Introduction to Food Science and Nutrition BND

Note prepared by Rewati Raman Bhattarai for BND

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1. Introduction to Food Science and Nutrition

Definition of important terms

1. Foods: Substances which can be ingested by living organisms and contain a range of

nutrients which can be metabolized to produce energy, and sustain life and growth.

2. Food science: Study of the characteristics of foods, including chemical properties,

biochemical properties, physical properties, physicochemical properties and biological

properties, and effects of these on the quality of products. Also covers application of this

information to development of new products and efficient food processing techniques.

3. Food technology: Application of a diversity of scientific and practical disciplines, including

chemistry, biology, physics and engineering, to the development of food products and to their

worldwide distribution.

4. Nutrition: Science of the relationship between foods, nutrients and health. It interprets the

relationship of food to the functioning of the living organism. It is concerned with the intake

of food, digestive processes, the liberation of energy, and the elimination of wastes, as well

as with all the syntheses that are essential for maintenance, growth, and reproduction.

5. Nutrients: Nutrients are essential dietary factors/substances, either naturally occurring or

synthesized, that are necessary for maintenance of the normal function of organisms. These

include carbohydrates, lipids, proteins, vitamins and minerals, water, and some unknown

substances.

6. Nutritionist: The nutritionist is a scientist working in the field of nutrition, who translates

the science of nutrition into the skill of furnishing optimal nourishment to people.

7. Diet: Selection by individuals or population groups of foods and beverages for consumption.

8. Dietetic foods: Products intended for consumption by individuals with metabolic disorders

or allergies, such as diabetic foods or gluten low foods. Also used to refer to foods providing

specific nutritional benefits to healthy individuals with particular dietary requirements, such

as infants or athletes.

9. Dietetics: Dietetics is a profession concerned with the science and art of human nutrition

care involved in the treatment of disease by modification of the diet.

10. Nutritional values: Indications of the level to which a food contributes to the overall diet.

These values depend on the quantity of food ingested and absorbed, and the amount of


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essential nutrients it contains. Nutritional values can be affected by cultivation conditions,

handling and storage practices, and processing.

11. Malnutrition: Condition resulting from inappropriate nutrition. Includes both inadequate and

excessive dietary intakes of nutrients and/or calories. Insufficient protein intake causes

kwashiorkor in children, and a diet deficient in all nutrients causes marasmus. Lack of

vitamins causes a wide variety of deficiency diseases, including scurvy, rickets, beriberi and

pellagra. Malnutrition may result from eating disorders, such as anorexia nervosa and bulimia

nervosa. Overnutrition can lead to toxicity and obesity.

12. Dietitians: Dietitians are experts in food and nutrition ("dietetics"). Dietitians supervise the preparation and service of food, develop modified diets, participate in research, and educate

individuals and groups on good nutritional habits.

13. Food quality: the features and characteristics of a food product, including its ability to satisfy stated or implied needs. It comprises characteristics such as safety, taste and

convenience, as well as the nutritional value of the product.

14. Food safety: the supply of food that will not cause harm to the consumer when it is prepared

or eaten according to its intended use.

15. Food security: the sustainable supply of food of adequate quantity and quality, available to

all members of the population.

16. Nutrition policy: a policy which seeks to improve and protect health and to improve the

quality of life for people of all ages by promoting healthy diets.

17. Nutrition security: the provision of a sustainable supply of adequate nutrients to all

members of the population.

18. Public health nutrition: the promotion of good health and the prevention of illness in the

population through nutrition and physical activity.

19. Health: a condition of physical, mental and social well-being, which implies, amongst other

things, the absence of disease.

20. Hygiene: Science of health and its preservation, or a practice or condition that is conducive

to the preservation of health.

21. Healthy diet: a diet that gives an individual his or her optimal health, i. e. contributes to

improve and protect health, and to reduce the risk of developing nutrition-related diseases.


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22. Sanitation: Establishment and maintenance of environmental conditions conducive to the

preservation of public health.

Scope of food science and nutrition

1. Dietitians: Dietitians plan food and nutrition programs, supervise meal preparation, and

oversee the serving of meals. They prevent and treat illnesses by promoting healthy eating

habits and recommending dietary modifications. Dietitians manage food service systems for

institutions such as hospitals and schools, promote sound eating habits through education,

and conduct research.

2. Clinical dietitian: Clinical dietitians provide nutritional services to patients in hospitals,

nursing care facilities, and other institutions. They assess patients' nutritional needs, develop

and implement nutrition programs, and evaluate and report the results.

3. Food Chemist: Food Chemists search for and put to practical use new knowledge about

foods and chemicals.

4. Food Scientist: Food scientists usually work in the food processing industry, universities, or

the Government to create and improve food products. They use their knowledge of

chemistry, physics, engineering, microbiology, biotechnology, and other sciences to develop

new or better ways of preserving, processing, packaging, storing, and delivering foods. Some

food scientists engage in basic research, discovering new food sources; analyzing food

content to determine levels of vitamins, fat, sugar, or protein; or searching for substitutes for

harmful or undesirable additives, such as nitrites. Others engage in applied research, finding

ways to improve the content of food or to remove harmful additives.

5. Catering manager: They have several responsibilities, including scheduling and managing

events, supervising food preparation and service, and cleanup.

6. Meat/Dairy scientist: Meat/dairy scientists usually work in the meat/dairy processing

industry, universities, or the Government to create and improve food products.

7. Production manager: Production managers plan, direct, and coordinate the production

activities required to produce the vast array of goods. They make sure that production meets

output and quality goals while remaining within budget.

8. Public health educator: Public Health Educators are employed primarily by State and local

departments of public health and, therefore, administer State-mandated programs. They strive

to get information out to the public on various health problems and make people aware of the

resources their programs have to help people to the community.

9. Quality assurance specialists: Quality assurance specialists enforce a wide range of laws,

regulations, policies, or procedures. They administer, support, and develop food safety and

quality assurance programs. They ensure standards for the production of manufactured and

packaged products are met. Production data and customer/consumer feedback are used to

improve product quality and customer satisfaction.

10. Regulatory affairs specialists: A Regulatory Affairs Specialist works within regulated

industries, such as food, agricultural, biotechnology, pharmaceuticals, health care, energy,


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and banking. Regulatory Affairs professionals usually have responsibility for Ensuring that

their companies comply with all of the regulations and laws pertaining to their business.

Applications of Nutrition & Dietetics

1. Education: Schools, colleges and hospitals require people to conduct courses in nutrition and

dietetics.

2. Food services: This can include a number of facilities in the commercial sector like food

manufacture, catering services and restaurants where nutrition professionals can do anything

from menu planning to meal preparation to promotion of the food products.

3. Health care: This is one of the largest and well-known functions of nutrition in hospitals and

clinics. Dietitians assist in treating patients with some big hospitals also providing scope for

research, food administration, teaching etc.

4. Information dissemination: This entails producing books, articles, promotions, television

programs on optimum dietary practices, since the present era is highly health-conscious.

5. Institutional catering: Nutrition and dietetics professionals are needed to plan and prepare

nutritious and well-balanced meals for schools, colleges, factories, offices, canteens, etc.

6. Research & development: R & D, as it is called, deals with conducting research projects on

various food items to ensure welfare from both the commercial food services viewpoint, plus

that of the health care provision.

7. Social welfare: Run by governmental organizations, this section is busy in improving the

eating habits and consequently, the health of the less-fortunate groups in society.

Role and responsibilities of food scientists and nutritionists

Food scientists are involved in many technical and scientific aspects of food. They are involved

in diverse areas with following activities:

1. To develop palatable, nutritious and low cost foods to combat food insecurity and eliminate

malnutrition.

2. To develop food preservation and storage methods to reduce food losses, eg. CA storage,

irradiation methods, quick freezing, quick cooking methods, etc.

3. To develop methods for meat tenderization by use of electric current or injection of

proteolytic enzymes.

4. To develop standards for optimal nutritional contents of diets.

5. To develop meaningful information to the public and to the creation of relevant, coherent

food law.

6. To determine effect of food processing and storage on nutrients, eg. effect of formulation on

bioavailability of nutrients, storage on nutrient content, etc.

7. To establish national and international food standards.


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8. To study safety issues related to foods, eg. prevent food poisoning (E. coli O157:H7, C.

botulinum, salmonella enteritidis), eliminate food toxicants.

9. To develop processes to eliminate or reduce pesticide residues in food.

10. To improve existing and develop new products.

11. To alter nutrient content of foods, eg. reducing calories or adding vitamins or minerals.

12. To produce flavors by enzymes using basic raw material substrates, eg. cooked meat flavors

from fats, fruity flavor from carbohydrates, etc.

13. To use genetic engineering and biotechnology to produce desired products, eg. cloning of

rennin producing genes into bacteria.

14. Automation in food industry.

15. To produce proteins from low cost cellulosic materials.

A nutritionist is a person with the recognized qualification in nutrition who applies the science of

nutrition to the feeding and education of groups of people and individual in a health and disease.

A nutritionist may be administrative or consultant.

The role and responsibilities of administrative nutritionist are:

1. Plans, directs, controls and evaluates the food and nutrition service system.

2. Develops short and long term departmental plans and programs consistent with the policies

of organization.

3. Plans, conducts and evaluates orientation and in-service educational programs.

4. Manages and controls fiscal resources and recommends the budget.

5. Utilizes human efforts and facilitates the resources efficiently and effectively in the nutrition

related program.

6. Coordinates and integrates the clinical and administrative aspects of nutrition to provide the

quality nutritional care.

7. Establish and maintain standards of food production and service, sanitation, safety and

security.

8. Develops the menu pattern and evaluates the client acceptance.

9. Interprets, evaluates and utilizes pertinent current research relating to nutritional care.

10. Makes plan for nutritional survey and conducts training for man power development.

Role and responsibilities of consultant nutritionist are:

1. Evaluates and monitors food and nutrition service system making recommendations for

confirmation.

2. Plans, conducts and organize orientation and in-service educational programs for food and

nutrition service.

3. Develops budget proposals and recommends the procedure for cost control.


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4. Recommends and monitors standards for sanitation, safety and security in food and nutrition

service system.

5. Evaluates and implements the nutritional care.

6. Develops menu pattern.

7. Consult with health care team about the nutritional care of clients.

8. Maintains inter and intra departmental communication and public relation.

9. Access develop implement and evaluate nutritional plans and provide follow up including written reports.

10. Carry out design for establishment of food service system as well as develop specifications for procurement of equipments and supplies.


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2. Carbohydrates

Include compounds like sugars, starches, glycogen, cellulose, dextrins and gums.

Obtained mainly from plants by a process called photosynthesis:

xCO2 + yH2O Sunlight

Cx (H2O)y Chlorophyll

Carbohydrates play a vital role in our daily life. They provide us three basic

necessities of life,

1. Food (in the form of starch)

2. Clothing (cotton, linen, rayon ie. Cellulose)

3. Shelter (wood, furniture ie. Cellulose)

Old definition

The name carbohydrate (meaning hydrate of carbon) was originally given to a class of

compounds containing only carbon, hydrogen and oxygen; the hydrogen and oxygen being

present in the same ratio as in water.

The General Formula: Cx (H2O)y

Limitations of old definition

1. A number of compounds such as rhamnose, (C6H12O5) and deoxyribose (C5H10O4) are

known which are carbohydrates by their chemical behavior but cannot be represented

as hydrates of carbon.

2. The other substances like formaldehyde (HCHO, CH2O) and acetic acid [CH3COOH,

C2 (H2O)2] which do not behave like carbohydrates but can be represented by General

Formula Cx (H2O)y.

3. Carbon is not known to form hydrates.

Modern definition

Carbohydrates are defined as polyhydroxy aldehydes or polyhydroxy ketones (or compounds

thereof), or polymers that can liberate these compounds upon hydrolysis (Fig. 1.1). With

some exceptions, carbohydrates have the general formula: Cn H2nOn, where n refers to any

positive integer. Carbohydrates can also be represented by (CH2O)n where n 3.


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Fig. 1.1 Examples of polyhydroxy aldehyde and polyhydroxy ketone

Classification of carbohydrates

Carbohydrates may be classified into three broad groups, namely:

1. Monosaccharide: Monosaccharides are the simplest units of carbohydrate and cannot be

hydrolyzed further into smaller units. They are often called simple sugars or neutral sugars.

Examples are: glucose, fructose, galactose, ribose, xylose, arabinose, ribulose, etc.

2. Oligosaccharide: Oligosaccharides are carbohydrate polymers of 2-10 sugar units. The

oligosaccharides containing two monosaccharide units are called disaccharides, and those

containing three units, trisaccharides. The oligosaccharides most frequently encountered in

nature are disaccharides, e.g., sucrose, lactose, maltose, and melibiose. The trisaccharide of

importance is raffinose.

Disaccharides yield two moles of monosaccharides on hydrolysis (by chemical or

enzymatic means). Some examples of oligosaccharides and their hydrolytic products are as

follows:

Sucrose hydrolysis

Glucose + Fructose

Maltose hydrolysis

Glucose + Glucose

Lactose hydrolysis

Glucose + Galactose

3. Polysaccharide: Polysaccharides are formed when a large number of monosaccharide

molecules are joined together with the elimination of water molecules. They are regarded as

condensation polymers. Examples are: starch, glycogen, dextrin, chitin, hyaluronic acid,

pectin, etc.

Glucose

Glucose is the most common monosaccharide. It is known as dextrose because it occurs in

nature principally as the optically active dextrorotatory isomer.


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Glucose occurs in nature in free as well as in combined state. It occurs in large quantities

(20%) in ripe grapes and that is why it is called grape sugar. It also occurs in honey and most

of the other sweet fruits (such as mangoes, apples, peaches, pears, etc.). In the combined

state, it occurs in glycosides, disaccharides and polysaccharides. It is an essential constituent

of human blood. The blood normally contains 64-110mg glucose per 100ml.

Structure of glucose

The empirical formula of glucose is C6H12O6. The structure of glucose can be represented by

two methods, viz., (i) Fischer projection formula (open chain form), and (ii) Haworth

formula (ring form). See Fig. 1.2 (a) and (b) for the explanation. The open chain form and

the ring form account for 0.01 and 99.99% of glucose.

Fig. 1.2(a) Fischer projection formula and Haworth formula of glucose

Fig. 1.2(b) Simplified Haworth formula of glucose (the straight lines represent OH

group)

Preparation


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1. From sucrose (cane-sugar): When sucrose is hydrolysed by boiling with dil. HCl or

H2SO4 in alcoholic solution, an equimolar mixture of glucose and fructose is

obtained.

C12H22O11 + H2O H+ C6H12O6 + C6H12O6

2. From starch: Commercially glucose is obtained by hydrolysis of starch by boiling it

with dil. H2SO4 at 393 k under pressure.

(C6H12O5)n + nH2O H+ nC6H12O6

393 K, 2-3 atm

General properties of glucose

Physical properties

Glucose is a white crystalline solid with a melting point of 146C.

When crystallized from cold water, it forms glucose monohydrate (C6H12O6H2O),

melting point 86C.

It is extremely soluble in water and is about 3/4th as sweet as cane sugar.

Chemical properties

Reducing property

Not only glucose but all monosaccharides have a reducing property. They can reduce metal

ions of copper, bismuth, and silver. They are therefore called reducing sugars. The reducing

property is due to the presence of free (in the chain form) or potentially free (in the ring

form) aldehyde or ketone function.

The reaction with cupric ion is of great practical significance. It is used in the qualitative

as well as quantitative test of reducing sugars, particularly glucose. This is the basis of

Benedict test and Fehling test used routinely for glucose determination in blood, urine, etc.

The basic reaction is as follows:

Reducing sugar + Cu++ (cupric) Oxidized sugar + Cu+ (cuprous)

Blue color Red color

Many disaccharides, such as maltose, lactose and melibiose also have potentially free

aldehyde in their molecules and are therefore reducing sugars. Sucrose, on the other hand, is

not a reducing sugar because it has no free aldehyde or ketone group for the reducing

reaction.

Fig. 1.3 Anomerism in glucose

Fructose


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The name fructose probably implies fruit sugar as it is found along with glucose in the

juices of ripe fruits and honey. In the combined state, it is found in inulin (polymer of

fructose found in artichoke, dandelion, etc.) and sucrose. In man, it is a normal constituent of

blood (0.5-5mg/100ml). In honey and grape juice, glucose and fructose are present in the

ratio of ~ 1:1. In most normal diets, fructose contributes about 15-50% of the total

carbohydrate intake.

The molecular formula of fructose is the same as that of glucose C6H12O6. However, it is a

ketohexose. It is also called levulose because the naturally occurring form of fructose is

levorotatory.

Structure of fructose

Fructose differs from other glucose isomers in that the anomeric carbon is C2 rather than C1.

The chain form of fructose is given in Fig. 1.1. The pyranose form of fructose has been

proposed by analogy to glucose. However, the sugar exists in the furanose form (5-

membered ring, form) in oligosaccharides such as sucrose. The furanose form is shown in

Fig. 1.4.

Fig. 1.4 Anomerism in fructose

Some important structures of carbohydrates (Fig. 1.5-1.8):

Fig. 1.5 Sucrose molecule


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Fig. 1.6 Structure of maltose molecule

Fig. 1.7 Haworth Formula of Lactose

Fig. 1.8 Haworth Formula of Melibiose

Starch, Amylum (C6H12O5)n.

The value of n (200-1000) varies from source to source. It is the chief food reserve material

or storage polysaccharide of plants and is found mainly in seeds, roots, tubers, etc. Wheat,

maize, rice, potatoes, barley, bananas and sorghum are the main sources of starch. Starch

occurs in the form of granules (Fig. 1.9), which vary in shape and size depending upon their

plant source.

Fig. 1.9 Starch granule of potato


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Properties

I. Starch is a white amorphous powder sparingly soluble in water.

II. On hydrolysis with dilute mineral acids or enzymes, starch breaks down first to

smaller molecules (n>n), then to maltose and finally to D- glucose.

(C6H12O5)n H+/ H

2O (C6H12O5)n

H+/ H2

O C12H22O11 H+/ H

2O C6H12O6

Starch Maltose or, Maltase D-glucose

III. Starch is non-reducing saccharide. It neither reduces Tollens reagent (or Fehlings solution ) nor forms an osazone*.

*Osazone: All reducing sugars react with excess of phenylhydrazine to form osazones.

Composition

Starch is not a single compound but it is a mixture of two components --- a water soluble

component called amylase (15-20%) and a water insoluble component called amylopectin

(80-85%).

The aqueous solution of amylase gives a blue color with iodine solution due to the

formation of an inclusion complex. The blue color, however, disappears on heating and

reappears on cooling.

Amylopectin, on the other hand, does not give blue color with iodine solution.

Structure of amylose:

Amylose is a chain-like linear polymer, the glucose units being mostly linked through -1,4-

glucosidic bonds. Consequently, each molecule of amylose has one reducing and one non-

reducing end (Fig. 1.10). A molecule of amylase may contain 200-1000 units of glucose

units.

H

Fig. 1.10 Structure of amylose

Structure of amylopectin:

It is a highly branched polymer. It is formed by non-random -1,6-branching of the

amylose-type -1,4-D-glucose structure(Fig. 1.11). Each amylopectin molecule contains a

million or so residues, about 5% of which form the branch point.


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Fig. 1.11 Structure of starch

Uses and functionality of starch

Starch finds uses in fast food, sweets, sausages, tablets (as a filler), and corrugated

boards, etc., and plays a prominent part in our everyday life.

Starch can be used as thickener (in sauces, gravies and baby foods), water binder (in

sausages), emulsion stabilizer (in fee cream) and gelling agent.

Starch is recently being used, singly or in combination, for the manufacture of

biodegradable packaging material.

Starch is also a very important raw material for the manufacture of caramel (color)

and the microbial production of glutamic acid.

Cellulose (C6H10O5)n

Cellulose is the chief structural material of cell walls of all trees and other plants. Wood is

50% cellulose, while cotton wool is almost pure cellulose. Other sources of cellulose are

straw, corncobs, bagasse, and similar agricultural wastes.

Chemistry

Cellulose is a straight chain polysaccharide of D-glucose (or more specifically, cellobiose

units). Glucose units are joined by -1,4-glycosidic linkage. The number of glucose units in a

cellulose molecule varies from 2000 to 14000. The partial structure of cellulose is as in Fig.1.

12.


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Fig. 1.12 Partial structure of cellulose

Properties

Cellulose is fibrous in nature.

It is a colorless solid having no melting point.

It decomposes on strong heating.

It is insoluble in water and most organic solvents.

Hydrolysis of cellulose in dilute HCl or H2SO4 gives D-glucose. Cellobiose is formed

in case of incomplete hydrolysis.

Like starch, it is also non-reducing.

Q. Why is cellulose not digestible by humans?

The cattle, goats and other ruminants have digestive enzymes (cellulases) capable of

hydrolyzing cellulose into glucose. Consequently, these animals can feed directly on

cellulose (grass, straw). Man and many other mammals lack the necessary enzymes in their

digestive tract, and they cannot use cellulose as foodstuff.

Functins of Carbohydrates

The carbohydrates perform two important functions in living bodies.

They act as biofuels to provide energy for functioning of living organisms.

They act as constituents of cell membrane and cell wall.

They exert sparing action on proteins.

They are essential for the oxidation of fat.

They are indespensible for nervous system.

Documents

Introduction to Food Science and Nutrition BND