35. Food processing and preservation

Name 4 major food processing techniques.

• Canning

• Freezing

• Drying

• Extrusion

name 4 "latter" (traditional) preservation technologies.

• Pasteurisation

• Autoclavation

• Drying

• Salting

Name 3 modern separation techniques used in food concentration.

• Milling

• Centrifugation

• Pressing

How do processed foods differ from whole/fresh foods?

• Reduced nutritional value

• May contain harmful substances like oxidized fats and trans fats

Give 2 diseases caused by food processing errors.

1. Beri beri from polished rice → thiamine deficiency

2. Scurvy from pasteurized milk → vitamin C deficiency

What principle does canning rely on for preservation?

Time and temperature (each temp increase kills more microbes)

Which vitamins are destroyed during canning?

• Thiamine (heat)

• Vitamin C (ascorbic acid oxidase unless destroyed)

Which vitamins are stable during canning?

• Riboflavin (stable to heat, sensitive to light)

• Fat-soluble vitamins (unaffected)

Are minerals affected by canning?

No, minerals remain unaffected

How does canning preserve vitamin C?

By destroying ascorbic acid oxidase.

What is the “HTST” principle in canning?

High-Temperature-Short-Time processing to preserve nutrients while killing microbes.

Does freezing destroy nutrients?

No, but some nutrients may be lost during processing steps.

How can nutrient retention in frozen food be maximized?

Store at lower temperatures and keep foods frozen properly.

What are the advantages of food drying?

• Eliminates microbial spoilage

• Reduces weight and volume

• Minimal nutrient loss

Which drying methods conserve nutrients best?

Vacuum puff drying and freeze drying

Why are sulfites added when drying fruits?

To prevent browning and preserve vitamin C

• but they destroy thiamine.

What is extrusion?

A process where food is heated, ground, and pushed through screens to form shapes (e.g., cereal).

What are the downsides of extrusion?

• Considerable nutrient loss

• Even after fortification, they still lack vitamin E