FOOD Science AND Technology. Module pdf PDF

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The notes is meant for student pursuing human nutrition and it orient them to the food processing and preservation techniques...

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FOOD SCIENCE & TECHNOLOGY MODULE

FOOD SCIENCE AND TECHNOLOGY INTRODUCTION Food is anything solid or liquid which when swallowed digested and assimilated nourishes the body Food science – is the study of nature, composition and the chemical and physical changes that occur under valid conditions of storage, processing and use of food components. Food technology – is the application of the principals of food science and engineering so that food of better quality is grown, processed and preserved in large quantities. The different areas of study in food science and technology include : Food chemistry  Food microbiology  Food engineering  Food processing The role of food science and tech in dietetic therapy is as follows 1. Meal planning for nutrient adequacy 2. Safety of food 3. Intervention programs for individuals, grouped and population 4. Increased food due to reduced wastage and deterioration Food science and technology and food security Food security – it is the access at all times to adequate safe, nutritious and healthy food that meets dietary needs using socially acceptable ways for individuals and communities Food insecurity can be caused by:i)

Low food production

ii)

Seasonal food shortages

iii)

High food prices

iv)

High levels of unemployment

v)

Low level of nutrition education

vi)

Cultural factors and taboos

vii)

Policy failures

FOOD SCIENCE & TECHNOLOGY MODULE

Main areas of intervention of FST in food security 1. Food production 2. Food fortification 3. Micronutrients supplementation 4. Education for dietary change Revision questions 1. Define the following terms i)

Food

ii)

Food security

iii)

Nutrients

2. Differentiate between food science and food technology 3. Explain the role of food science and tch in dietetic therapy 4. Highlight the area of FST intervention in food security FOOD COMPOSITION The food we eat is made up of three major kinds of nutrients  Proteins  Carbohydrates  Fats It is also composed of vitamins, minerals and fibre Food have been classified into different grups depending upon the nutritive value for convenience of planning diet. The major food groups include  Cereals and cereal products  Fruits and vegetables  Meat and meat products  Poultry and eggs  Milk and milk products  Legume and root tubers  Sea foods and fish 1. Briefly discuss in details the major classification for foods

FOOD SCIENCE & TECHNOLOGY MODULE

ENZYMES They are proteins that occur in nature and speed up bio- chemical processes that would otherwise take a long time.In food industry, enzymes are used to produce, food products e.g. wine, cheese, corn syrup, baked foods etc. Application of enzymes allows the manufacturers to produce more of a particular product in a shorter amount of time thus increasing profit.When enzymes are used in the processing of foods, they are not considered food themselves; they are not required to be listed on the label of end product. General characteristics of enzymes and factors affecting in food processing 1. Specificity Enzymes are highly specific for their substances e.g. maltose acts only on maltose hydrolyzing it to two molecules of glucose. The bases of enzyme specifically are the existence of an active site in the enzyme. This is the region where the substrate comes into contact with the enzyme. 2. Effect of temperature Enzyme activity proceed very slowly at low temp, as temp increases in temp also increases the denaturization of proteins since enzymes are proteins in nature and hence leads to inactive of enzymes. Maximum activity of most enzymes ranges between 30-40oc and inactivation sets in and is complete above 50-550c

enzyme activity

30oc

40oc Temp

This explains why fruits and vegetables that are prone to enzymatic browning are branched or subjected to boiling H2O or live steam for a short period of time to inactivate enzymes.An extreme decrease in temperature also inactivate the enzymes.

FOOD SCIENCE & TECHNOLOGY MODULE

3.

effects of PH

PH is what defines the acidity and alkalinity of a medium and hence determines the enzyme activity. All enzymes are active only within a narrow PH range and for every enzyme, there is a PH of maximum activity known as optimum PH. most enzymes are active in PH range 4.5 -8.0

Enzyme activity

4.5 4.

PH

8.0

Co-factors.

The reaction of enzyme is supported by enzyme co-factors also referred to as co-enzymes e.g. Zinc 5. Inhibitors These are substances that prevent normal functioning of enzymes Types of enzymes of concern in food technology enzymes are categorized according to compounds they act upon Examples of enzymes:i)

Carbohydrates e.g. Maltose, sucrose’s, amylases, glycosidase, glycosidase

ii)

Protein e.g. Peptidases, pepsin, trypsin and proteases

iii)

Fats e.g. Lipases

iv)

Vitamin e.g. hydrolyses, oxidizes

Effects of enzymes on quality of foods 1. Enzymatic browning Browning can be observed on the cut surfaces of light coloured fruits and vegetation such as apples , bananas etc. due to enzymatic action.The formation of brown colour is due to action enzyme phenolase (polyphenoloxidase) tyrosinase/catecholase).When foods containing such substrate are cut and exposed to air rapid browning of the cut surface take place

FOOD SCIENCE & TECHNOLOGY MODULE

2. Microbial spoilage This occurs mostly in fruits where enzymes hasten the ripening process and beyond a certain stage, they render the fruits too soft and unfit to eat. If there is a bruised spot in the fruit, yeast would grow and produce enzymes which could spoil the fruit 3. Oxidation of ascorbic acid Being a labile vitamin. Ascorbic acid is easily oxidized especially in presence of enzyme ascorbic oxidase. This is facilitated by long exposure to air after cutting vegetable before cooking or serving. Application of enzymes in food production Enzymes in bread making By the action of amylase in flour used in bread making, dextrins and maltose are formed and this provide the fermentable sugar for the yeast cells. This enzymatic reactions continue in the baking process till the enzyme activity is destroyed as the oven temp rises. The time and extent of changes due to carbohydrates in the flour determines the softness, crust colour , volume and texture of baked product. Production of alcoholic drinks Peptic enzymes play an important part in fruit ripening maintaining the viscosity of processed foods and in textural changes. The haziness noticed in wines is due to peptic substances. Peptinases are used in classifying alcoholic drinks. Application meal tenderization The art of using enzyme for tenderizing meat is an old one. Wrapping of meat on pawpaw or papaya leaves before cooking results in tenderization. this is the result of the action of enzyme papain on meat proteins.

FOOD SCIENCE & TECHNOLOGY MODULE

Other enzymes used for meat tenderization are -

Bromelin from pineapples

-

Ficin from figs

-

Trypsin from pancrease

-

Fungala enzymesx

The enzyme catalyse the hydrolases of meat proteins and also hydrolyse the elastin or connective tissue .Tenderizing enzymes remain active until the meat is heated .papain is inactive at 55oc Cheese making Enzymes help in the ripening of cheese. these enxymes are formed by micro-organisms and they act on peptones and peptide and other substances to form produvts like amino acids , amines, fatty acids, esters, aldetydes, alcohols and ketones that gives its characterstic flavor. Tea production The important constituent of tea contributing to the flavor are caffeine, polyphenols and essential oils.Polyphenols present in tea have anti-oxidant activity.During fermentation, polyphenol substances/stannins

roxidized

by

phenoloxidase

and

some

new

phenolye

products

result.Enzymes help to cause desirable enzymatic browning during fermentation.The higher the content of enzymes in tea leaves the better the quality. Revision questions I. II.

Define an enzyme Discuss general characteristics of enzyme and factors affecting in food processing

FOOD SCIENCE & TECHNOLOGY MODULE

FOOD ADDITIVES They are substances not naturally present in a food but added during its preparation and remaining in the finished product to preserve flavor, enhance taste and appearance. They include anything added during the production, processing treatment, packaging, transport and storage of a food. Importance /functions of food additives 1. Maintain product consistency e.g. Emulsifier stabilizer anti-caking agents etc. 2. To improve or preserve the nutrient value-many foods and drinks are fortified and enriched to improve the nutritional status of the population e.g. Vitamins, mineral that may be low or completely lacking in a food. 3. Maintain the wholesomeness of foods- preservatives reduce the spoilage that air, fungi, bacteria or yeast can cause . They also keep fresh from turning brown when exposed to air. 4. Controlling the acidity and alkalinity and provide leavening .Specific additives help to change the acid base balance of food to obtain that taste color and flavor. Leavening agents that release acids when they are heated react with baking soda to help biscuits, cakes and other baked products rise. 5. They provide colour and enhance flavor Addititives could be natural ( e.g turmeric) or synthetic. 6. To produce easy to prepare convenient foods in a society that is busy and spends less time in the kitchen than in the past. 7. To produce new food products that is of different shapes and colour. Advantages of food additives 1. They allow our growing urban population to have a variety of foods all year round. 2. They make many possible convenient without the inconvenience of daily shopping. 3. They help to reduce food spoilage and reduce the risk of food poisoning. 4. They help to improve colour and flavor of food thus increasing customer acceptability of the food product.

FOOD SCIENCE & TECHNOLOGY MODULE

Disadvantages of using food additives. 1. Some food additives are toxic if a large amount is used e.g. Sodium benzoate. 2. Some food additives may be casinogenic e.g. Sodium nitrate has showed to cause cancer in mice and may also cause cancer to human beings. Many food colourings used in the past has showed to cause cancer. 3. Some additives may have side effects such as allergies and hyperactivity. Types of food additives Anti-oxidants – they are added to fats and fat containing substances to retard oxidation and thereby prolong their wholesomeness, palatability and keeping time. It should not contribute an objectionable odour, flavor or colour to the fat or food in which it is present. Antioxidant include :- phenolic compounds, tocopherols etc. Tocopherols act as biological antioxidants in plant and animal tissue but they are less or rarely used coz they are more expensive than synthetic antioxidants. Antioxidants also help to reduce the browning of cut fruits and vegetables (maillard reactions) 2. Acid –modifiers They are used to control acidity and alkalinity of a food. They are also used to develop acid flavor in baking powder in sweets, setting off the jam etc. Examples of acids used include:- citric, tartanic acid, malic acid, acetic acid (vinegar), lactic acid from dairy foods ascorbic acid etc. Foaming agents They are used to ensure that bubbles are evenly distributed e.g. Icecream 4. Sweeteners They are substances rather than carbohydrates which have characteristic sweetness e.g. Sorbital found in fruits. It is approx ½ as sweet as sucrose. It is stable in high temperature therefore used to make confectionary e.g. Sweets and jam. It can be used by diabetics.

FOOD SCIENCE & TECHNOLOGY MODULE

Saccharine is 300 times sweeter than sucrose. It is popular with the diet conscious people. It is used in production of soft drinks and diabetic foods. However it has an after taste. Aspartame – it is a mixture of aspartic acid and phenyplanine. It is 200 times sweater than sucrose.. It is suitable if sweetening soft drinks. However, it is unsuitable for children suffering from a genetic deficiency called phenyl ketonuria 5. Thickeners They are added to processed food products to thicken basically liquids e.g. soups. 6. Nutritive agents. During the processing of some foods, nutrients are lost and this may be replaced by the manufacturer by addition of nutrients to enrich or fortify them e.g. Vit A and D are added to margarine and calcium is added to white bread, by law fruit juices have extra vit C added, iodine is added to salt. 7. Flavor enhancers They are added to strengthen the flavor of the end product e.g. strawberry, vanilla, monosodium glutamate (for meat products) 8. Humectants They are to food to make them soft and prevent them from going dry e.g. glycerol found in cake mixes. 9. ABT-caking agents They are added to prevent powders from caking in the packet e.g. calcium silicate added to icing sugar to stop it going lumpy Other food additives includes anti-foaming agents e.g. in pineapple juice to prevent it from frothing too much. Flour improvers, raising agents, glazing agents are added to give a shine to confectionery.

FOOD SCIENCE & TECHNOLOGY MODULE

Legislation of food additives The use food and drug administration has a list of food additives that are considered safe. Many have not been tested but are considered safe by most scientists. Substances are put on the GRAS list (Generally Recognized As Safe list). Some that are allowed may be harmful but should be on the label. Prohibitions on food additives controls to use and limits of any food additives are outlined by the food law. The primary aims of the legislation controlling are: To protect the health of consumers  To prevent food fraud The food safety act prohibits addition to food of any substances that may be injurious to health. Revision Questions 1. Explain the meaning and importance of food additives in foods 2. Define a food additive 3. Distinguish various types of food additive 4. Apply various types of food additives in food production 5. Explain the legislation on food additives

FOOD SCIENCE & TECHNOLOGY MODULE

CONTAMINANTS Contaminants – are residues that become part of food as a result of processing, handling and distribution of food. Occurrence and types of contaminants:The main contaminants in food industry include:1. Geo – contaminants e.g. heavy metals like lead and mercury 2. Pesticides – are substances intended for preventing destroying or repelling any pest. A pesticide is generally a chemical or biological agent that through its effect deters/ incapacitate /kills or otherwise discourages pests. They include organochloride, organophosphates, herbicide, fertilizers, anti-biotics, hormones (like those found in chicken, beef and veal) 3. Industrial fall-out – these refers to the surface contamination originating from sources such as overhead electrical cables, metals in the manufacturing factory etc. Heavy metal poisoning from elements such as lead and mercury caused by industrial fallout eventually build in the tissues of predators such shark and whale. -

Industrial fall-out include acid rain and chlorofloral carbons (CFC)

Methods of control of contaminants is food industry Prohibition:Legislative authorities have been taken numerous steps to protect consumer against food that is detrimental to his health Withdrawal:Where specific premises fail to meet the conditions of approval or licensing, the appropriate approval or license may be withdrawn.Where raw agricultural products are produced, market withdrawal capabilities from the point of processing are essential Controlling application.:Official standards have been prescribed if ordinary fertilizer and for each type of a fertilizer have a minimum and maximum amount that can be used. Enforcing standards on them:Environment protection agencies give licenses for use e.g. enforcing pesticides requirement. Revision Questions 1. Identify the type and sources of food contaminants 2. Explain the methods used to control contamination in food industries.

FOOD SCIENCE & TECHNOLOGY MODULE

TOXIC CONSTITUENTS AND ANTI-NUTRIENTS (Toxins) Toxic constituents are substances created by plants and animals that are poisonous to human. Anti-inutrients are natural or synthetic compounds that interfere with absorption of nutrients in the human body. Occurrence and type of toxic constituents 1. Cyanogenic glycosides They are present in a number of food plants and seeds hydrogen cyanide is released from cynogenic glycosides when fresh plant materials are brocken down e.g. as in chewing which allows enzymes and cyanogenic glycosides to come together releasing hydrogen cyanide. Cassava is detoxified by chopping and griding in running H2O prior to preparation Cyanide is one of the most potent rapidly acting poisonous known. Cyanide inhibit active sites of cells causing them to die very quickly. The human body rapidly detoxifies cyanide and an adult human can withstand 50-60 ppm for an 1hr without serious consequences However , exposure to concentrations of 200-500 ppm for 30 minutes is usually fatal. 2. Dhurrin in sorghum/millet Dhurrin is found mainly in the leaves and germinating seeds of sorghum. It plays the role of defense against herbivore attack. The content of cynanogenic glycoside dhurrin in sorghum vary depending on plant age and growth conditions. The cyanide potential is highest shortly after onset of germination. 3. Amygdelin (Vit BIT/Laterine) -

It mostly occurs in nuts and almonds.It is also found in plants such as lima beans and sorghum.Cyanide is believed to be the active cancer willing ingredient in latelline.

-

Amygdelin is also common in macadamia nutsWhen amygdelin containing seeds are crushed and moistened free cyanide is formed.

FOOD SCIENCE & TECHNOLOGY MODULE

4. Lytharism factor. Lytharism is a paralytic disease affecting lower limbs toxic substances interfere with formation of normal collagen in connective tissue.It is present in pulses.Most commonly found in India. 5. Favism factor (vifabafactor) Found in vicafaba beans Favism is haemolytic anaemia It may cause death within 24-48 hrs of attack This is brought about by eating broad beans and it affects metabolism of glutathione 6. Mycotoxins  It is a toxic secondary metabolite produced by organism of the fungus kingdom commonly known as moulds.  The mycotoxin is usually reserved for the toxic chemical products produced by fungi readily colonize crops.  Mycotoxins can appear in the food chain as a result of fungal infection of crops either by eating directly by humans or by –being used as livestock feed.  Tempereture treatment such as cooking and freezing do not destroy mycotoxins thus mycotoxins greatly resist decomposition of being broken down in digestion so they remain in the food chain in meat and dairy products. Types of anti-nutrients 1. Enzyme inhibitors They are molecules that bind enzymes and decrease their activity. Not all molecules that bind enzymes are inhibitors. Enzyme activators bind to enzymes and increase their enzymatic activities. Proteins can be natural poisons or anti-nutrients e.g. Trypsin inhibitors, amylase inhibitor Amylase inhibitors are also known as starch locus because they contain substances that prevent dietary starches from being absorbed by the body. Amylase inhibitor can be extracted from several types of plants especially those in legume family. Currently available amylase inhibitors are extracted either from kidney ...