2.5 Food Processing Technology

Purposes of Food Processing

• Converts raw food into forms that can be eaten or used.
• Makes food last longer.
• Makes food more delicious and attractive.
• Makes food easier to digest.

Food Processing Methods

Cooking

• Heats food by blanching, frying, grilling, smoking, braising, stir-frying, baking or steaming.
• Examples: chicken curry, fried fish, grilled chicken, rice, vegetables and cakes.

Fermentation

• Breaks down complex substances into simpler substances through bacteria, yeast or other useful microorganisms.

$\text{Glucose}\stackrel{\text{yeast}}{\to }\text{ethanol}+\text{carbon dioxide}$

• Examples: soy sauce, kimchi, tempeh, yoghurt and tapai.

Dehydration or Drying

• Removes water by dehydration or evaporation under sunlight, with flame or smoke, or in an oven.
• Examples: dried shrimp, squid and fish; dried fruits; cereal; mushroom; milk powder.

Pasteurisation

• Heats a liquid below its boiling point to kill pathogens, then cools it quickly.
• Fresh milk is heated at 63°C for 30 minutes or 72°C for 15 seconds, then cooled immediately.
• Examples: milk, dairy products and fruit juices.

Canning

1. Place food in sterilised cans and heat above 115°C under high pressure to kill microorganisms and spores.
2. Remove air and seal the cans.
3. Heat again to kill remaining microorganisms, then cool quickly.

• Examples: meat, soup, beans, fish, fruits, sauce and canned milk.

Freezing

• Keeps food at 0°C or lower; meat is frozen at −18°C to −24°C.
• Below −18°C, enzyme action stops and microorganism growth and reproduction are inhibited.
• Examples: seafood, meat, chicken and fish.

Irradiation

• Exposes food to ionising radiation such as gamma rays, ultraviolet rays and X-rays.
• Kills microorganisms such as Salmonella sp. and Campylobacter sp. in raw meat and pests such as weevils in rice.
• Slows seed germination, root-vegetable budding and fruit ripening.
• Examples: vegetables, cereal and fruits.

Vacuum Packaging

• Completely removes air from a container or plastic bag before sealing it tightly.
• Absence of air prevents microorganism growth and stops food oxidation.
• Examples: nuts, rice, durian and vegetables.

Chemical Substances in Food Processing

• Preservative: prevents microorganism growth and reproduction, reduces spoilage and extends shelf life.
  • Salt: seafood, vegetables.
  • Sugar: fruits.
  • Vinegar: pickled food.
  • Sodium nitrite and sodium nitrate: meat, sausage.
  • Benzoic acid: fruit juice, ketchup.
  • Boric acid: noodles, fish balls.
  • Sulphur dioxide: fruit cordial.
• Colouring: adds colour and makes food attractive.
  • Pandan leaf, turmeric, milk, caramel and coconut milk: cakes, drinks, candy, turmeric rice and ice cream.
  • Tartrazine: soft drinks, candy; sunset yellow: orange cordial; carmoisine: red cordial.
• Bleach: removes unwanted natural colour.
  • Activated carbon: palm oil, cane sugar.
  • Benzoyl peroxide: sugar, white rice, flour and rice noodles.
• Flavouring: improves taste and fragrance and enhances natural flavour.
  • Sugar, salt, vinegar, pandan leaf and vanilla: cakes, ice cream.
  • Monosodium glutamate (MSG): instant noodles, soy sauce and potato chips.
• Stabiliser: prevents granule deposition, improves texture and thickens food.
  • Starch: chilli sauce, ketchup; gelatine: jelly; agar: ice cream, instant soup and jelly; acacia gum: ice cream, candy and jelly.
• Sweetener: sweetens food and drinks.
  • Sugar, palm sugar and honey: cakes, drinks.
  • Aspartame: cordial, drinks and jam; sorbitol: food for diabetic patients.
• Antioxidant: slows oxidation of fatty food and prevents fruits and vegetables from browning.
  • Ascorbic acid or vitamin C: cooking oil; tocopherol or vitamin E: margarine and biscuits; butylated hydroxyanisole: vitamin pills.
• Emulsifier: mixes substances such as fat and water; improves homogeneity, stability and texture.
  • Lecithin from egg yolk or soya beans: ice cream, chocolate.
  • Pectin: mayonnaise, pudding.
  • Monoglyceride and magnesium stearate: yoghurt, cheese.

Effects of Excess Chemical Substances on Health

Substance	Possible effects of excessive use
Preservative	Cancer; digestive-system disruption; allergy, rash and itchy skin; foetal defects; liver and kidney damage
Colouring	Cancer; infertility; food poisoning; liver and kidney damage
Bleach	Cancer; food poisoning
Flavouring	Cancer; high blood pressure; heart disease; mental retardation in children; liver and kidney damage
Sweetener	Cancer; diabetes mellitus; allergy, rash and itchy skin; obesity; liver and kidney damage
Antioxidant	Retarded body growth; liver and kidney damage; rash and itchy skin