Food Preservation

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Food Preservation

• Chapter 27

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Food Spoilage

• Biological Changes
• Fermentation The conversion of carbohydrates to
  carbon dioxide and alcohol by yeast or bacteria.

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Food Spoilage

• Chemical Changes
• Enzymes play a significant role in catalyzing
  these reactions
• Proteases, also called proteolytic enzymes,
  split proteins into smaller compounds.

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Food Spoilage

• Physical Changes
• The most common physical changes occurring in
  foods as they spoil are evaporation, drip loss,
  and separation.
• Dehydrate To remove at least 95 of the water
  from foods by the use of high temperatures.
• Freeze-dry To remove water from food when it is
  in a frozen state, usually under a vacuum.

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Food Preservation Methods

• Drying is the food preservation process that
  consists of removing the foods water, which
  effectively inhibits the growth of
  microorganisms. Like
• Sun Drying

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Food Preservation Methods

• Commercial Drying
• The most important types of commercial drying
  are
• Conventional heat.
• Vacuum pulls the water out.
• Osmotic water drawn out by osmosis.
• Freeze-drying ice crystals vaporize.

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Food Preservation Methods

• Sublimation The process in which a solid
  changes directly to a vapor without passing
  through the liquid phase.

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Food Preservation Methods

• Cure To preserve food through the use of salt
  and drying. Sugar, spices, or nitrates may also
  be added.
• Fermentation
• Pickling uses vinegar to preserve foods.
• Edible coating Thin layer of edible material
  such as natural wax, oil, petroleum-based wax,
  etc. that serves as a barrier to gas and moisture.

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Food Preservation Methods

• Carbohydrates are required for the fermentation
  process.
• Throughout Asia, vegetables are still commonly
  fermented.
• In North America, foods most often preserved by
  fermentation are cucumbers, olives, and cabbage.

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Food Preservation Methods

• The purpose of edible coatings is fourfold
• 1. To increase shelf life by acting as a barrier
  to moisture, oxygen, carbon dioxide, volatile
  aromas, and other compounds whose loss would lead
  to deterioration.
• 2. To impart improved handling characteristics,
  such as the ability to bend more easily without
  breaking.
• 3. To improve appearance through increased gloss
  and color.
• 4. To serve as a vehicle for added ingredients
  such as flavors, antioxidants, antimicrobials,
  etc.

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Food Preservation Methods

• Canning is a two-step process
• First the food is prepared by being packed into
  containers, which are then sealed.
• Then the containers are canned, or heated to
  ensure that all microorganisms are destroyed.
• Sterilization The elimination of all
  microorganisms through extended boiling/heating
  to temperatures much higher than boiling or
  through the use of certain chemicals.

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Cold Preservation

• Refrigeration slows down the biological,
  chemical, and physical reactions that shorten the
  shelf life of food.
• All perishable foods should be refrigerated as
  soon as possible, preferably during transport, to
  prevent bacteria from multiplying.

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Cold Preservation

• Freezing makes water unavailable to
  microorganisms.
• The chemical and physical reactions leading to
  deterioration are slowed by freezing.
• Freezer burn White or grayish patches on frozen
  food caused by water evaporating into the
  packages air spaces.

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Heat Preservation

• Pasteurization A food preservation process that
  heats liquids to 160for 15 seconds, or 143F
  for 30 minutes, in order to kill bacteria,
  yeasts, and molds.
• Ohmic heating A food reservation process in
  which an electrical current is passed through
  food, generating enough heat to destroy
  microorganisms.

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Other Preservation Methods

• Irradiation A food preservation process in
  which foods are treated with low doses of gamma
  rays, x-rays, or electrons.

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Symbol for Irradiated Foods

• (Green) Radura

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Other Preservation Methods

• How is irradation is used
• Sterilization of medical equipment (instruments,
  surgical gloves, alcohol wipes, sutures, etc.)
• Sterilization of consumer products (adhesive
  bandages, contact lens cleaning solutions,
  cosmetics, etc.)
• Foods for immune-compromised hospital patients
  (e.g., AIDS, cancer, or transplant patients)
• Some foods for astronauts, who cannot risk
  foodborne illness
• Spices and seasonings used in products such as
  sausage and certain baked goods

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Other Preservation Methods

• Pulsed Light exposes the food to intense, very
  brief flashes of light, which disrupt the cell
  membranes of bacterial cells, but not that of the
  surrounding food.

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Other Preservation Methods

• High-pressure processing of foods inactivates
  foodborne microorganisms at low temperatures
  without the use of chemical preservatives.
• Pascalization A food preservation process
  utilizing ultrahigh pressures to inhibit the
  chemical processes of food deterioration.

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Other Preservation Methods

• Ozonation
• Ozone (an oxidizing agent) is commercially
  produced by exposing oxygen to an electrical
  current.
• Ozone is an effective disinfectant and sanitizer
  for many food products.

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Other Preservation Methods

• Aseptic and modified-atmosphere packaging (MAP)
• Hermetically sealed Foods that have been
  packaged airtight by a commercial sealing process.