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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
- Meal planning for nutrient adequacy
- Safety of food
- Intervention programs for individuals, grouped and population
- 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 Main areas of intervention of FST in food security
- Food production
- Food fortification
- Micronutrients supplementation
- Education for dietary change Revision questions
- Define the following terms i) Food ii) Food security iii) Nutrients
- Differentiate between food science and food technology
- Explain the role of food science and tch in dietetic therapy
- 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
extreme decrease
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. Enzyme activity 4. 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
- 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
4.5PH 8.
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. Define an enzyme II. Discuss general characteristics of enzyme and factors affecting in food processing 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
- Maintain product consistency e.g. Emulsifier stabilizer anti-caking agents etc.
- 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.
- 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.
- 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.
- They provide colour and enhance flavor Addititives could be natural ( e.g turmeric) or synthetic.
- To produce easy to prepare convenient foods in a society that is busy and spends less time in the kitchen than in the past.
- To produce new food products that is of different shapes and colour. Advantages of food additives
- They allow our growing urban population to have a variety of foods all year round.
- They make many possible convenient without the inconvenience of daily shopping.
- They help to reduce food spoilage and reduce the risk of food poisoning.
- They help to improve colour and flavor of food thus increasing customer acceptability of the food product. Disadvantages of using food additives.
- Some food additives are toxic if a large amount is used e.g. Sodium benzoate.
- 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.
- 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
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. 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
- Explain the meaning and importance of food additives in foods
- Define a food additive
- Distinguish various types of food additive
- Apply various types of food additives in food production
- Explain the legislation on food additives
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:-
- Geo – contaminants e.g. heavy metals like lead and mercury
- 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)
- 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 fall- out 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
- Identify the type and sources of food contaminants
- Explain the methods used to control contamination in food industries.
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
- 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 bean white and
red kidney bean or wheat. Amylase inhibitors are not essential nutrients and are normally not produced in the body and so no deficiency is possible. High content of amylase inhibitors reduce carbohydrate absorption in humans
2. Avidin in eggs Avidin is a biotin protein produced in the oviducts of birds, reptiles and amphibians deposited in the whites of their eggs. Raw egg white contains a protein called avidin which deactivates biotin Biotin is necessary for proper carbohydrate, protein and fat metabolism and for proper utilization of other B complex vitamins as well as healthy hair and skin 3. Goitrogens They are substances that suppress thyroid gland by interfering with iodine uptake which can as a result cause enlargement of thyroid gland. They are common constituents of plants belonging to the crucifer family e.g.broccoli, cauliflower, kales, mustard seeds etc. 4. Glucosinotes Plants use substances derived from glucosinolates as a natural defence against herbivores. These substances are responsible for the sharp and better taste found in food such as mustard, cauliflower, broccolis turnips 5. Phytic and phenolic compounds Phytates are phosphorous compounds found primarily in cereal grains, legumes and nuts. They bind with minerals such as iron, calcium and zinc thus interfering with their absorption in the body. Phytic are phytic acids are storage form of phosphorus in the fiber of raw whole grains, legumes seeds and nuts. Phytates are not released through the digestive process Through leavening phytic acid and phytates cause no problem. They are also destroyed through baking food processing.
ASSIGNMENT 1
Discuss the various methods of removal or detoxification of
constituents and anti-nutrient from food.
NB: To be handed in with your examination answer booklet. FOOD PRESERVATION It’s the process of treating and handling food to stop or slow down spoilage, loss of quality edibility and nutritional value thus allowing longer storage. It usually involves preventing the growth of bacteria, yeast, fungi and other micro organisms as well as retarding the oxidation of fats which cause rancidity. Reasons /roles of food preservation
- To eliminate any potential micro biology harm to the consumer.
- T o add variety to the diet by making foods available out of season
- To produce new products out of the food e.g. in fermentation also in the germ making
- Maintain nutritional value of the food production of safe food products.
- Maintain the quality of food and increase the shelf life Principles of food preservation
- Controlling of micro-organisms This can be done in the following ways: Keeping microorganisms out of the food (asepsis) Removing microorganisms from the food e.g. through filtration Killing microorganisms and the spores Delay microbial growth
- Controlling self- decomposition. This can be done by Inactivating endogenous enzymes e.g. in blanching
- Preventing or delaying chemical reactions of the food e.g. in fats
- Controlling insects, rodents, birds, and other physical cause of food spoilage METHODS OF FOOD PRESERVATION
Methods of preservation can be broadly classified into (3)
- Physical methods e.g. pasteurization ,sterlizaton, control of water content ,radiation etc
- Chemical methods e.g. salting ,curing, smoking and use of preservatives
- Biological methods e.g. fermentation Food /radiation Ionizing radiation can kill microorganisms thus used in food preservation When food is radiated, energy passes through it and kills harmful bacteria The energy is similar UVL and does not make the food radioactive Fermentation It is the breakdown of carbohydrates material by microorganisms or under anaerobic conditions Several end products of fermentation particularly acids and alcohol ,inhibitory to the common pathogenic microorganisms that may find their way in the foods. Examples of food preserved through fermentation include: Cheese Butter Bread Alcoholic beverages etc Advantage /benefit of fermentation Flavor and textural changes Increase nutritional value Increase digestibility of food due to the breakdown of indigestible proactive coating of grains. Dehydration and drying It involves complete removal of H20 under controlled conditions in such a way that food quality is not altered. On reconstitution with h2o, dry foods are very close and visually indistinguishable from the original foods used in their preparation Foods could be dried naturally e.g. for cereals and grains They could also be dried through controlled methods e.g. by air convention driers ,drum
Types of freezing method Slow freezing /sharp- Foods are placed at the temperature ranging from -4 to -30 degrees Quick freezing- Lower temperature ranging from -32c to – 40c are used. Fine crystals are formed. This helps to protect the structure of foods on thawing. De-hydro freezing- Done in fruits and vegetables Foods dried about 50% of their original weight and volume then frozen to preserve it. The quality of fruits and vegetables does not change considerably. EFFECTS OF FREEZING FOOD Vitamin c and thiamine when vegetables are branched before freezing. Ascorbic acid is lost during storage if the temperature is much above -18degrees. Use of high temperatures for food preservation Most bacterial, yeast, mould and enzymes are destroyed by heating a food at around 100 oC. However, some are resistant and higher temperature for destruction are required./ Heat destroys microorganisms by denaturing their cellular proteins particulary the essential enzymes. Factors that influence type and intensity of heating process used in food preservation. Microbial load Microorganisms resistance to heating process The composition of food i.e. natural ph, acidify or a alkalinity Canning Involves the application of temp to food that are high enough to destroy essentially al microorganisms present contamination.Degree of heat and length of time of heating vary with the type of food and kinds of microorganisms targeted.Most fans are made of tin coiated steel or glass..Acid foods e.g. Tomatoes and fruit juices are easily processed than low acid foods because acids aid destruction of micro-organisms by heat.Acid foods can be processed safely if their internal temp reaches 82.2oc
scuss effects of preservation on nutritive value of foods. Nutritive value of canned foods In caned meat, thymine is lost if stored at 18 oc or higher. Ascorbic acid is well retained in citrus juices due to greater acidity. Thiamine is preserved in vegetables e.g tomatoes because they require minimum amount of heat due to their low PH. Pasteurization It is mostly used in liquids like milk and beer. Pasteurization is a heat treatment that kills part but not all microorganisms present and usually involves the application of temp below 100oc.It has to primary objectives:- I.e. to kill pathogenic microorganisms and inactivate enzymes Milk is the most pa5steurized food product by high temperature short time method. Dry fruits like raizings, dates can also be pasteurized in their package. Hurdle technology Is a method of ensuring that pathogens in food products are eliminated by combining more than one approach. These approaches can be thought of “hurdles” the pathogen has to overcome if it is to remain active in the food. The right combination of hurdles can ensure all pathogens are eliminated or render harmless in the final product. It also ensures stability , organytic and nutritional quality and the economic viability of food products. Hurdles used depends on the target pathogens. Smoking Increased shelf life is achieved by exposing food to smoke from burning plant materials such as wood.It is done on food product such as meat , fish etc that have undergone curing. Selected wood enhances flavor and presence of heat reduces h 2 o content in the food. Heat can also help to kill some bacteria present. Revision questions
- Define food preservation , asepsis, fermentation, canning, preservatives
- Explain the principles of food preservation
- Discuss various methods of food preservation
- Briefly di
