Cookery Rules And Preservation Of Nutrients
Question 1. Food preservation.
Answer.
Food preservation is the science dealing with the process of dealing with the prevention of decay or spoilage of food, thus allowing it to be stored in a fit condition for future use. The process used may be varied with the period of storage. It may be as simple as boiling milk to preserve it for 24 hours or pickling vegetables, fish or meat to last for a year.
Need for Food Preservation
There is always a shortage of food in developing countries like India due to demands of the growing population. Increasing production to meet the shortage results in wastage due to inadequate facilities available for storage and preservation. It is therefore all the more important to improve and expand facilities for storage and preservation of food. Preservation increases availability of foods, thus improving the nutrition of the people. Availability of seasonal foods throughout the year also helps in stabilising prices of food stuffs.
Principles Of Food Preservation
- Prevention or delay of microbial decomposition by
- Keeping out micro-organisms (asepsis).
- Removal of micro-organism, e.g. by filtration.
- Inhibiting the growth and activity of microbes by the use of lower temperature, drying, anaerobic conditions or chemicals.
- Destroying the microorganisms by radiation or by heat.
- Preventing or delay of self decomposition of the food by
- Destroying or inactivation of food enzymes e.g., by blanching or boiling.
- Prevention or delay of purely chemical reactions e.g. prevention of oxidation by antioxidants.
- Prevention of damage by insects and rodents.
Question 2. Methods Of Food Preservation.
Answer.
Methods Of Food Preservation
- Bacteriostatic Methods
Which inhibit the growth and multiplication of micro-organisms in food e.g., Freezing, dehydration, pickling, salting and smoking. - Bactericidal Methods
In which the microorganisms are killed, e.g., cooking, canning and irradiation.- Cold Storage and Freezing
Refrigeration is widely used both in homes and in commercial plants as a means of maintaining the low temperature necessary for storage of perishable foods. Micro-organisms are much less active at low temperature even though they may not be destroyed by severe cold. Fresh milk, and fish are kept just above the freezing point.
A refrigerator thermometer is kept in the refrigerator at all times. Left over foods from a meal should not stay out of refrigeration longer than two hours. Certain fruits and vegetables also keep better when cold. - Boiling
Boiling food at 100°C kills all vegetative cells and spores of moulds and yeast but not bacterial spores. Cooking of rice, vegetables, meat etc. is usually done in homes by boiling. Many foods are preserved at home by boiling e.g., Milk. Cooked food can be preserved from 12 to 24 hours at room temperature. - Canning
If the effectiveness of pasteurization and sterilization has to last for a long time, the material thus treated must be protected from fresh contamination by canning. Various foods eg. Fruit juices,milk, baby foods, soups and fish are preserved by canning. The food is first sterilized at temperature above 100°C for a few seconds and then cooked and filled in presterilised containers in a sterile atmosphere. There is some loss of heat labile vitamins during the process of canning. - Addition of Salt or Sugar
Certain chemicals are useful in preserving food, either by retarding or preventing the growth of microorganisms. There may be either added to the product or produced in it by fermentation. Dry salting is used for the preservation of tamarind, raw mango, amla, fish and meat. Pickling of mango, lemon, fish and meat is by addition of 15 to 20% salt. Rosagulla and gulabjamoon are preserved by sugar syrup. The principle is high osmotic pressure produced by salt or sugar.
- Cold Storage and Freezing
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- Jams and Marmalades
Jams and marmalades are prepared by boiling the fruit pulp or shredded fruit peels with sugar (above 55% by weight) to a thick consistency, firm enough to hold the fruit tissues in position. Later on, they are packed hot into glass jars or tin cans and sealed. The same process is used for jellies except that fruit juices are used in place of fruit pulps. The high concentration ofsugar (68%) binds the moisture making it not available for microorganism to grow and multiply. Anaerobic conditions are obtained by sealing. Application of heat kills most of the moulds and yeast. All these increase the shell life of the products. - pH
Low pH inhibits the growth of many organisms. Vinegar used in pickling is acetric acid. Citric acid is added to many fruit squashes, jams and jellies to increase acidity and to prevent mould growth. Formation of curd from milk is an example of lactic acid produced from lactose. The lactic acid inhibits the growth of bacteria. By adding certain condiments along with salt, certain foods like mangoes, vegetables, meat and fish are preserved.
- Jams and Marmalades
- Chemical Preservation
Benzoic acid is used to preserve fruits, fruit juices, squash and jams because it is soluble in water and easily mixes up with food products. Potassium metabisulphite or sodium metabisulphite is used to preserve colourless food stuff such as fruits, juices and squash. These preservatives, on reaction with fruit acids liberate SO2 (sulphur dioxide) which is quite effective in killing the harmful microbes present in food. SO2 is a bleaching agent and cannot be used as a preservative for coloured food materials.
Question 3.Prevention of food adulteration act, 1954.
Answer.
Prevention of Food Adulteration Act 1954 (PFA) The prevention of food adulteration act 1954 came into effect from june 1, 1955. The purpose of the Act is to ensure that food articles sold to the consumers are pure and wholesome, also to prevent deception or fraud and to ensure fair trade practices. The act was amended in 1964 and 1976 to plug the loopholes and to ensure deterant punishment to the offenders. As per the Act, food can be considered adulterated when any one of the following modes (or acts) are resorted to:
- Admixture of inferior or cheaper substance.
- Extraction of certain quality ingredients from the food.
- Preparing or packing under insanitary conditions.
- Sale of insect infected food.
- Obtaining the food from a diseased animal.
- Incorporation of a poisonous component.
- Entry of injurious constituents from the container used.
- Use of colouring matter other than or in greater quantities than that approved for the food.
- Sale of substandard products which may or may not be injurious to health. These are all prohibited acts under the prevention of Food adulteration act. Persons found guilty of selling such adulterated food, can be convicted. The severity of sentence would depend on the gravity of the offence.
Question 4. Food fortification.
Answer.
Food fortification or enrichment is the process of adding micronutrients (essential trace elements and vitamins) to food. It can be carried out by food manufacturers, or by governments as a public health policy which aims to reduce the number of people with dietary deficiencies within a population. The predominant diet within a region can lack particular nutrients due to the local soil or from inherent deficiencies within the staple foods; addition of micronutrients to staples and condiments can prevent large-scale deficiency diseases in these cases.
As defined by the World Health Organization (WHO) and the Food and Agricultural Organization of the United Nations (FAO), fortification refers to “the practice of deliberately increasing the content of an essential micronutrient, ie. vitamins and minerals (including trace elements) in a food, so as to improve the nutritional quality of the food supply and to provide a public health benefit with minimal risk to health”, whereas enrichment is defined as “synonymous with fortification and refers to the addition of micronutrients to a food which are lost during processing”.
Examples of fortification in foods.
Many foods and beverages worldwide have been fortified, whether a voluntary action by the product developers or by law.
The Food Fortification Initiative lists all countries in the world that conduct fortification programs, and within each country, what nutrients are added to which foods, and whether those programs are voluntary or mandatory. Vitamin fortification programs exist in one or more countries for folate, niacin, riboflavin, thiamin, vitamin A, vitamin B6, vitamin B12, vitamin D and vitamin E. Mineral fortification programs include calcium, fluoride, iodine, iron, selenium and zinc.
Question 6. Food additives.
Answer.
Food additives are substances added to food to preserve flavor or enhance its taste, appearance, or other qualities. Some additives have been used for centuries; for example, preserving food by pickling (with vinegar), salting, as with bacon, preserving sweets or using sulfur dioxide as with wines. With the advent of processed foods in the second half of the twentieth century, many more additives have been introduced, of both natural and artificial origin. Food additives also include substances that may be introduced to food indirectly (called “indirect additives”) in the manufacturing process, through packaging, or during storage or transport.
Categories
Food additives can be divided into several groups, although there is some overlap because some additives exert more than one effect. For example, salt is both a preservative as well as a flavor.
Food coloring.
Colorings are added to food to replace colors lost during preparation or to make food look more attractive.
Fortifying agents.
Vitamins, minerals, and dietary supplements to increase the nutritional value
Color retention agents.
In contrast to colorings, color retention agents are used to preserve a food’s existing color.
Emulsifiers.
Emulsifiers allow water and oils to remain mixed together in an emulsion, as in mayonnaise, ice cream, and homogenized milk.
Flavors.
Flavors are additives that give food a particular taste or smell, and may be derived from natural ingredients or created artificially.
Flavor enhancers.
Flavor enhancers enhance a food’s existing flavors. A popular example is monosodium glutamate. Some flavor enhancers have their own flavors that are independent of the food.
Question 7. Methods of cooking.
Answer.
Cooking Media Food can be cooked in various media or no media at all. Air, water, steam and fat or their combinations are used as cooking media. Food can be cooked by a combination of media e.g., Upma and halwa involve the combination of fat and water. Cooking in Air Grilling, roasting and baking take place in air. Roasting and baking are essentially the same. The term roasting is used to meat cooking and baking is used for breads, buns, cakes and biscuits. Food is cooked partially in dry heat and partially in moist heat. Cooking in Water Boiling or simmering involves cooking in water. The medium transferring heat is water.
- Roasting.
- Split roasting: Is done only with good quality meats. The food is brought in contact with direct flame in front of a bright fire. The food is pasted over with fat and is turned regularly to ensure even cooking and browning. Roast meats have an excellent flavour and are served in large hotels and special restaurants e.g., Barbe eued meat.
- Oven roasting: This is done in a closed oven with the aid of fat. First class meat, poulty and vegetables are put into a fairly hot oven for 5 to 10 minutes and temperature is lowered to allow the joint to be cooked. Cooking in a moderate oven for a longer time produces a better cooked joint than cooking at a higher temperature for shorter period. Aluminium foil is used. The joint is larded or raised with fat. This cooking is an improvement on oven roasting as the meat retains its moisture and flavour.
- Pot roasting: This is for cooking small joint and boils when no oven is available. A thick heavy pan is available and enough fatis melted to cover the bottom of the pan. The joint is browned when the fat is hot. The joint is then placed on a couple of skewers to prevent the joint from sticking to the pan. The pan is then covered tightly with the lid and cooked over a very low fire.
- Baking
Bread, cakes, pastries, puddings, potatoes and vegetables are cooked by baking. The food is surrounded by hot air in a closed oven. The action of the dry heat is modified by steam arising the food being cooked. - Frying
Here the food is brought in contact with hot fat. Even though fried foods are a bit difficult to digest, if the frying is carefully carried out, the fried food is suitable for normal people. Frying provides variety, keeping quality is better and the food is really apetising. - Boiling
Food is cooked by surrounding it by boiling or simmering liquid (stock or water). Only sufficient amount of liquid should be used just to cover the items to be cooked. Vegetables grown above the ground are cooked in boiled salted water and vegetables grown below the ground are cooked in cold salted water. Dry vegetables are cooked in cold water. Salt is added only after the vegetables become soft. Fish is put into hot liquid and allowed to simmer. - Poaching
Poaching is cooking slowly in a minimum amount of liquid which is not allowed to boil but kept below boiling point. Fish, eggs and fruits are poached. When poaching eggs, a little vinegar is added to the liquid for quick coagulation and to prevent disintegration. - Microwave Cooking
Microwave is electromagnetic radiation similar to that found in radio, radar or TV. Microwaves penetrate the food and are absorbed. The heating is very fast. Foods placed in the microwave oven are heated by microwaves from all the directions. This helps in easy cooking. - Pressure Cooking
Steam cooking are of three types—Steam cooking, waterless cooking and pressure cooking. In steaming, food is cooked by steam from added water. In waterless cooking the steam originates from food itself. Pressure cooking is a device to reduce the cooking time by increasing the pressure so that the boiling point is quickly reached. The food is cooked as a result of steam condensation on food e.g., rice, dal, puttu.
Question 8. Principals of Weaning.
Answer.
Weaning is the process of gradually introducing an infant human or another mammal to what will be its adult diet while withdrawing the supply of its mother’s milk.
The process takes place only in mammals, as only mammals produce milk. The infant is considered to be fully weaned once it is no longer fed any breast milk.
Basic principles
The basic principles of baby-led weaning are:
- At the start of the process the baby is allowed to reject food, and it may be offered again at a later date.
- The child is allowed to decide how much it wants to eat. No “fill-ups” are to be offered at the end of the meal with a spoon.
- The meals should not be hurried.
- Sips of water are offered with meals.
- Initially, soft fruits and vegetables are given. Harder foods are lightly cooked to make them soft enough to chew on even with bare gums.
- Food given is free of added salt and sugar.
- Food is not cut into bite-sized pieces until the baby has mastered object permanence and the pincer grasp.
- Initially, food is offered in baton-shaped pieces or in natural shapes that have a ‘handle’ (such as broccoli florets), so that the baby can get a good grip and the food is visible for babies that have not yet mastered object permanence.
- Foods with clear danger, such as peanuts, are not offered.
- Foods can be offered to the baby on a spoon, but the baby is allowed to grab the spoon and the adult helps the baby guide it to the mouth.
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