Science Year 6 : Food Preservation

Food Spoilage

1. Food can spoil after a certain period of time.
2. Spoilt food will change in texture and taste.
3. One can get food poisoning by eating spoilt food.
    a) Food poisoning can lead to stomach upset, diarrhea and vomiting.
    b) Serious food poisoning may cause death.
4. Foods which are spoilt can be identified by observing, touching, smelling and tasting.
5. Spoilt food has one or more of the following characteristics.
    a) Unpleasant smell
    b) Unpleasant taste
    c) Changed colour
    d) Changed texture
    e) Mouldy

Food Preservation

1.    Food preservation is a process that makes food last longer.

2.    Food preservation can prevent or slow down the action of bacteria or fungi on

    the food.

3.    There are many methods to preserve food.

    *   Drying

    *   Boiling

    *   Cooling

    *   Vaccum packing

    *   Pickling

    *   Freezing

    *   Bottling & Canning

    *   Salting

    *   Smoking

    *   Pasteurising

    *   Waxing

Salting

1. Food can also be preserved with salt. This process is called salting.
2. Salting can be done in two ways as shown below.
    a) Adding a lot of salt to the food.
    b) Soaking the food in a salt solution.
3. Bacteria and fungi cannot grow in salty conditions. Hence, salted foods last longer.
4. Examples of food that can be preserved by salting are fish, meat,   
    eggs, vegetable and fruits.
5. Salting will change the taste, colour and destroy food nutrition.

Pasteurising

1. Pasteurising is a process in which milk is heated at 63 °C for 30 minutes or heated  
    at 72 °C fo 15 seconds and followed by rapid cooling to below 10 °C.
2. The pasteurised milk can then be refrigerated to last a few days.
3. Friut juice can also be preserved in this way.
4. This method of preservation retains the natural flavour of milk. Nutriens like vitamins
    are not destroyed.

Canning/ Bottling

1. Some foods can be canned and bottled. The canning and bottling of food allows the food to be kept for a very long time.
2. These methods of preservation involve:
    a) heating of the food to a very high temperature - can kill bacteria and fungi
    b) keeping foods in airtight cans or bottles - to prevent the entry of air that may    

        contain bacteria and fungi
3. Therefore, canned or bottled foods can be kept for a long time in months or years.
4. Examples of food that can be perserved by canning or bottling are shown below.

·         fish

·         meat

·         beans

·         corn

·         mushroom

·         chicken

·         pineapple

·         condensed milk

·         jam

·         soft drink

·         soy sauce

·         syrup

·         tomato sauce

·         fruit juice

Boiling

1.   Boiled foods may last longer than unboiled foods.
2. When food is boiled, all bacteria and fungi will be killed.

Drying

1. We can dry food to remove water from the food.

2. Without water in food, bacteria and fungi cannot grow. This can make the food last  

    longer.

3. Drying foods can be done as follows.

a) Drying the food under hot sun

b) Heating food to a high temperature

4. The disadvantage of this method is that the food becomes less nutritious because

    some nutrition may be lost during the process.