Physic-chemical properties �Food enzymes �Food additives

Physic-chemical properties �Food enzymes �Food additives

1. Physic-chemical properties Food enzymes Food additives Prof. Dr. Nanis Gomah

2. Hydrogen-ion concentration The term pH is the symbol for hydrogen-ion concentration which is used to express the degree of acidity or alkalinity of a food or a given solution. The hydrogen-ion concentration of a food is a controlling factor in regulating many chemical and microbiological reactions. The pH is the negative logarithm to the base to the hydrogen-ion concentration . The pH or buffering action is very important in foods.

3. It is evident that the acidity and alkalinity of foods are of great importance in food processing. Some foods, e.g. fruits, contain organic acids and have an acid reaction , whereas foods such as milk and eggs have a neutral reaction. For example, when milk is kept exposed for a long time, it curdles while being heated due to development of acidity in milk . Similarly, when lemon juice is added to milk , the protein (casein) present in milk precipitates along with fat. Milk contains several salts such as potassium and sodium phosphates which are responsible for its stability . Hence acidity and alkalinity of foods are of general importance in food processing.

4. Hydrogen ion concentration has to be contained within narrow limits to co-ordinate various biological activities in an aqueous system . It is important for proteins to have stable, ‘native’ structure which is highly dependent on pH. For example, the catalytic activities of enzymes are drastically altered on moderate changes in pH. Lactic acid production in muscle , an enzymatic process, falls by 37% when H+ concentration increases from 40 n mol / litre (pH 7.4) to 85 (pH 7.1). Blood plasma pH which is fair reflection of intracellular pH, is maintained within very narrow limits (7.35-7.45). When blood pH goes above 7.8 tetany occurs. Conversely, excessive acidity (pH less than 7.0) results in coma .

5. The enzymes Enzymes are complex organic catalysts which catalyze biochemical reactions in the plant and animal cells . Enzymes cause many desirable changes in foods during processing . Some applications of enzymes in food processing :

6. Amylases Amylase is the best used enzyme in industry . Bacterial liquefying α -amylase is widely employed for liquefaction in starch processing for various purposes, mostly in conjunction with other amylases. Mold α-amylase is used in the baking industry, due to its heat instability. Mold glucoamylase is an important enzyme in the production of glucose and glucose syrup , and in alcohol fermentation . Plant and bacterial β-amylase is utilized in the production of maltose and maltose syrup .

7. Proteases Both proteases and peptidases are found in mature, sound cereals , however their levels of activity are relatively low . Several methods of determining proteolytic activity are based upon production of soluble cereal protein. Wheat flour appears to contain proteolytic enzyme with pH 4.1 that may be of importance in achieving fermentation of dough . The peptidases may be important in producing soluble organic nitrogen that is utilized by yeast during the fermentation. .

8. Lipases Although lipases are enzymes that split triglycerides , the building unit of oils and fats. All cereals have lipase activity , but the activity varies widely within cereal. Oats have high activity compared with that of wheat or barley . ( Why? ) Lipase activity is important because a free fatty acid is more susceptible to oxidative rancidity than is the same fatty acid in a triglyceride . Free fatty acids often give a soapy taste to the product which is undesirable and indicate a high acid value

9. PHYTASE Phytase is an esterase that hydrolyzes phytic acid. Phytic acid , which perhaps chelate divalent ions and prevent them from being absorbed in the intestinal tract . The enzyme converts it to inositol and free phosphoric acid. Thus the enzyme activity is important(why?) , as it converts the harmful phytic acid effect into inositol (vitamin) and nutrients .

10. Pectinases ( Pectic Enzymes) Pectic enzymes occur in higher plants and are synthesized by microorganisms . Their substrate is a variety of pectic substances which occur as structural polysaccharides in the cell-wall of higher plants. Native pectic enzymes can therefore produce important textural changes in fruits and vegetables during storage and processing operations. Microbial pectic enzymes are important in plant pathology ; they are also produced on a large scale as a processing aid for the food industry . Consistency changes during ripening and storage of fruit and vegetables are often linked to pectic changes which in turn can be ascribed to pectic enzymes

11. Food additives Food additives may be defined as non-nutritive substances added intentionally to food generally, in small quantities to improve its quality properties such as: 1-appearance 2-flavor 3-texture 4- storage ability. Need and wants of the consumer dictate the use of additives in industry.

12. Among food additives some are used to color foods , others to bleach them , some add flavor to food, others remove flavors , some make food firmer, others soften food, some keep foods dry , others keep moist , some thicken foods, others keep them from thickening , some produce foams , others prevent foams , sometimes one food additive has more than one function .

13. Broad classes of intentional food additives The intentional food additives may be classified under 12 broad groups preservatives; antioxidants; surface active agents ; stabilizers thickeners ; bleaching and maturing agents, starch modifiers ; buffers , acids and alkalis; food colors; non-nutritive and special dietary sweeteners; nutrient supplements; flavoring agents; .

14. Preservatives These include chemical preservatives against bacteria, yeasts, and molds. Sodium benzoate is used in soft drinks and acidic foods; sodium and calcium propionates in breads and cakes as a mold inhibitor ; sorbic acid on cheese ; and compounds of chlorine as a germicidal wash for fruits and vegetables Flavoring agents and flavor enhancers: The flavoring agents include both natural and synthetic flavors. Some of the natural flavoring substances include spices, herbs, essential oils and plant extracts . Typical of the synthetic flavor additives are benzaldehyde (cherry), ethyl butyrate (pineapple). Currently there are more than 1,200 different flavoring materials used in foods, due to the ever-increasing variety of different foods.

15. Non-nutritive dietary sweeteners The well-known substance is saccharin . Saccharin is permitted as a sweetener in food preparations and soft drinks for diabetic subjects . In 1972 FDA, USA, recommended that the daily intake of saccharin by an adult should not exceed 1 g , as the studies have shown that rats receiving saccharin developed bladder tumors. Nutrient supplements Principal among these are the vitamins and minerals added as supplements and enrichment mixtures to a number of products. Important examples are: vitamin D added to milk; B vitamins, iron and calcium added to cereal products; iodine to salt; vitamin A to margarine; cheeses made from bleached milks; dietary infant formulas; and vitamin C to fruit juices and fruit-flavored desserts.

16. Food colors Colors are added(why ) to many food items, to improve their appearance and to give the public appetizing and attractive qualities they desire . Colors from natural materials such as annatto, caramel, carotene and saffron are the best examples. Colors of synthetic origin which include coal tar dyes have been examined for their safety. Synthetic colors generally excel in: coloring power Uniformity stability lower cost . Carbonated beverages, candies, and gelatin desserts are among items colored with certified coal-tar dyes.

17. Safety of food additives Safety in using an additive is an important consideration. It is impossible to establish absolute proof of the non-toxicity of a specified use of an additive for all human beings under all conditions ; critically designed animal tests of the physiological, pharmacological and biochemical behavior of a proposed additive can provide a reasonable basis for evaluating the safety use of a food additive at a specified level of intake.

18. It is generally believed that the presence of harmful impurities in food additives can be most effectively excluded by establishing purity specifications . It is agreed that the amount of an authorized additive used in a food should be the minimum necessary to produce the desired effect . For all people, legal control over the use of food additives is essential . This is best accomplished through the use of a permitted list , which effectively prevents the addition of any new substances to food, until an adequate basis for judgement of their freedom from health hazard has been established

19. • As a matter of principle, food-label declaration informing the consumers of the presence of additives in the product, has been found to be the most effective method of achieving this result . • Regulations governing the control of food additives are useless, unless the laws can be enforced by: Trained food inspectors food-control laboratories reliable analytical methods are of utmost importance.

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