Food Preservation Methods Quiz

Food Preservation Methods

• Food preservation prevents or delays changes in food, making it inedible or undesirable.
• Crucial due to:
  • Seasonal food production
  • Distance between food source and consumption
  • Spoilage-related economic losses
  • Microbial contamination leading to illness

Methods of Food Preservation

• General Principles:

  • Prevention/delay of microbial growth
  • Prevention/delay of self-decomposition
  • Prevention of mechanical damage

• Microbial Control:

  • Asepsis: Keeping microorganisms out (e.g., filtration)
  • Removal of microorganisms (e.g., filtration)
  • Inhibiting microbial growth (Low temp, drying, anaerobic environment)
  • Killing microorganisms (heat or radiation)

• Prevention of Self-Decomposition:

  • Deactivating food enzymes (e.g., heat treatments)
  • Preventing chemical reactions (e.g., adding antioxidants to prevent oxidation)

• Prevention of Damage:

  • Appropriate packaging, stacking, and storage
  • Preservatives must not change the food's original nature

Achieving Preservation Goals

• Minimizing initial microbial load
• Creating unfavorable environment for growth
• Preventing physical damage

Specific Methods

• Asepsis (includes filtration): Prevents introduction of microorganisms, natural barriers, quality of raw materials, harvest/storage/transport conditions, processing plant conditions, aseptic approach, cleaning/sanitization, workforce training/awareness/buy-in, industrial packaging

• Filtration/Removal of Microorganisms: Limited to clear liquids (juices, beer, soft drinks, water, wine). Effective when combined with other methods. Washing raw foods, sanitation, trimming spoiled parts also important.

• Anaerobic or Gas Storage: Evacuating air and replacing with CO₂ or inert gas (nitrogen) within containers. Spores of some microorganisms may be resistant to heat but not anaerobic conditions.

• Vacuum Packaging: Removes all air. Modified Atmosphere Packaging (MAP): Gas atmosphere changes due to microbial activity and diffusion across packaging membrane (CO2, gas exchange). Controlled Atmosphere Packaging (CAP): Constant product environment throughout storage.

• Sous-Vide Processing: Packaging under vacuum in a barrier bag or container. Cooked in a high-moisture environment at a temperature sufficient for cooking/pasteurizing, not sterilizing. Important: some spores may survive this, e.g., Clostridium botulinum type E; heat-stable toxins (e.g., Staphylococcus aureus) are potential concerns. Improves nutritional quality and palatability.

• Use of Low Temperatures:

  • Reducing microbial metabolic activity
  • Stopping activity below freezing temperatures
  • Enzyme activity depends on temperature; a rise in temperature correlates with faster enzyme reaction rates. Temperature coefficient (Q10): for every 10°C increase, a 1.5-2.5 fold increase in enzymatic reaction rate, between 0 - 40 degrees celsius Q10 is 2.
  • Psychrotrophic (cold-loving) bacteria aren't affected as greatly by cold
  • Storage types include common/cellar (10-15°C), chilling/refrigeration (just above freezing), freezing (-18°C or below).
  • Microbial effectiveness of freezing depends on the microorganism, its physiological state, storage temperature, and duration, whether freezing is fast or slow, plus food composition factors (water content, high sugar/salt, acidity/low pH). Food should be sorted, washed, blanched or packaged before freezing to minimize microbial load.