Food Preservation and Methods physical methods simple notes

Physical methods Food Preservation and Methods

Food preservation is essential for extending the shelf life of food products, maintaining their nutritional value, and ensuring food safety. Various methods and principles are applied in food preservation to prevent microbial degradation, self-decomposition, and damage from insects, animals, or mechanical causes. Here, we discuss several methods and the principles behind them.



Principles of Food Preservation

  1. Preventing or Delaying Microbial Degradation

    • Asepsis: Keeping microorganisms out of food through sterile conditions.
    • Filtration: Removing microorganisms using filters.
    • Growth Inhibition: Using low temperatures, drying, anaerobic conditions, or chemicals to stop microbial growth or activity.
    • Microbial Destruction: Killing microorganisms through heat or radiation.

  2. Preventing or Delaying Self-Decomposition

    • Enzyme Inactivation: Destroying or inactivating food enzymes, e.g., through blanching.
    • Use of Antioxidants: Preventing or delaying chemical reactions that cause food spoilage.

  3. Preventing Damage from Insects, Animals, or Mechanical Causes

High and Low Temperature Preservation

Heating Methods

  • Sterilization: Applying extreme heat (e.g., 112°C for 1 hour or 121°C for 3 minutes) to eliminate all pathogenic bacteria. This method is used for canned food, allowing it to be stored at room temperature for years.
  • Pasteurization: Using milder heat treatments (e.g., 90°C for 10 minutes or 72°C for 2 minutes) to extend shelf life by killing some, but not all, bacteria. Pasteurized products typically last 3-5 weeks when chilled.

Cooling Methods

  • Cold Storage: Keeping food at temperatures of 4°C or lower to slow down microbial growth.
  • Freezing: Storing food at -20°C or lower to halt microbial activity and convert water to ice, further preserving the food.
  • Supercooling: Maintaining temperatures around -1°C to extend the shelf life of products like fresh salmon when combined with a modified atmosphere.

High Pressure Preservation (HPP)

HPP is a non-thermal technique that uses intense pressure to kill microorganisms without significantly affecting the taste, texture, appearance, or nutritional value of food. It's effective against pathogens like Listeria monocytogenes, Salmonella, and E. coli and can be used on raw and processed foods.

Drying Food Preservation

Drying involves removing water from food to inhibit microbial growth and enzyme activity. Methods include:

  • Sun Drying: Using natural heat from the sun.
  • Artificial Drying: Using controlled heat sources to dehydrate food.

Stages of Drying

  • Constant Rate Period: Moisture evaporates from the food surface at a consistent rate.
  • Falling Rate Period: The drying rate slows as the moisture content drops below a critical level, making it harder to remove remaining water.

Modified Atmosphere Packaging (MAP)

MAP alters the composition of the air around the food product to slow spoilage and extend shelf life. This technique is used for meats, fruits, vegetables, and other consumables, including coffee beans and cannabis. By controlling the levels of oxygen, carbon dioxide, and nitrogen, MAP helps preserve the freshness and quality of food products.

Pulsed Electric Field (PEF) Preservation

PEF is a non-thermal method that uses short bursts of high-voltage electrical energy to inactivate microorganisms and enzymes without significant heating. This process helps retain the sensory and nutritional qualities of food better than traditional thermal methods.

Aseptic Packaging

Aseptic packaging involves sterilizing both the food product and the packaging materials, then filling and sealing the product in a sterile environment. This method maintains the sterility and quality of the food without the need for refrigeration or preservatives.

Manothermosonication

Manothermosonication combines heat, pressure, and ultrasound to inactivate enzymes more effectively than heat treatment alone. This method is especially useful for inactivating thermally labile enzymes and can be applied to a variety of food products.


In summary

To sum up, food preservation is essential to preserving food's availability, safety, and quality. There are several advantages to using these procedures, which range from antiquated practices like pickling and drying to modern innovations like aseptic packing and high-pressure processing. They improve safety, maintain nutritional content, increase shelf life, and offer convenience. We can drastically cut waste, save money, and improve food security by storing food well. This will guarantee that people everywhere have access to healthy food all year long.





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