Note



Food Spoilage
1.     Our food comes from animals and plants.
2.    In normal conditions, fresh food such as meat, fish, fruits and vegetables cannot last long.
3.    Foods will turn bad if we keep them for a long time.
4.    Food turns bad because of bacteria and fungi.
5.    When food spoils it usually changes in appearance.
6.    Spoilt food has one or more of them following characteristics.
an unpleasant smell ( bad smell )
an unpleasant taste ( bad taste )
a changed colour
a changed texture
mouldy

Food
Characteristics of spoilt food
Rice



 



ó change colour –-  becomes dark
ó change texture – becomes slimy
ó mouldy – have dark spots

Milk



 
 




ó  unpleasant smell – bad smell
ó  unpleasant taste – sour taste
ó  changed texture – becomes curd
ó changed colour – becomes yellowish

Meat



 
 

ó unpleasant smell – bad smell 
ó changed colour – turns brown

Vegetables



 
 



ó changed colour – becomes yellowish
óchanged texture – becomes limps and wilted

Bread



 
 


ó changed colour – becomes dark
ó mouldy – have dark spots





The Conditions for Microorganisms to Grow
1.     Microorganisms need certain conditions to grow.
2.    The conditions for microorganisms to grow are :
a)    Air
b)   Water
c)    Nutrients
d)   A suitable temperature
e)   A suitable acidity
3.    Bacteria and fungi cannot grow if there is no air.
4.    Bacteria and fungi can easily grow in  damp and warm conditions.
5.    Bacteria and fungi cannot grow at a very high temperature because the strong heat can kill the bacteria and fungi.
6.    Bacteria and fungi cannot grow if there is no water.
7.    Bacteria and fungi cannot grow in a very acidic medium or a very alkaline medium.

bacterial
bacterial
fungi

fungi


         FOOD  PRESERVATION
1.     We can prevent food from going bad or at least delay it.
2.    We preserve food to make it last longer.
3.    Food preservation makes food last longer by delaying it from becoming bad.
4.    Food preservation is important because it makes food last longer and kills bacteria and fungi.
5.    We can make the environment unsuitable for microorganisms to live in.
6.    We preserve food by :
a)    Keeping it dry.
b)   Keeping it hot or frozen.
c)    Keeping it airtight.
7.    The following are ways to preserve food:
a)    Drying
b)   Boiling
c)    Cooling
d)   Vacuum- packing
e)   Pickling
f)    Freezing
g)   Bottling /canning
h)   Pasteurising
i)     Salting
j)    Smoking
k)   Waxing



 Drying
1.     Drying involves the removal or water from food substances.
2.    We can dry food by:
leaving it in the sun
heating it in the oven
heating  it with a flame
3.    Without water in food , bacteria and fungi cannot grow.
4.    Examples of food preserved by drying are fish, prawns, cuttlefish and fruits.
5.    We can make this process more effective by adding salt to the food before it is dried.

Drying of salmon
Dried tomatoes


Vacuum - Packing
Airtight-sealing in vacuum-sealed packaging has been adapted at an industrial scale. A vacuum is without oxygen, prohibiting bacterial growth and oxidation. Nuts are commonly vacuum-sealed to preserve flavor.

vacuum meat

Cooling
Home freezers offer one of the most natural and economical methods of food preservation and storage, and when used in conjunction with microwave oven, they are invaluable in a busy household. Follow the correct procedures and the food will loose none of the flavour, texture, and quality it had on the day you bought it.
Freezing halts the growing of bacteria, but only temporarily. It does not kill bacteria, so remember than when foods thaws it will be in the same condition as it was before freezing, and the food must then be treated in the same as any fresh produce.

cooling of meat

Boiling
We can preserve food by boiling them. When food is boiled, all bacteria and fungi will be killed.



boiling of carrots

Pickling
Pickling is a way of preserving food. The most common vegetables pickled today are cucumbers, olives and onions.

Pickling is a way of preserving food by storing it in acid, either directly by using vinegar or by fermenting food in salty water to make lactic acid. Herbs like garlic and mustard are often added to pickles both for flavour and to help keep germs at bay.



pickling of food and vegetables

salting
Salting is the preservation of food with dry edible salt.  It is related to pickling (preparing food with brine, i.e. salty water). It is one of the oldest methods of preserving food, and two historically significant salt-cured foods are dried and salted cod (usually referred to as salt fish) and salt-cured meat. Vegetables such as runner beans and cabbage are also often preserved in this manner.
Salting is used because most bacteria, fungi and other potentially pathogenic organisms cannot survive in a highly salty environment, due to the hypertonic nature of salt. Any living cell in such an environment will become dehydrated through osmosis and die or become temporarily inactivated.
It was discovered in the 19th century that salt mixed with nitrites (saltpeter) would color meats red, rather than grey, and consumers at that time then strongly preferred the red-colored meat.
salted tomatoes

salted fish

Smoking
Smoking is one of the oldest food preservation methods along with drying and burial, when food was cooked over open fires.
Smoked meats traditionally were sliced thin and placed over a fire where three modes of preservation took place: The heat of the fire killed harmful microorganisms, some of the chemical compounds in the wood being used for smoking had an anti-microbial actions, and dehydration prevented
Smoking is used to lengthen the shelf life of perishable food items. This effect is achieved by exposing the food to smoke from burning plant materials such as wood. Most commonly subjected to this method of food preservation   are meats and fish that have dergone curing.Fruits and vegetables like paprikacheesesspices, and ingredients for making drinks such as malt and tea leaves are also smoked, but mainly for cooking or flavoring them.
smoking of fish

Canning and bottling
Canning is probably the best known method of home food preservation using glass jars (or metal cans) with pressure-sealed lids, and includes processing by water bath or pressure canner. The water bath method of canning can be used with foods such as high-sugar jams and jellies or acidic tomato products and pickles. Water bath canning is accessible to most homeowners who have the desire to dip their toe in food preservation methods. Canning a fruit jam is a recommended first step for the soul who is interested in stepping into the world of home food preservation.


Pressure canning of foods is needed for non-acid foods including many vegetables like beans and potatoes, and meats. A pressure canner (as opposed to a pressure cooker) is required for canning these items, and it is recommended that someone have some water-bath canning experience under their belt before purchasing and using a pressure canner. But the versatility a pressure canner brings to the home storage kitchen is worth its weight in gold.

can sardines

bottle drinks

8 comments:

  1. Well done & thanks for sharing! Keep it up.^^

    ReplyDelete
  2. Terima kasih atas komen cikgu-cikgu.

    ReplyDelete
  3. satu blog yang sangat baik . Nota yang diberi sungguh lengkap dan gambar pun menarik . memang bermanfaatkan kepada semua pihak

    ReplyDelete

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