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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.