Methods of Food Preservation

Drying

The process of drying reduces the water content of food sufficiently to delay or prevent bacterial or fungal growth. The process of drying food can be done under the hot sun, over a fire or through modernised dehydration equipment. Most bacteria and fungi become inactive and stop growing when the surroundings are dry.

Food can be dried by:

a) Suspending food or placing food on racks in the Sun (sun drying)

b) Using food dehydrator, a smell electric appliance for drying foods indoors

c) Heating the food in an oven (oven drying)

Dried salmon Dried grapes

Dried chilly

Smoking

Smoking combines drying with chemical from the smoke, which forms a protective coat to slow down spoilage. Smoking not only dries food but also adds a preservative that changes the taste and enhances the flavour of the food. Smoking is done over charcoal or smokehouse.

Smoked banana smoked fish

Smoked chicken

Pasteurization

Pasteurization is the process of heating liquid with the purpose of destroying viruses and harmful organisms. It is named after scientist Louis Pasteur who used the application of heat to destroy microorganisms in food. Unlike sterilization, pasteurization is not intended to kill all microorganisms in the food, but to reduce their number so that they are unlikely to cause decay. Food can be pasteurised by heating it to 63 0C for 30 minutes or 72 0C for 15 seconds, followed by rapid cooling to below 10 0C. Pasteurised food can have a refrigerated shelf life to two to three weeks.

pasteurised milk pasteurised juice

ice-cream yoghurt

Freezing

Freezing is one of the most commonly used processes both commercially and domestically for preserving a very wide range of foodstuffs. This is because the very low temperature can retard and prevent the growth of microorganisms effectively. Freezing is keeping food in a freezer at a temperature of -15 0C. Freezing does not alter the texture, taste and nutritional value of the food. Frozen food can be kept fresh for months.

frozen food frozen meat

frozen fish frozen vegetables

Pickling

Pickling is soaking food or cooking it in a substance that inhibits the growth of microorganisms. Typical pickling agents include salt , vinegar and sugar. Acetic acid found in vinegar stops the growth of microorganisms. The presence of vinegar creates a high acidic condition. Pickled food can be kept food for years. However, its taste and nutrient content will be different.

The Pickling Process

pickled vegetables

Cut the fruit into pieces

Wash and rinse the fruit

Mix the fruit with salt

Soak the fruit into concentrated sugar solution

Add some vinegar

Seal the bottle tightly

Cooling

Food can be preserved by storing them in a cool place such as a refrigerator. In a cool condition, bacteria become inactive and do not reproduce or give off poisonous gases. Cooling is the most popular method of food preservation. Food can kept in the refrigerator at temperatures between 00C and 50C stays fresh for a longer time.

vegetables eggs

milk fruits

Boiling

Boiling food makes food sterile because the bacteria present have been killed by the heat. However, boiling affects the taste and nutritional value of the food.

cooked chicken boiled egg

INTRODUCTION

1. Our food comes from animals and plants.2. Fresh products such as fruits, milk and vegetables do not last long if kept at room temperature.3. Food turns bad because of bacteria and fungi. 4. However, not all bacteria and fungi are harmful.5. When food spoilt, it usually changes in appearance.

CHARACTERISTICS OF SPOIL FOOD

                      7. The growth of microorganisms such as fungi and bacteria can spoil food.8. Fungi and bacteria can grow on damp foods that are exposed to the air.9. Fungi and bacteria change the food material into simple substances.                        10. These simple substances may be poisonous.11. Spoilt food is unsafe to eat because it contains poisonous substance.12. We can get food poisoning if we eat spoilt food.

emit an unpleasant

smell

change colour

become mouldy

change in texture

become slimy

have an unpleasant

taste

13. Eating spoilt food can also cause bacterial and fungal infections.14. The conditions suitable for the growth of microorganisms are...

      15. Bacteria and fungi cannot grow if there is no air.16. Bacteria and fungi can grow easily in damp and warm conditions.17. Bacteria and fungi get killed at high temperatures.18. Bacteria and fungi cannot grow if there is no water.19. Bacteria and fungi cannot grow in a very acidic or very alkaline  solution.20. We can prevent food from going off or at least delay it.21. We must preserve it.22. We preserve food to make it last longer.23. Food preservation is a process of slowing down the decay of food.24. Food preservation is important because:   

it keeps food for a longer time.it kills bacteria and fungi

25. We preserve food by:

WATER

AIR

SUITABLE ACIDITY

SUITABLE TEMPERATURE

NUTRIENTS

  keeping it dry keeping it hot or frozen keeping it airtight

26. There are various methods of preserving food.

Vacuum-packing

METHODS OF PRESERVATION

DRYING

BOILING

COOLING

VACUUM PACKINGPICKLINGFREEZINGBOTTLING/

CANNINGPASTEURISATION

SALTING

SMOKING

WAXING

In this method of preservation, food is sterilised before it is packed in air-tight containers     or packages, depending on the type of food. Air from the packages and containers are drawn out to make a vacuum. Microorganisms cannot survive without air as they require air for respiration. Examples of food preserved by vacuum-packing are biscuits, peanuts, coffee powder and crackers. Examples of fruits that are preserved by vacuum-packing are bananas, pineapples and corn.

fruits vegetables

nuts chips

Bottling/canning

We can also preserve food by putting it in airtight cans or bottles. Food can keep very long if kept in airtight cans or bottles. The food is cooked before it is canned or bottled. The air within is removed before the container is sealed. Growth of bacteria and mould is prevented due to the lack or air. Foods that can be preserved by canning or bottling include meat, fish, fruits and vegetables. The Bottling Process 

 Salting

RinsingThe food is prepared and washed

BoilingFood is boiled to kill all the bacteria

SealingThe tins or jars filled with the boiled foodThe tins are heated to remove the air and sealed immediately

HeatingThe tins are heated under temperatures and pressure to make sure all bacteria are killed.

Labelling and packingThe tins are labelled and packed

We can preserve food by adding a large amount of salt to the food or soaking the food concentrated salt solution. This is called salting. Microorganisms such as bacteria and fungi cannot grow in very salty. In salty conditions the microorganisms will lose water and shrink. We can make this process more effective by drying the salted food. Examples of food that can be preserved by salting are vegetables, meat, fish and eggs. 

salted duck egg salted fish

salted vegetables

   

Waxing

We can preserve food by covering with wax. This process is called waxing. The wax is obtained from plants, beef fat and petroleum. Waxing help to slow down the loss of water from fruits and vegetables. Waxing also give a gloss to the skin and makes the fruits and vegetables more shiny. However, waxing can be harmful to humans. Even washing in hot water cannot remove the wax from the waxed food.

Fruits vegetables

Summary

Some foods such as fruits and vegetables are available in some season and not in others. Other foods are more abundantly available in some season than in others. So civilized men adopted techniques to preserve such seasonal foods intact for later use. Food preservation methods have been followed by men since times immemorial. Now modern technology has been widely introduced in this branch, by understanding the importance of such food processing methods in human life. Food production and supply does not always tally with the demand or meets of the people. In some places there is surplus production of a food product, whereas in some other place there is inadequate supply. Even foods are perishable and semi-perishable like juicy fruits, vegetables, mangoes, tomato, papaya and many more, which very quickly gets spoilt. It is therefore important to improve and expand facilities for storage and preservation of food. Food preservation helps in:

Increasing the self-life of foods thus increasing the supply. So many perishable foods can be preserved for a long time.

Making the seasonal food available throughout the year.

Adding variety to the diet.

Saving time by reducing preparation time and energy, as the food has already been partially processed.

Stabilising prices of food, as there is less scope of

shortage of supply to demand.

Decreasing wastage of food by preventing decay or spoilage of food.

Improving the nutrition of the population. Preserved foods help people to bring a variety in the diet, thereby decreasing nutritional inadequacies.

aCKNOWLEDGEMENT

Thanks to my teacher, Puan A.Letchemi has helped

me in preparing this folio.Do not forget to my parents

and siblings that give me many ideas. Without them, I might not be able to complete this

folio.

ContentsCONTENTS PAGE

Acknowledgement 1Group Members 2Biodata 3-7Introduction 8-10Problem 11Aim 11Variables 12Hypothesis 13Apparatus 13-14Procedure 15-17Observation 18-19Result 20-22Conclusion 22Graph 23Summary 24Reference 25Appendix 26-27

Name : Dhivashini a/p Siva rajah

Age : 12

Class : 6 Suria

School Name : SJK (T) Klebang

Hobby : Reading Story Books

Address : No.82 Hala Klebang Restu 1, Medan Klebang Restu,

31200 Chemor, Perak

Ambition : Doctor

Reference

Year 6 Science Text BookYear 6 Science BookNexus Reference BookSuccess Reference Book

www. science project.com.my/www.google.com.my/toycar

www.wikipedia.com.my /energy www.america’scarmuseum.com.my/

NAME : DHIVASHINI SIVA RAJAH

AGE : 12

CLASS : 6 SURIA

R.JEEVAANANTHAN

S.DHIVASHINI

V.GIVITAH G.RAVIENDRAN

V.PRIYA SRI