FOOD PRESERVATION BY SALT, ACID, SUGAR AND CHEMICAL PRESERVATION

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FOOD PRESERVATION BY SALT, ACID, SUGAR AND
CHEMICAL PRESERVATION
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SALT AND ACID

• Salt was used by man as one of the earliest
  methods of food preservation.
• Smoking and drying is used extensively in
  combination with salt, particularly for meat and
  fish product.
• Salt and acid are use extensively in the
  preservation of vegetable product of which
  cucumbers, cabbage, and onions are important
  examples.

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ANTI-MICROBIAL PROPERTIES OF SALT AND ACID

• Salt produces a number of effects when added to
  fresh plant tissues
• Salt exerts a selective inhibitory action on
  certain contaminating microorganisms.
• Salt also affects the water activity (aw) of the
  substrate, thus controlling microbial growth by a
  method independent of its toxic effects.

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• Acids, chiefly acetic and lactic, can be present
  in preserved foods as a result of acid addition
  to non-fermented foods, or as a result of
  microbial fermentation of tissue carbohydrates.
• Acids have two anti-microbial effects one is
  due to their effect in pH, and the other is the
  specific toxicity of the undissociated acid which
  carries for different acids.

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SUGAR

• Sugar are involved in the preservation and
  manufacture of wide range of food products.
• Some of the more common include jams, jellies,
  fruit juice concentrates, sweetened condensed
  milk.
• When sugars are added to foods in high
  concentration (at least 40 soluble solids), some
  of the water present becomes unavailable for
  microbial growth and the aw of the food is
  reduced.

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CHEMICAL PRESERVATIES

• To be in accord with good manufacturing
  practices, the use of preservatives
• Should not result in deception.
• Should not adversely affect the nutritive value
  of the food.
• Should not permit the growth of food-poisoning
  organisms while suppressing growth of the others
  that would make spoilage evident.

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• Chemical preservatives vegetables preservation
  are sulphur dioxide (SO2), benzoates, and
  sorbates.
• The efficiency of chemical preservatives depends
  primarily on the concentration of the
  preservative, the composition of the food, and
  the type of organisms to be inhibited.

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• The concentration of preservative permitted by
  food regulations.
• It is essential that the microbiological
  population of the food to be preserved is kept to
  a minimum by hygienic handling and processing.