carbon atoms but only six carbon monosaccharides are common. They have a general formula CnH2nOn. Glucose, fructose, and galactose are the common examples of monosaccarides. The sweetness level of monosaccharide varies for glucose 0.74, fructose 1.6-1.9 and for galactose 0.35 when compared to sucrose taken as reference with sweetness level of 1.0. The chemical structure of fructose, glucose and galactose is shown below:

Disaccharides indicate “two sugars” or two monosaccrides are combined to make one molecule of disaccharides through linkage called glycosidic bond. Sucrose, maltose and lactose are common disaccharides and carry sweetness of 1.0, 0.32 and 0.16 respectively. Below is the example of sucrose formation (table sugar) in which one glucose and one fructose unit combine to form one molecule of sucrose through condensation process with the release of one water molecule (Izydorczyk 2005).

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1.7.1.2. Oligosaccharides The word “oligosaccharide” is derived from greek words, oligos means a few and sacchar means sugar. Oligosaccharides are the carboh...