HOME PRESERVATION

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what are the benefits of rapid freezing

produces small ice crystals, cause less damage to the structure of the food

what does dehydration do

reduces the water activity level, weight and the bulk of other food when moisture is removed it atop the microbes growth

how do you increase the rate of dehydration

vegetables are diced before drying, to increase their surface area

what is the principle behind dehydration

to remove moisture to prevent and microbial activity

sun drying

one of the most traditional methods of drying. slow and only practical in hot, dry climate.

food, such as fish, is also vulnerable to contamination through pollution and vermin

what is spray drying

fine spray of liquid is injected into a blast of hot air in a chamber.

Water evaporates within seconds, leaving the solid part of the product behind in powdered form.

what is fluidised bed drying

Warm air is blown upwards directly underneath the food, causing it to flow and remain separated.

what is tunnel drying

Hot air is blown over the product.

The system dries the food rapidly with little shrinkage, and leaves a high moisture content

what is a disadvantage of tunnel drying

the product tends to shrink and is less easy to rehydrate

what is roller drying

in paste form, is spread over heated rollers or drums which rotate slowly

The heat causes the moisture to evaporate leaving a dried product behind

accelerated freeze drying

the produce is frozen. Then the temperature is increased under a strong vacuum. This makes the frozen water sublime,

what are the benefits of accelerated freeze drying

little heating, so there is little shrinkage or flavour change and the product rehydrates well.

what does sugar preservation do

high concentration of sugar added during the jam making process makes the water unavailable, reducing the microbial activity through dehydration effect.

whay does salt preservation do

reduces the moisture content of the food, reducing the availability of water.

however it might change the taste of the food

what is pickling

covered in vinegar and other ingredients, often including spices.

high concentration of acid inhibits bacterial growth and multiplication

initial boiling of ingredients will destroy enzymes and micro-organisms

what is the aim of canning

To destroy all micro-organisms and their spores through the application of heat

how is canning achieved

by sterilising the food within air-tight containers to prevent re-contamination