Microbial Grouping

Microbial Grouping
The microbial groups important in foods consist of several species and types of bacteria, yeasts, molds and viruses. Bacteria, yeasts, molds and viruses are important in food for their ability to cause foodborne diseases and food spoilage to produce food and food ingredients.

Many bacterial species and some molds and viruses, but not yeasts are able to cause foodborne disease.

Most bacteria, molds and yeasts, because of their ability to grow in foods (viruses cannot grow in foods, can potentially cause food spoilage.

Several species of bacteria, molds and yeasts are considered safe of food grade or both and are used to produce fermented foods and food ingredients.

Among the four major groups, bacteria constitute the largest group. Because of their ubiquitous presence and rapid growth rate even under condition where yeast and molds cannot grow, they are considered the most important in food spoilage and foodborne disease.

Prion or proteinaceous infectious a particles have been identified to cause transmissible spongiform encephalopathies (TSEs) in humans and animals.
Microbial Grouping

Food Spoilage

Food Spoilage
Processed and natural foods are composed mainly of carbohydrates proteins and fats.

The major constituents in vegetables and fruits are carbohydrates, including sugars (sucrose, etc), polymers of sugars (starch) and other complex carbohydrates such as fibers.

Fats are the major components of milk and most cheeses, and proteins are the chief constituents of muscle foods.

Under natural storage conditions, foods start to deteriorate once the living cells in the foods (plant and animal origins) are dead.

Either when the cells are dead or if the tissues are damaged, deterioration begins with the secretion of internal proteases (such as chymotrypsin and trypsin to break up proteins at specific amino acid positions), lipases and lyases from lyzosomes to disintegrate the cells, to hydrolyze proteins into amino acids and starch into simpler sugars (or monosaccharides), and to de-esterificate fats ( triglycerides) into fatty acids.

The exposure of foods and damaged cells to the environment attracts microorganisms (e.g. bacteria, molds and virus) and insects, which in turn further accelerate the decomposition of the food.

For most food poisoning, spoilage has not reached the stage where the sensory attributes (appearance, smell, taste, texture, etc.) of the food are abnormal.

Illness form food can be mainly classified as:

• Food borne infection caused by pathogenic bacteria (disease-causing microorganisms, such as Salmonella bacteria, multiplying in victim’s digestive tract causing diarrhea, vomiting and fever, etc.)
  
• Food borne intoxication (food poisoning resulting from toxin produced by pathogenic microorganisms, e.g. Clostridium botulinum and Staphylococcus aureus, in the digestive tract).
  

Food borne illness also has a major economic impact on society, costing billions of dollars each year in the form of medical bills, lost work time, and reduced productivity.
Food Spoilage