FOOD SPOILAGE

Spoilage may be defined as deterioration, which leads to undesirable changes in the organoleptic characteristics of food. These are adverse changes that are largely attributable to biological factures.

 Deterioration leads to changes in food quality induced by physical, chemical and biochemical reactions occurring within the food. Spoilt food may have the following characteristics.

• v  An offensive smell
• v  A moldy surface
• v  A sharp flavor
• v  A changed color
• v  A slimy surface
• v  A strong sour flavor
• v  Gas development (production of gas).
  
  
  

Causes of food spoilage

• v  Microorganisms such as yeasts, moulds and bacteria may cause spoilage in foods.
• v  Physiological life processes such as chemical reactions within the food (which may be enzyme catalyzed)
• v  Attack by insects and rodents, which consume the food/feedstuff and contaminate the rest with their excreta.
• v  Cold temperature and uncontrolled freezing may induce "freeze burns" which make food undesirable.
• v  Sensitivity to light is another source of food spoilage. Certain nutrients in food are sensitive to various types of radiation. Exposure to such radiation not only leads to loss of nutrients but also initiates reactions that accelerate deterioration.
• v  Humidity
• v  Oxygen

 

The Nature of Microorganisms Involved in the Spoilage of Foods Bacteria (Class Schizomyeetes)

Bacteria are small single celled organisms. They may be spherical, rod like, or branched. Their cells may be united into filaments. They may be motile, non-motile, aerobic or anaerobic. Chromatin granules represent the nucleus in bacteria. The cell wall is made up of chitin, proteins and carbohydrates. Some forms also have flagella. The flagella of the motile bacteria usually originate from the cytoplasm. Inside the cell wall, there is a thin plasma membrane. The cytoplasm contains many small vacuoles, stored food granules such as volutin, glycogen and fats, sometimes sulfur.

The classification of bacteria has been revolutionized by molecular genetics. Sometimes molecular genetics is still used in combination with the older methods such as cell wall analysis and serological profiles. Some of the new methods based on molecular genetics are:

 

v  DNA homology and the guanine + cytosine (purine bases found in the DNA molecule) content.

v  Similarities in the sedimentation pattern of the ribosomal RNA molecule.

v  The nature of oligonucleotides present.

v  Soluble proteins.

v  Morphological and biochemical characteristics.

v  Cellular fatty acids.