Fish Microbiology and Quality Assurance (2+2)

Unit 2 - Growth and survival of microorganisms in food

2.2.4. Presence and activities of other microorganisms
The nature of microorganisms (microbial associations) encountered in foods can affect micro-flora of food which are called implicit factors. These include

• Properties of organisms present in food
• Response of these organisms to their environment
• Interaction with other organisms in food

Effect of activities of microorganisms on food micro-flora

• Among several organisms present in food, microorganisms which find condition suitable (in food) for growth dominate over other organisms. Ex. Molds can grow on dry fish, but slowly, than bacteria. In fresh fish bacteria overgrow molds as conditions are most favourable. Faster growing bacterial growth is inhibited by low a_w or low pH where moulds grow and cause spoilage.
• Some food borne microorganisms produce metabolite /substances such as antibiotics, bacteriocins, hydrogen peroxide, organic acids etc which are inhibitory /lethal to other microorganisms.
• Spoilage microorganisms can interact wherein growth of one favours the growth of others. Ex: In low a_w food (grain) growth of few molds increases aw leading to growth of other xerophilic molds.
• One organism may increase nutrient availability to others by degrading complex food substrates to simple forms.
• Some microorganisms may remove inhibitory substances thereby permit the growth of others.