1. FOOD TECHNOLOGY
Foods 4 - 5

2. food PRESERVATION
Microorganisms need food, warmth, moisture and time to multiply. If one these conditions is removed, the food is preserved and will keep for a longer time. If microorganisms and enzymes are destroyed or a chemical added (preservative) this also allows food to last longer.
Limitations:
Can sometimes be more expensive.
Often contain a lot of fat, sugar, and salt.
Do not contain much fibre (except for canned baked beans and sweet corn).
Some nutrients have been lost when the food was processed.
Texture of food may change, for example, canned strawberries are much softer than fresh strawberries.
Additives may need to be added to restore color flavor, and texture.

3. The Benefits of Preserving food
Prevents microorganisms from multiplying
May provide a skill that the family caterer does not have
Can buy products that are not in season
Lasts longer, therefore fewer shopping trips
Increased shelf life
Increases the range of food available
Prevents the action of enzymes
Can save time, effort, fuel and there is less waste e.g. ready meals (cook-chill microwave meals)

4. Food is preserved in many ways so that it keeps longer.
HIGH TEMPERATURE METHODS
A. Pasteurization
Pathogenic microorganisms are destroyed. The food is heated to 72C for
15 seconds.
Storage of food is extended for a limited time – days not months.
Used for heat-treating milk, some soups, liquid egg and ice cream

5. Sterilization
Food is heated for a long period of time at higher temperatures. Heated to 104C for 40 minutes.
Destroys nearly all microorganisms and enzymes.
Extends storage period.
Used for milk and fruit juices.
Milk is changed to a creamy color, with a slight caramelization of the milk sugar content, giving a “cooked” flavor

6. C. Ultra Heat Treatment (UHT)
Uses very high temperatures, up to 130C for 1-5 seconds. Destroys all bacteria.
Extends storage period of milk, up to six months unopened.
Little color change.
Only slight change in taste.
Little loss of nutrient content
Sold in air-tight cartons, for example, soups, prepared sauces, such as chili.

7. CANNING It is a form of sterilization. Food can be:
Packed in cans and then sterilized
Sterilized and then packed into aseptic (sterilized) cans.
The cans re then sealed with a double seam to prevent leakage and to prevent recontamination. Temperature and time vary depending on the food type, but it is crucial to ensure that the sterilization process is complete and that the food retains its structure and texture. After sterilization the cans are sprayed with water to prevent overcooking the contents.

8. Canning is used for a huge range of foods like soups, vegetables, fruit, meat and fish to give a long shelf life.
The texture of some foods may change for example strawberries become soft.
There is some loss of nutrients especially vitamins B and C.
Acid foods, like grapefruit are canned in plastic-lined cans to prevent corrosion.

9. LOW TEMPERATURE METHODS
bacterial growth is slowed down when the temperature is lowered, and at -18C bacteria become dormant.
Chilling and freezing in industry
1. Cook-chill – food that has been cooked, fast-chilled in 1 ½ hours and stored at low temperature
It is a short term way of preserving fresh food
Correct temperature controls are followed at all stages of manufacture, storage, and distribution in order to
have records of temperature control
prevent waste
avoid bacterial growth
avoid complaints
meet the requirements of the Food Safety regulations
keep food at its best (texture/color/taste/appearance)

10. Advantages of Cook-Chill
very little change in nutritional value, flavor, color, texture or shape
fresh foods can be kept at maximum quality for a longer time
the consumer can be offered a much larger range of fresh and convenience foods
nutrients are not destroyed
no need to defrost as in frozen products, therefore quicker to cook/reheat
fewer additives needed during manufacture
available in single portion
no skill required – easy to prepare or cook, little equipment or washing up
consistent quality
little waste
saves energy in the home

11. Example of cook-chill foods:
A single raw food for example meat, fish
A mixture of raw foods, for example, coleslaw, stir-fry vegetable, mixed lettuce leaves
Made from cooked ingredients for example recipe meals such as lasagna, soup
A mixture of both raw and cooked foods like potato salad.

12. Blast – freezing
This method can is suitable for most foods.
It is a quick-freezing method; small ice crystals form and there is less damage to the food in slow freezing.
Complete meals can also be frozen, provided their maximum thickness is no greater than 4 cm.
Air is circulated around a freezing compartment by a fan, reducing the temperature of the food quickly.
Food must be kept in storage units at a temperature of between -20c and -30C after freezing.
Freezing is rapid so the texture of soft tissue is unchanged.
This is not a widely used method because it is expensive.
Vacuum chilling is now being used instead of blast-freezing because it is a quicker method of cooling.

13. Cryogenic freezing
It is used for delicate products and fruits, such as raspberries and meringue desserts. The foods are immersed in or sprayed with liquid nitrogen.
Cook-freeze
Meals are blast-frozen and stored at -20C until required. Dishes must be prepared with strict attention to hygiene.
The food can be distributed to branch outlets in the frozen state and heated by microwave or micro-ovens when required for service.
Advantages:
Gives the consumer more choice
Handy in emergencies
Consumer demands
Extends shelf-life
Keeps up with competitors
Saves time

14. Dehydration (drying) Chemicals
It is the removal of water from food. There are various methods of using drying to preserve food. Dried foods are cheaper and easy to transport and store. They have a relative long shelf life if stored in protective packaging. The flavor, color, texture and nutritional value of dried foods are affected. They lose vitamin C.
Chemicals
Chemical preservation destroys bacteria or prevents them from reproducing . The chemicals work by affecting the growth of microorganisms. Chemicals used for preserving food include the following
Vinegar
Acetic acid with low pH of 3.5 (bacteria cannot survive below 4.5)
Used for foods such as pickled onion, cabbage, and eggs.

15. B. Salt
Used to coat foods such as ham, bacon, and fish, or used in a brine solution (salt and water), such as for tuna and vegetable.
Reduces moisture content by osmosis.
Sugar
In high concentrations (60% of final product) it prevents bacteria from growing because it makes the water unavailable.
Used in jams, jellies, marmalades.
Strong sugar solutions can also be used for coating candied and crystallized fruit.

16. Physical Methods of preserving foods
Physical means of preserving foods include vacuum packing, smoking, modified atmosphere packing (MAP) and irradiation.
Modified Atmosphere Packaging (MAP)
Involves changing the atmosphere around the food inside some packaging so that growth of microorganisms is slowed down, so that the product can last longer. Altering the gas in the packet prevents bacteria to use the oxygen for growth, which means the product has an increased shelf life. The advantage is that you can see the product. It is used for chilled meats, vegetables and fruits.

17. The MAP process involves:
Packaging fresh foods in peak condition; the color of the food remains the same until the pack is opened, and once opened the food has a normal shelf life.
Replacing the air by “gas-flushing” a combination of gases around the food; gases used are oxygen, nitrogen and carbon dioxide.
Sealing the plastic bag or plastic lid to a food tray by means of hermetic sealing process.
Vacuum Packing
This is done by removing air and sealing the package. It also prevents bacteria growing . Once opened it has normal shelf life.
The food is kept in anaerobic conditions.
Foods maintain color and texture.
Coffee, once accelerated freeze-dried (AFD), is vacuum packed so that it does not lose taste or flavor.

18. Irradiation
This process uses radiation to fire gamma rays into food. This kills pests, insects and some microorganisms. It is used to stop onions and potatoes sprouting, and to kill insects, in spices, fruits, and vegetables. It is not popular in the UK and many supermarkets refuse to sell irradiated foods.
Irradiation is known as a cold process. It does not significantly increase the temperature or change the physical or sensory characteristics of most foods. An irradiated apple, for example, will still be crisp and juicy. Fresh or frozen meat can be irradiated without cooking it. During irradiation, the energy waves affect unwanted organisms but are not retained in the food. Similarly, food cooked in a microwave oven, or teeth and bones that have been X-rayed do not retain those energy waves.