AESTHETIC AND SCIENTIFIC PRINCIPLES IN SELECTION AND STORAGE OF FOOD
SUBMITTED
OBAFEMI AWOLOWO UNIVERSITY ILE IFE
NOVEMBER 2010
The Principles of Food Selection
When making food choices, we need to follow a basic guiding principle: Food imparts nourishment in multiple ways. Understanding and using nutrition to enhance well-being is nothing new – our ancestors practiced this for thousands of years.
Grasping this wisdom enables us to select food that will encourage a healthy metabolic process. Below is an overview to help you select your food.
1. Whole Foods: Favoring whole, intact foods supports optimum health. Thus, food should be consumed whole – all the edible parts of the food should be used. Whole foods have only one ingredient – themselves. For example, favor eating an orange rather than drinking the juice, and choose whole grain breads instead of enriched flour breads. This will ensure that you are consuming all of the nutrients in the right amount or combination.
2. Fresh Natural Foods: Food should be as fresh and natural as possible. Choose foods that are closest to their natural state – not processed, canned or frozen. While food that has been canned or frozen lasts a long time, it can lose from 20 to 80% of its nutrients. Try to eat fresh as often as possible, but if it is not available, choose dried, pickled or fermented food. Avoid commercially deep fried foods.
3. Organic Foods: Choose organic foods whenever you can. Chemically grown food burdens the kidney and liver (which filter chemicals) as well as our environment. If your budget does not allow for all organic, prioritize organic meat, dairy, oils, nuts, seeds and grains.
4. Seasonal and Local Foods: Try to eat seasonal, regional produce as much as possible. This increases the likelihood that your food will be fresh, ripe, preservative-free and nutrient-rich. Eating seasonally means choosing “summer vegetables” during summer months (tomatoes, zucchini, corn ) – their thermal properties will keep you cool in the heat. Favor heartier produce in cooler months, like dark green leafy vegetables (kale, Swiss chard, collard greens), root vegetables (sweet potatoes, parsnips, yams), and fruit (apples, pears), which can help you stay warm in colder temperatures. Buying local food makes sense for a number of reasons: it has fewer preservatives, it supports your local farmers and it’s gentler on the environment. From an energetic point of view, it also makes sense: local food will help you stay balanced and in tune with your specific environment.
5. Real Foods: Always eat real foods. There are many “food like” products in the market place that try to imitate the real thing, such as artificial sweeteners, artificial color, and artificial flavors. Try to eliminate them from your diet.
6. Balanced Meals: Each meal should include all your macro-nutrients (carbohydrates, proteins and fats) and micro-nutrients (vitamins and minerals). As a simple rule of thumb, try to eat colorful food. You can get all of your vitamins and minerals by consuming colorful fruits and vegetables, and your macro-nutrients by consuming whole grains and good fats (such as olive oil). Also, try to include a good quality protein, such as beans or fish.
7. Traditional Foods: Our bodies are better suited to digesting and using the foods eaten for centuries by our ancestors. When you eat the beans and grains that were the traditional foods of your ancestors from the “old country,” you keep the tradition alive and nourish yourself more richly. Answer this basic question: what grains and beans did your ancestors eat? Native Americans would answer corn, peas, and pinto beans. Northern Europeans would answer rye, barley, buckwheat and white beans. South Americans would answer quinoa and black beans. Asians would answer soy and rice.
8. Delicious Foods: Following these principles, you are bound to prepare and enjoy delicious food, but do not feed yourself with too many food facts and figures. Yes, you can educate yourself about what your body requires nutritionally, but ultimately the real test is how your body responds to it, so feed yourself with good, delicious food, and be mindful of how the food makes you feel.
PRINCIPLES OF FOOD STORAGE
Storage definition: The process in which both cooked and raw materials are stored in appropriate conditions for future use without any entry or multiplication of micro-organisms.
Types of food
· Uncooked: vegetables, meat, fish, poultry, eggs, fruits, dairy products
· Cooked: Gravies, rice etc
· Tinned products: purees, pickles etc
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Major storage areas for Stock holding
1) Dry food store for non perishables (short holding time)10` to 21` c
2) Refrigerated store for perishables (short holding time)1` to 4` c
3) Freezer store for perishables (long holding time) -6` to -25` c
Basic guidelines for food storage
1) Wash items that need washing, cans to be wiped
2) Frozen items to be solidly frozen
3) Rotation of stock, fifo (first in first out, first manufactured, first used)
4) Each storage area to be separate from each other
5) Cut food items to be always covered
6) Storage area to be cleaned regularly
7) Access for storage area to be restricted to prevent pilferage
8) Maintaining appropriate temperatures depending on type of food being stored
9) Over crowding & over stocking of storage area blocks air circulation making the food to spoil fast
10) Any kind of cross contamination to be avoided
1.0 SCIENTIFIC PRINCIPLES IN STORING FOOD
The term food preservation refers to any one of a number of techniques used to prevent food from spoiling. It includes methods such as canning, pickling, drying and freeze-drying, irradiation, pasteurization, smoking, and the addition of chemical additives. Food preservation has become an increasingly important component of the food industry as fewer people eat foods produced on their own lands, and as consumers expect to be able to purchase and consume foods that are "out of season."
(1)Smoking
The process of smoking is a sophisticated method of food preservation with both hot and cold forms in use. Hot smoking is used primarily with fresh or frozen foods, while cold smoking is used most often with salted products. The most advantageous conditions for each kind of smoking—air velocity, relative humidity, length of exposure, and salt content, for example–are now generally understood and applied during the smoking process. For example, electrostatic precipitators can be employed to attract smoke particles and improve the penetration of the particles into meat or fish.
So many alternative forms of preservation are now available that smoking no longer holds the position of importance it once did with ancient peoples. More frequently the process is used to add interesting and distinctive flavors to foods.
(2)Drying
Since most disease-causing organisms require a moist environment in which to survive and multiply, drying is a natural technique for preventing spoilage. Indeed, the act of simply leaving foods out in the sun and wind to dry out is probably one of the earliest forms of food preservation. Evidence for the drying of meats, fish, fruits, and vegetables go back to the earliest recorded human history.
Today, a host of dehydrating techniques are known and used. The specific technique adopted depends on the properties of the food being preserved. For example, a traditional method for preserving rice is to allow it to dry naturally in the fields or on drying racks in barns for about two weeks. After this period of time, the native rice is threshed and then dried again by allowing it to sit on straw mats in the sun for about three days.
Modern drying techniques make use of fans and heaters in controlled environments. Such methods avoid the uncertainties that arise from leaving crops in the field to dry under natural conditions. Controlled temperature air drying is especially popular for the preservation of grains such as maize, barley, and cowpea,
Vacuum drying is a form of preservation in which a food is placed in a large container from which air is removed. Water vapour pressure within the food is greater than that outside of it, and water evaporates more quickly from the food than in a normal atmosphere. Vacuum drying is biologically desirable since some enzymes that cause oxidation of foods become active during normal air drying. These enzymes do not appear to be as active under vacuum drying conditions, however.Two of the special advantages of vacuum drying is that
· the process is more efficient at removing water from a food product, and
· it takes place more quickly than air drying. In one study, for example, the drying time of a fish fillet was reduced from about 16 hours by air drying to six hours as a result of vacuum drying.
Freeze-drying is a method of preservation that makes use of the physical principle known as sublimation. Sublimation is the process by which a solid passes directly to the gaseous phase without first melting. Freeze-drying is a desirable way of preserving food since it takes place at very low temperatures (commonly around 14°F to -13°F [-10°C to -25°C]) at which chemical reactions take place very slowly and pathogens survive only poorly. The food to be preserved by this method is first frozen and then placed into a vacuum chamber. Water in the food first freezes and then sublimes, leaving a moisture content in the final product of as low as 0.5%.
(3)Salting
The precise mechanism by which salting preserves food is not entirely understood. It is known that salt binds with water molecules and thus acts as a dehydrating agent in foods. A high level of salinity may also impair the conditions under which pathogens can survive. In any case, the value of adding salt to foods for preservation has been well known for centuries.
Sugar appears to have effects similar to those of salt in preventing spoilage of food. The use of either compound (and of certain other natural materials) is known as curing. A desirable side effect of using salt or sugar as a food preservative is, of course, the pleasant flavor each compound adds to the final product.
Curing can be accomplished in a variety of ways. Meats can be submerged in a salt solution known as brine, for example, or the salt can be rubbed on the meat by hand. The injection of salt solutions into meats has also become popular. Food scientists have now learnt that a number of factors relating to the food product and to the preservative conditions affect the efficiency of curing. Some of the food factors include
· the type of food being preserved,
· the size of treated pieces.
Preservative factors include
· brine temperature and
· the presence of impurities.
Curing is used with certain fruits and vegetables, such as cabbage (in the making of sauerkraut), cucumbers (in the making of pickles), and olives. It is probably most popular, however, in the preservation of meats and fish. Honey-cured hams, bacon, and corned beef ("corn" is a term for a form of salt crystals) are common examples.
(4)Freezing
Freezing is an effective form of food preservation because the pathogens that cause food spoilage are killed or do not grow very rapidly at reduced temperatures. The process is less effective in food preservation compared to thermal techniques such as boiling because pathogens are more likely to be able to survive cold temperatures than hot temperatures. In fact, one of the problems surrounding the use of freezing as a method of food preservation is the danger that pathogens deactivated (but not killed) by the process will once again become active when the frozen food thaws.
A number of factors are involved in the selection of the best approach to the freezing of foods, including
· the temperature to be used,
· the actual method used to freeze the food
Because of differences in cellular composition, foods actually begin to freeze at different temperatures ranging from about 31°F (-0.6°C) for some kinds of fish to 19°F (-7°C) for some kinds of fruits.
The rate at which food is frozen is also a factor, primarily because of aesthetic reasons. The more slowly food is frozen, the larger the ice crystals that are formed. Large ice crystals have the tendency to cause rupture of cells and the destruction of texture in meats, fish, vegetables, and fruits. In order to deal with this problem, the technique of quick-freezing has been developed. In quick-freezing, a food is cooled to or below its freezing point as quickly as possible. The product thus obtained, when thawed, tends to have a firm, more natural texture than is the case with most slow-frozen foods.
About half a dozen methods for the freezing of foods have been developed. One, described as the plate, or contact, freezing technique, was invented by the American inventor Charles Birdseye in 1929. In this method, food to be frozen is placed on a refrigerated plate and cooled to a temperature less than its freezing point. Or, the food may be placed between two parallel refrigerated plates and frozen.
Another technique for freezing foods is by immersion in very cold liquids. At one time, sodium chloride brine solutions were widely used for this purpose. A 10% brine solution, for example, has a freezing point of about 21°F (-6°C), well within the desired freezing range for many foods. More recently, liquid nitrogen has been used for immersion freezing. The temperature of liquid nitrogen is about -320°F (-195.5°C), so that foods immersed in this substance freeze very quickly.
As with most methods of food preservation, freezing works better with some foods than with others. Fish, meat, poultry, and citrus fruit juices (such as frozen orange juice concentrate) are among the foods most commonly preserved by this method.
(5)Fermentation
Fermentation is a naturally occurring chemical reaction by which a natural food is converted into another form by pathogens. It is a process in which food "goes bad," but results in the formation of an edible product. Perhaps the best example of such a food is cheese. Fresh milk does not remain in edible condition for a very long period of time. Its pH is such that harmful pathogens begin to grow in it very rapidly. Early humans discovered, however, that the spoilage of milk can be controlled in such a way as to produce a new product, cheese. Cocoa is another example
Bread is another food product made by the process of fermentation. Flour, water, sugar, milk, and other raw materials are mixed together with yeasts and then baked. The addition of yeasts brings about the fermentation of sugars present in the mixture, resulting in the formation of a product that will remain edible much longer than will the original raw materials used in the bread-making process.
