Tuesday, 27 November 2012

Exercise - Check Your Understanding

1. Fill in the blanks with the correct words.

    a. Food is heated before canning to kill ______________ .

    b. _______________ is the process of drying food with smoke.

    c. Freeze-dried food are easy to store and  ________________ .

2. Which of the following is not a reason why we need to preserve food ?

    a. For food to last longer                     b. For food to be stored easily

    c. To reduce wastage of food              d. To reduce the time taken for food to cook

3. Arrange the steps to salt fish in the correct order.

     P - Clean the fish with water

    Q - Rub salt into the fish

    R - Remove the internal organs of the fish

    a. P - Q - R         b. Q - P - R         c. P - R - Q        d. R - P - Q

4. Daniel investigated the time taken for moulds to grow on a piece of bread. He took two pieces of bread  
    and sprayed one of them with water. The results of his investigation are shown below.
Time taken for mould to grow ( days)
Without water
Sprayed with water

     a. In this investigation , identify what did Daniel:
         i. keep the same
         ii. change
        iii. observe

    b. What is the purpose of this investigation ?

    c. Name other factors that allow moulds to grow.

My Experiment photos

Tuesday, 20 November 2012

Year Six - The way to preserve food ( Part 4 )

8. Cooling and Freezing

   - are the most common forms of food preservation.
   - Cooling slows down the action of microorganisms, thus it take longer to
   - It allows fruit from different parts of the world to appear on our
     supermarket shelves.

   - At freezing temperature,microorganisms become inactive,thus food cannot
     spoil when it is frozen.


  - kills most bacteria. However, those not affected by heat will grow when the
    conditions are suitable.

10. Smoking

  - is the process of drying food with smoke for a long period of time.

  - This method is mainly used for fish,meat and fruit such as banana.

  - The drying effects of smoke and the chemicals produced from the smoke help
    to preserve the food.

Year Six - The way to preserve food ( Part 3 )

4. Drying

   - removes most water from food. Most bacteria die or become inactive when
     the food is dried.

5. Vacuum packing

   - keeps food by sucking air out from its packaging. Food is thus prevented
     from spoiling because there is no air.

6. Pasteurization

   - heating food to a certain temperature for some time followed by rapid
     cooling. Heating at such high enough temperature kills most bacteria.
     However,it does not affect the taste and nutritional value of the food.
7. Waxing

   - fruit and vegetables is also common.Apples,Oranges,Eggplants and Tomatoes
     are dipped into liquid wax to prevent growth of fungi and loss of moisture.

Year six - The way to preserve food ( Part 2 )

2. Pickling

   - Food in vinegar or other acids, makes it difficult microorganisms to live.
     Commonly pickled food include onions, parkias, soya beans and chillies.

   - Sugar can also be used in pickling fruits such as nutmegs, mangoes and

3. Salting

   - is an age-old way of preserving food. The salt draws out moisture and
     prevents microorganisms from growing.In this process, food such as fresh
     fish are gutted, washed and coarse salt is rubbed into it.

Year Six - The way to preserve food ( Part 1 )

1. Bottling and Canning

   - processes of preserving food by heating and then sealing it in an airtight
     container. The food is boiled to kill microogarnisms and then sealed to 
     prevent other microorganisms from getting in.

Year Six - Food Preservation

- Food undergoes changes that makes it spoil.These changes can be detected by
  smell, taste, touch or sight.Spoilt food is unsafe to eat.

- Stickiness under the chicken wings and darkening of their tips indicate  

- Fish is no longer fresh when the flesh has changed texture. It is no longer
  firm when pressed with a finger. It also has an unpleasant smell.

- We are blessed with many varieties of food. However, our food may be infected
  with microorganisms.Microorganisms such as fungi and bacteria can cause 
  food to spoil.

- The fruit and vegetables above have been affected by moulds. They become 
  mouldy and changed colour.

- Food turns sour because the bacteria in it produced acids. A common example
  is when the milk turns sour, giving it an unpleasent taste.When it is  
  opened, frothy liquid and an unpleasant smell will indicate spoilage.