principles-of-home-pres-ppt-1416c

what are the principles of food preservation

To prevent food spoilage as a result of growth of micro-organisms and breakdown of food by enzymes

What is autolysis

Self destruction, caused by enzymes present in the food;

What is microbial spoilage

Caused by the growth of bacteria, yeasts and moulds

What micro-organism need certain conditions to survive and reproduce

Temperature, oxygen, food, time, moisture, PH

How can temperature affect the growth of micro-organisms

freezing the food to retard growth of micro-organism activity

heating the food to destroy micro-organisms and prevent enzyme activity.

how can oxygen affect the growth of micro-organisms

Food kept in an airtight container will deprive micro-organisms of oxygen and prevent contamination

How can moisture affect the growth of micro-organisms

Reducing the moisture content of the food to make water unavailable to micro-organisms.

Placing food in a sugary solution will make water unavailable for the growth of micro-organisms

How can Ph affect the growth of micro-organisms

Placing food in an acidic or alkaline solution will inhibit the growth of micro-organisms.

Chilling foods

Reduces the temperature to between 1ºC -4ºC.

reduces spoilage caused by micro-organisms and enzymes.

Moulds can still grow in cold temperatures

freezing foods

Reducing the temperature of the food to below – 18ºC. Reduces the activity of the micro-organisms and enzymes.

Freezing also reduces the availability of water because ice crystals are formed

Disadvantages of freezing

Large ice crystals are formed when food is slowly frozen, this can damage the cell structure of the food .

micro-organisms do not die, they simply become dormant, retarding their growth.

blast freezing