2.5 Food Processing Technology
Most raw food substances cannot be eaten fresh and spoil quickly. Food processing technology converts raw food into forms that last longer, are more delicious and attractive, and can be digested easily.
Learning Objectives
- Describe the purpose and importance of food processing technology.
- Explain the methods of food processing along with examples of food products.
- State the types, functions, and examples of natural and artificial chemical substances used in food processing.
- Explain the adverse health impacts of excessive intake of chemical substances used in food processing.
Summary of Food Processing Methods and Chemical Additives
Compare physical processing techniques and map chemical additives to their functions and health effects.
Short Explanation
Definition
Food processing technology is used to convert raw food into forms that last longer, are more delicious and attractive, and can be digested easily.
Various processing methods are employed to inhibit or kill microorganisms, stop enzyme action, and prevent chemical spoilage. Additionally, approved food additives are used to enhance quality, although consuming them in excess can cause adverse health effects.
Physical methods target microbial growth and enzyme activity. Heat destroys vegetative cells and spores; moisture reduction dehydrates cells; cold temperatures halt enzyme activity; radiation disrupts microbial DNA; and air extraction eliminates oxygen needed by aerobic bacteria.
Excess chemical intake is dangerous. Excessive consumption of synthetic chemicals can cause severe long-term complications including organ damage, allergic reactions, and cancer.
Methods of Food Processing
Eight physical methods preserve food through heat, cold, moisture removal, radiation, or air extraction.
1. Cooking
Heating food using techniques such as blanching, frying, grilling, smoking, braising, stir-frying, baking, and steaming. Examples: chicken curry, fried fish, grilled chicken, rice, vegetables, and cakes.
2. Fermentation
Breakdown of complex substances into simpler substances through the action of bacteria, yeast, or other useful microorganisms. \[ \text{Glucose} \xrightarrow{\text{Yeast}} \text{Ethanol} + \text{Carbon dioxide} \] Examples: soy sauce, kimchi, tempeh, yoghurt, tapai, and bread.
3. Dehydration or Drying
Water is removed from food through dehydration or evaporation by drying under the sun, using flame or smoke, or in an oven. Examples: dried shrimp, dried squid, dried fish, dried fruits, cereal, mushroom, and milk powder.
4. Pasteurisation
Liquid is heated to a temperature below its boiling point to kill pathogens and then cooled quickly. Heated to \(63^\circ\text{C}\) for 30 minutes, or heated to \(72^\circ\text{C}\) for 15 seconds, and then cooled immediately. Examples: fresh milk, dairy products, and fruit juices.
5. Canning
Food is placed in sterilised cans and heated to a temperature exceeding \(115^\circ\text{C}\) under high pressure to kill microorganisms and their spores. Air inside the can is removed before the can is sealed. The sealed can is heated again to kill any remaining microorganisms before being cooled quickly. Examples: meat, soup, beans, fish, fruits, sauce, and canned milk.
6. Freezing
Food is kept at a temperature of \(0^\circ\text{C}\) or lower so that it can last longer. Meat is frozen at \(-18^\circ\text{C}\) to \(-24^\circ\text{C}\). At temperatures below \(-18^\circ\text{C}\), enzyme action stops and the growth and reproduction of microorganisms are inhibited. Examples: seafood, meat, chicken, and fish.
7. Irradiation
Food is exposed to ionising radiation such as gamma rays, ultraviolet rays, and X-rays to kill microorganisms and insects. It also slows down seed germination, budding of root vegetables, and ripening of fruits. Examples: vegetables, cereal, and fruits.
8. Vacuum Packaging
Air is removed completely from the container or plastic bag before being sealed tight. The absence of air prevents the growth of microorganisms and stops food oxidation. Examples: nuts, rice, durian, and vegetables.
Chemical Substances Used in Food Processing
Natural and artificial additives improve quality, but excess intake can harm health.
| Chemical substance | Functions | Natural substances | Artificial substances |
|---|---|---|---|
| Preservative | Prevents growth and reproduction of microorganisms; reduces food spoilage; makes food last longer. | Salt, sugar, vinegar | Sodium nitrite, sodium nitrate, benzoic acid, boric acid, sulphur dioxide |
| Colouring | Adds colour to food; makes food look more attractive. | Pandan leaf, turmeric, milk, caramel, coconut milk | Tartrazine, sunset yellow, carmoisine |
| Bleach | Bleaches unwanted natural colour from food. | Activated carbon | Benzoyl peroxide |
| Flavouring | Improves the taste of food; makes food more delicious and fragrant; enhances natural flavour. | Sugar, salt, vinegar, pandan leaf, vanilla | Monosodium glutamate / MSG |
| Stabiliser | Prevents deposition of granules in liquid food; improves texture and thickens food. | Starch, gelatine, agar, acacia gum | — |
| Sweetener | Sweetens food and drinks. | Sugar, palm sugar, honey | Aspartame, sorbitol |
| Antioxidant | Slows down the oxidation of fatty food; prevents fruits and vegetables from turning brown. | Ascorbic acid / vitamin C, tocopherol / vitamin E | Butylated hydroxyanisole / BHA |
| Emulsifier | Emulsifies substances which do not mix such as fat and water; improves homogeneity, stability, and texture. | Lecithin from egg yolk or soya beans, pectin, monoglyceride | Magnesium stearate |
Impacts of Excess Chemical Substances on Human Health
Excessive intake of synthetic chemicals can cause serious long-term complications.
| Chemical substance | Health impacts |
|---|---|
| Preservative | Cancer, disrupts the human digestive system, allergy, rash and itchy skin, foetal defects in mother's womb, damages liver and kidney. |
| Colouring | Cancer, infertility, food poisoning, damages liver and kidney. |
| Bleach | Cancer, food poisoning. |
| Flavouring | Cancer, high blood pressure, heart diseases, mental retardation in children, damages liver and kidney. |
| Sweetener | Cancer, diabetes mellitus, allergy, rash and itchy skin, obesity, damages liver and kidney. |
| Antioxidant | Retards body growth, damages liver and kidney, rash and itchy skin. |
Try to Answer First
Answer in your mind, then press “Check Answer”.
What are the temperature and time combinations used in the pasteurisation of fresh milk?
Why must food in cans be heated to a temperature exceeding \(115^\circ\text{C}\) under high pressure?
What is the specific role of activated carbon in processing palm oil?
Common Mistakes
- Confusing pasteurisation with sterilisation / canning. Pasteurisation only heats liquids below boiling point to kill pathogens without destroying all spores or altering milk flavour drastically.
- Stating that freezing kills microorganisms. Freezing at \(-18^\circ\text{C}\) or lower stops enzyme action and inhibits the growth and reproduction of microorganisms, but it does not kill all microorganisms.
- Confusing emulsifiers with stabilisers. Emulsifiers mix immiscible liquids like oil and water, whereas stabilisers prevent the settling of solid particles and thicken texture.
Concept Misunderstandings
Food irradiation makes food radioactive and unsafe to touch or consume.
Food exposed to ionising radiation does not become radioactive; the radiation kills pathogens and pests and passes through without leaving radioactive residue.
Vacuum packaging keeps food sterile forever.
Vacuum packaging only removes air to stop aerobic microbes and oxidation; anaerobic microorganisms can still survive if the food is contaminated before packaging or stored incorrectly.
Summary
- Food processing technology extends shelf life, enhances taste and appearance, and improves digestibility.
- Methods include cooking, fermentation, drying, pasteurisation, canning, freezing, irradiation, and vacuum packaging.
- Chemical additives include preservatives, colourings, bleaches, flavourings, stabilisers, sweeteners, antioxidants, and emulsifiers.
- Excessive intake of these chemicals can lead to serious health issues such as cancer, food poisoning, heart disease, diabetes mellitus, and liver or kidney damage.
Short Activity
A. Objective Quiz
1 Which of the following conditions correctly describes the canning process used to destroy microorganisms and their spores?
2 What is the function of an antioxidant such as ascorbic acid when added to cooking oil or food?
B. Fill in the Blanks
3 At temperatures below \(-18^\circ\text{C}\) during freezing, enzyme action stops and the growth and reproduction of microorganisms are .
4 In vacuum packaging, air is completely removed to prevent the growth of microorganisms and to stop food .
C. Drag and Drop: Match the Chemical Substance to Its Function
Drag each chemical substance to the function it performs. On a phone, tap an answer first, then tap a matching box. Tap the Answer Choices area to return a selected item.
C. Match the Chemical Substance to Its Function
Write the correct chemical substance next to each function.
| Function | Chemical Substance |
|---|---|
| 1. Prevents growth of microorganisms, reduces spoilage, and makes food last longer | |
| 2. Mixes immiscible substances such as fat and water to improve texture and stability | |
| 3. Removes unwanted natural colour from food products like palm oil and sugar | |
| 4. Prevents deposition of granules in liquid food and thickens food texture |
Answer choices: Preservative • Emulsifier • Bleach • Stabiliser
