B. Thermal (Heat) Processing
Purpose:
- Improves nutrient absorption and ensures microbiological safety.
Effects:
- Protein: Denatures proteins, making them easier to digest.
- Collagen: Converts collagen in animal products into gelatin (glutin), a water-soluble protein that aids digestion.
- Carbohydrates: Starch absorbs water, swells, and partially breaks down into simple sugars.
- Safety: Meat, poultry, fish, and eggs must reach ≥70°C to destroy harmful microbes.
Recommended Methods:
- Boiling: Use hot, lightly salted water; cover to reduce oxidation.
- Steaming: Preserves most nutrients.
- Microwave: Short cooking time minimizes protein denaturation and can reduce vitamin loss by up to 50%.
Less Recommended Methods (Hygienic Risks):
- Frying: High heat forms toxic compounds (peroxides, aldehydes) and increases fat content.
- Roasting/Grilling: Can produce mutagenic compounds, reduce protein digestibility, and lower nutrient availability.
Post-Cooking Safety:
- Consume cooked food promptly to prevent bacterial growth.
- Refrigeration: Store at ≤6°C if not eaten immediately.
II. Preservation of Food Products
Purpose: Extend shelf life by destroying or inhibiting microorganisms and enzymes.
A. Physical Methods:
- Cooling: ~0°C, inhibits non-spore-forming microbes, slows autolysis.
- Freezing: Stops microflora, minimizes oxidation, preserves nutrients.
- Pasteurization (<100°C): Destroys vegetative pathogenic microorganisms.
- Sterilization (>100°C): Destroys all microflora, including spores.
B. Chemical Methods:
- Salting/Sugar: High concentrations inhibit microbial growth; may destroy some vitamins.
- Marinade: Acidic pH (<4) prevents pathogen growth.
- Preservatives (benzoates, sulfites, nitrites, nitrates): Extend shelf life.
- Harmful effects: Some preservatives may cause allergic reactions, digestive irritation, or potential toxicity with excessive consumption.