Food Spoilage What is food spoilage?

Food spoilage means the original nutritional value, texture, flavour of the food are damaged, the food

become unsuitable to eat (unfit for consumption) and sometimes even harmful if eaten.

How does it occur?

1. By natural decay (decompose)

Moisture loss: this is easily demonstrated in fruit and

vegetables. These continue to respire after harvest.

Therefore the moisture which used to be replaced by soil

is now lost and not replaced. Therefore the food shrinks

and becomes limp and the skin wrinkly.

Action of enzymes : many enzymes are present in food and some are inactive until the food is

harvested or slaughtered. Once activated, they speed up the process of decay.

2. Microscopic form

- Bacteria

Bacteria are round, rod or spiral shaped microorganisms.

Bacteria may grow under a wide variety of conditions. There

are many types of bacteria that cause spoilage.

Bacteria generally prefer low acid foods like vegetables and

meat. Most bacteria are destroyed at around 60 degrees Celsius and multiply most

at 37 Degrees Celsius. Here, bacteria multiply by Binary Fission (a process of

dividing into two). At cold temperatures the bacteria are dormant.

- Yeasts

Yeasts are microscopic single- celled fungi. Found in air, soil and on the surface

of fruit.

- MouldsMs. J. Borg 1

Moulds are tiny plants including spores which, when dry, float through the air to

find suitable conditions where they can start the growth cycle again. They grow

on many types of food especially cheese, bread and fruit. They grow best in

warm and moist conditions. Mould can cause illness, especially if the person is

allergic to moulds. To prevent mould from growing store in cool and dry places

and heat the food.

Both yeasts and moulds can thrive in high acid foods like fruit, tomatoes, jams, jellies and pickles. Both

are easily destroyed by heat.

3. Chemicals

Chemical spoilage is where enzyme reactions can continue occurring after they have been harvested and

slaughtered. The fruits and vegetables can spoil as the exposure to air can cause it decompose due to

stress, the ripening also continues due to exposure and enzymes carry on with actions which causes

change.

Did you know?

The microorganisms that cause ordinary food spoilage aren't necessarily

harmful to us. In fact, centuries before refrigerators, the earliest sauces

and seasonings were used to mask the "off" tastes and smells of food that

had begun to spoil.

Perishable Foods What are perishable foods?

Perishable foods are ANY food that will spoil, rot, go bad very fast, such as within hours. Most perishable

(dies quickly) foods will not even last a few hours without refrigeration or freezing.

Example: Milk, cottage cheese, sour cream, ice cream, meat, pork, chicken.

Pretty much a perishable food is anything you would normally keep in the fridge or freezer

for several days, otherwise, if you left it out, it would go bad.

High risk foods

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These are foods in which harmful bacteria can grow. High risk foods are usually eaten without further

cooking, and are good sources of protein. Including:

- Cooked meat such as ham

- Cooked chicken

- Milk, cream, custard and milky desserts

- Cooked eggs

- Shellfish

- Cooked rice

- Soups and stews

Conditions for growth

There are several factors that effect growth.

Time the bacteria mould and yeast needs time to multiply or disperse.

Temperature: Warm conditions are needed for growth. If too cold, they

will lie dormant (inactive) and if too hot these are destroyed.

Food: Growth is enhanced by food. Most live and multiply on food. These

foods are called high risk food (refer to previous page). Low risk food are

those with high salt, sugar and acid content. That is why food preservation

methods are successful in preventing food spoilages, since they include a

lot of salt, sugar and/or acid.

Acid: Most cannot grow in a very acidic environments.

Moisture: Like any other living organism, water is needed for growth.

Many foods contain enough water for growth with the exception of dried food.

Oxygen: some bacteria need oxygen to grow (aerobic bacteria) while others do not (anaerobic bacteria).

Cross- Contamination

What is cross contamination?

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Cross contamination is the transfer of bacteria between raw and

cooked food.

Examples of cross contamination:

- Bacteria of raw meat can pass onto cooked rice.

- A chopping board used for raw meat could be used to slice

cooked ham.

- A bowl of mixing raw eggs could be used unwashed to mix a sandwich filling.

Controlling cross- contamination in the preparation of meals?

- Equipment that is used for food should not be chipped, racked or worn

since cracks in mixing bowls can provide hiding places for bacterial growth.

- Wooden chopping should not be _______ as they are absorbent to moisture

and cannot be easily cleaned or disinfected.

Food Poisoning

Food poisoning is an illness caused by ingesting (Eating) contaminated

food or water. The more the bacteria in the food the quicker the food

poisoning symptoms will occur. The symptoms vary depending on the

type of food poisoning but often include abdominal pain, diarrhoea,

vomiting, nausea and fever.

Main reasons for food poisoning:

- Food prepared too fare in advance and stored at room

temperature.

- Cooling food too slowly prior to refrigeration.

- Not reheating food to high enough temperatures to destroy food- poisoning bacteria.

- Undercooking

- Not thawing frozen poultry for sufficient time.

- Cross- contamination from raw food to cooked food.

- Storing hot food below 63 degrees Celsius.

- Infected food handlers

- Use of left- overs.

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