Introduction To Food Preservation

Food Spoilage

 Food can spoil after a certain period of time. Spoilt food will change in texture and taste.Spoilt food is unsuitable and unsafe to be eaten. One can get food poisoning by eating spoilt food.

 Food poisoning can lead to stomach ache, diarrhea and vomiting.

 Serious food poisoning may cause death.

 Microorganisms present in surrounding such as bacteria, moulds and yeast can cause food to spoil.
 The conditions needed  for microorganisms to grow are:
(a) air
(b) water
(c) nutrient
(d) suitable temperature
(e) suitable acidity

 Foods which are spoilt can be detected by observing, touching, smelling and tasting.

 Spoilt food has one or more of the following characteristics.

a) Unpleasant smell

b) Unpleasant taste

c) Changed colour

d) Changed texture

e) Mouldy 

f) Stickiness

g) Frothy

Food preservation is the process of treating and handling food to stop or slow down food spoilage, loss of quality, edibility or nutritional value and thus allow for longer food storage.

Smoking

Methods to preserve food.

Smoking
Food smoking is an ancient method of preserving food using wood smoke. It is the process of drying food with smoke for a long period of time.The drying effects of smoke and the chemicals produced from the smoke help to preserve the food. Smoking  is usually used to preserve  meat, sausages, fish or cheese, but can also include eggs, vegetables and nuts.


Pickling


Pickling was widely used to preserve meats, fruits and vegetables in the past, but today is used almost exclusively to produce pickles. Pickling uses the preservative qualities of salt ,combined with the preservative qualities of acid, such as vinegar. Acid environments inhibit bacteria. Pickling is done by soaking food in vinegar, salt solution or sugar solution.Pickling reduces the water content in food.This prevents the growth of bacteria and fungi, so the food preserved by pickling will keep longer.However, its taste and nutrient content will be different.Microorganisms cannot survive under acidic conditions.Unripe papaya, mango, nutmeg, chillies ,cherries and some vegetables such as cucumber , cabbage are suitable for pickling.

Salting, especially of meat, is an ancient preservation technique. The salt draws out moisture and creates an environment unsuitable for microorganisms to grow. A lot of our local foods are preserved by salting process, such as fish, egg and cencaluk.
Salting

Drying                                                                                                                       Drying

Drying is one of the oldest food-preservation methods. The early method of drying was through direct exposure to the sunlight.Drying removes most water from food. By removing moisture from food, bacteria and yeast which needed water to grow are inhibited. Indigenous people would dry meats by exposing them to sun and wind, hanging their catches on lines.Examples of  food preserved by this method includes meat, fruit such as apples,bananas, mangoes and papaya.Chillies and local crackers, keropok are some forms of dried food.

       

Freezing and Cooling
Freezing and cooling are the most common and popular forms of  food preservation in used today.Freezing is kept frozen at a temperature -10°C. Meat, poultry and fish are examples of food that are normally preserved by freezing.Freezing turns water in the food into ice, thus making it difficult for microorganisms to grow.The colder the environment, the slower the growth of microorganisms.The microorganisms become completely inactive but they are not killed.The microorganisms become active again at room temperature. Food that can be preserved by freezing are chicken, meat, prawns and cuttlefish.
Freezing preserves the quality and nutrient content of the food.                              
Cooling also can slows down the growth and action of microorganisms .In cool conditions, bacteria become less active, they do not reproduce or give off poisonous gases.Fruits and vegetables are examples of food that can be kept longer in cool temperatures. Low temperatures do not kill the bacteria and fungi, but it slows down their growth. Cooling also does not affect the taste or texture of the food.

                                  Freezing and cooling through refrigerator.                                   

Pasteurization is named after scientist Louis Pasterur ( 1862 ) who used the application of  heat to destroy microorganisms in food. The process of heating  milk or milk product to a certain temperature for a specified time. The milk heated at 63 °C for 30 minutes or heated at 72 °C for 15 seconds,  and followed by rapid cooling to below 10 °C.  The pasteurised milk (taking from http://www.wikihow.com/Pasteurize milk) can then be refrigerated to last a few days.  Friut juice can also be preserved in this way.. This method of preservation retains the natural flavour of milk.The nutriens like vitamins are not destroyed, and it does not affect the taste of food.

Boiling/heating

Heat can kill various microorganisms that can cause food turn bad.Heat can be used to sterilize food. When food is boiled, cooked, fried or grilled, the bacteria present in the food are killed.The disadvantages of boiling is that it leads to loss of nutrients when boiling too long.

 Vacuum-packing     

Vacuum-packing stores food in a vacuum environment, usually in an air-tight bag or bottle. The vacuum environment strips bacteria of oxygen needed for survival, slowing spoiling. Vacuum-packing is commonly used for storing nuts to reduce loss of flavor from oxidation. In this method of preservation, food is sterilized 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.

Bottling and canning

Bottling and canning are processes of preserving food by heating and then sealing in an airthight container.
Canning involves cooking food, sealing it in sterile cans or jars, and boiling the containers to kill or weaken any remaining bacteria as a form of sterilization. It was invented by Nicolas Appert. Foods have varying degrees of natural protection against spoilage and may require that the final step occur in a pressure cooker. High-acid fruits like strawberries require no preservatives to can and only a short boiling cycle, whereas marginal fruits such as tomatoes require longer boiling and addition of other acidic elements. Low acid foods, such as vegetables and meats require pressure canning. Food preserved by canning or bottling is at immediate risk of spoilage once the can or bottle has been opened.Almost all types of food can be preserved by canning.

 Canning
  Bottling


Waxing of  fruits  and vegetables is also common.Apples,oranges,eggplants ,cucumber and tomatoes are dipped into liquid wax to prevent growth of fungi and loss of moisture.It also makes the fruits and vegetables look shiny.

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SKOR A 
Taking from http://www.scorea.com.my...hall// enotes// As61514 html

Importance Of Preservating Food

It can keep longer

 It can easy to store

            It is safe for consumption

  Wastage is reduced

          It is easy to carry around

ENRICHMENT  ACTIVITY(Taking from Science Text book,page 72)

Making OPAK-OPAK

You need : 400g of grated tapioca, 100g of tapioca starch flour, cooking pot with water, kitchen scale, salt, edible food colouring, stove,tablespoon,oil and frying pan.

          1.     Mix the grated tapioca with the tapioca starch flour.

          2.     Add a pinch of salt to the mixture. You may also add  food 

               colouring or cumin for flavouring.

         3.     Scoop one tablespoon of the paste onto the top of a pot lid.

         4.     Press the paste with your fingers to form a thin layer.

         5.   Overturn and place the lid over the pot of boiling water 

         6.    Remove the lid after two minutes.

         7.   Peel off the cooked paste and leave it to dry in the sun for two
             days.

         8.   Fry your tapioca crackers in hot oil and enjoy them.

Tour to Kuala Gula and Butterworth

 Process of drying prawn.
                  
                                                 Process of making belacan

                                                                             
                                               









                               

 Visit the oat factory in Butterworth


Activites Teaching and Learning

 Activities discussion during the Science lesson.

                                 Experiment of boiling water and measurement.

                                                                                                        Presentation  the topic of  food preservation.







                                                                                                 
                                                                                                                    Observation of microorganisms of bread.

Relaxing music

(taking fromhttp://www.youtube.com/watch?v=ZvElHGvuJEY )