Chapter 7 part 2 food biotech

• Food Preservation is the process of treating and handling food to stop or greatly slow down spoilage caused by micro-organisms
• Preservatives are substances that maintain or preserve a food product's freshness
• Causes of food spoilage include biological changes, chemical changes, and physical changes
• Biological changes are caused by yeast, mold, and bacterial action
• Chemical changes are catalyzed by enzymes, leading to food deterioration
• Physical changes in food as they spoil include evaporation and drip loss
• Methods of food preservation:

  • Removal of Moisture
  • Heat Treatment
  • Cold Preservation
  • Acidity Control
  • Traditional Non-Thermal Processing
  • Innovative Non-Thermal Processing
• Removal of Moisture aims to stop/reduce microorganisms growth, enzymatic, and chemical reactions by removing water and moisture. However, will depend on water activity.
• Commercial Drying methods include Conventional (heat), Vacuum (pulls the water out), Osmotic (water drawn out by osmosis), and Freeze-drying(ice crystals vaporize).
• Heat Treatment uses high temperatures to destroy enzymes and microorganisms that could reduce food quality and safety
• Heat Treatment methods include Blanching, Pasteurization, Sterilization, and Canning
• Cold Preservation uses low temperatures to store food and prevent spoilage by microorganisms and chemical reactions. Cold preservation includes refrigeration ( 0 to 10 degrees Celcius) and Freezing (-18 to -20 degrees Celcius).
• Acidity Control involves controlling pH levels. Acid stress microbial growth, denature protein molecules, weaken cell membranes of microbe will prevent microbial growth
• Traditional Non-Thermal Processing methods include Cured food preservation, Pickling, and Packaging
• Objectives of Heat Treatment methods:

  • Blanching: Only on vegetables and fruits. Inactivates natural enzymes and reduces microbial load
  • Pasteurization: destroys pathogenic bacteria, reduce microbial load, inactivate enzymes, and extends shelf life
  • Sterilization: to complete destruction of microorganisms
• Blanching is done at around 70°C for a short time and is followed by cooling to avoid excessive tissue softening. After cooling, then followed by freezing/canning.

• Pasteurization is done at 80-90 °C for 30 minutes and must be stored under refrigeration to inhibit surviving microorganisms.
• Sterilization involves treating each particle in food at 121°C with wet heat for 15 minutes
• Traditional Non-Thermal Processing methods:

  • Cured food preservation: uses salt, sugar, spices, or nitrates
  • Pickling: uses vinegar to preserve foods
  • Packaging: protects from biological, chemical, and physical hazards
• Packaging objectives include protection from hazards and may use materials like plastic, glass, or cans

  
  

  Modified Atmosphere Packaging: prevent oxidation, material packaging like PVC, PVDC, PP varying permeability of gas, moisture

  Vacuum packaging: removes air from the package, flushing with N2 and CO2, delays senescence in fruits

  Smart packaging: antimicrobial agents embedded in packaging, oxygen-sensitive baked products, and precut salads in bags that permit gas exchange.
• Aseptic packaging involves sterilizing the food product and the container it will be placed in
• Innovative Non-Thermal Processing methods:

  • Food irradiation: exposes food to gamma rays to destroy microorganisms
  • Pulsed electric fields: inactivate microorganisms in food products
• Food irradiation uses gamma rays to destroy enzymes or microorganisms in food products
• The removal of moisture includes drying (sun drying, 'drum drying, spray drying, freeze drying, puff drying), dehydration, evaporative concentration, and intermediate moisture processing.
• Freeze-drying is the process where foods are processed by low-pressure chilling under a vacuum, allowing moisture to form ice crystals slowly, which are then evaporated into the gas phase without going through the liquid phase.
• Advantages of drying:

  • produces concentrated form of food
  • inhibits microbial growth and autolytic enzymes
  • retain most nutrients

  Disadvantages of drying:

  • can cause loss of some nutrients (thiamin, vitamin C)
  • sulphur dioxide is sometimes added to dried fruits to retain vitamin C, but some individuals are sensitive to this substance
• Factor influencing the choice of heat treatment:

  • types of food
  • level of contamination
  • presence of oxygen
  • heat resistance of organisms or enzymes
  • heat penetration ( characteristics of the food)
  • packaging material
  • size of container
  • sensory qualities desired
• Commercially sterile product (canning) - sterilization at which all pathogenic and toxin-producing organisms, are destroyed as well as any spoilage microorganisms. Use a high heat and absence of oxygen.
• Canning methods:

  • still retorts
  • agitation
  • aseptic
  • ohmic
  • pressure
  • sous-vide (under vacuum)
  • microwave
• Aseptic canning

  canning is a two-step process:

  1. food is prepared by being packed into containers, which are then sealed
  2. then the containers are "canned", or heated to ensure that all microorganisms are destroyed.
• Acidulants: food additives to lower pH (benzoic acid, citric acid, acetic acid)
• Canned foods with low acid:

  • not acidic enough to prevent the growth
  • need to be heated to high temperature

  Canned food with high acid:

  • foods need not to be heated to high temperatures to achieve commercial sterilization.
• Hermetically sealed: Foods that have been packaged airtight by a commercial sealing process
• Innovative Non-Thermal processing is the technology to effectively activate microorganisms and enzymes in food products but retaining nutrients and freshness.
• The aims of Irradiation:

  • reduce microbial levels
  • destroy pathogens
  • extend shelf life
  • remove insect infestation
• Irradiation: A food preservation process in which foods are treated with low doses of gamma rays, x-rays, or electrons.