Initial loss of quality of fresh (non-preserved) lean or non-fatty fish species, chilled or not chilled, is caused by autolytic changes, while spoilage is mainly due to the action of bacteria. The initial flora on fish is very diverse, although most often dominated by Gram-negative psychrotrophic bacteria.
Freezing of fish has the advantage of providing the consumer with unprocessed fish that retain to a much greater extent the flavor, odor, appearance and texture of the freshly caught fish.
It also reduces deterioration caused by microorganism, enzyme, chemicals as O2. Many of the associated microbial cells are killed or damaged by freezing.
The presence of psychrotrophic organisms may be attributed to environmental contamination around the fish. Psychrotrophic bacteria are defined as able to grow when the temperature is lower than +7°C. Some psychrotrophic pathogens can grow in the refrigerated food with little or no obvious change of sensory characteristics.
Involved in food poisonings and responsible for alterations of the commercial quality of food-stuff, they make it necessary to limit the shelf life of chilled products. These psychrotrophic bacteria attack various substances in fish to produce metabolites, off-flavors and off-odor compounds
Generally, psychrotrophic bacteria may cause harmful health condition such as sepsis, diarrhea, meningitis, dysentery, food poisoning, urinary tract Infections and gastrointestinal infections .
Psychotropic bacteria in fish
