Fish Microbiology and Quality Assurance

Unit 1 - Role and significance of microorganisms in food

1.6 Significance of microorganisms in foods
Microorganisms associated with food derive energy from food for those cell growth, maintenance and reproduction. Based on their function microorganisms associated with foods may be divided in to three general groups;

• Those causing spoilage or undesirable changes in the food
• Those producing desirable changes
• Those producing disease

Based on the extent of stability to microbial invasion foods may be classified as;

• Perishable foods Ex. Fish and meat
• Semi-perishable foods Ex. Potatoes. Tomato
• Stable foods Ex. Cereals, Flour and Sugar

The stable or semi-stable foods become unstable or perishable when the moisture content increases.

Factors affecting microorganisms in foods
The survival and activity of microorganisms in foods depends on several factors namely, numbers and types of microorganisms present, type of food, treatments to which the food has been exposed, processing or storage treatments that the food receives, whether the food is to be consumed as it is or heated.

The food associated microorganisms may have useful function, cause spoilage, cause health hazard and play no role or remain inert. The cases of spoilage, food-borne illnesses or useful activity results due to the growth and multiplication of the microorganisms. The inert microorganisms are those which do not find food environment favorable for their growth, and remain dormant without causing any changes in food.

Causes for spoilage of food
Spoilage of food usually occurs due to,

• Undesirable changes brought about by the microorganisms in the odour, colour, taste, texture and appearance of the food.
• Some microorganisms may not directly involve in spoilage but bring about changes in food that will facilitate growth of spoilage organisms. Ex. Bacteriophage attacking useful organisms and facilitating growth of undesirable organisms leading to spoilage.

Useful organisms are those which by their activity or fermentation reactions facilitated by the microbial enzymes produce desirable changes in food (Ex. bakery, dairy, wine industries).