*Enzymatic autolysis (reactions caused by the activities of the fish’s own enzymes)
*Oxidation (oxidation of unsaturated lipids)
*Microbial growth (metabolic activities of microorganisms)
One-fourth of the world's fish supply and 30% of landed fish are lost through microbial activity alone.
Fresh fish spoilage can be very rapid after it is caught. The spoilage process (Rigor mortis) will start within 12 h of their catch in the high ambient temperatures of the tropics.
Spoilage of fish can be considered as any change that render the product unacceptable for human consumption. When fish dies, the biochemical changes responsible for anabolism stop. As an inevitable consequence of this process of cessation of anabolism, catabolism starts bringing spoilage to fish flesh. The digestive enzymes still being active, instead of acting on the food present inside the gut, begin to digest tissue components such as lipids, carbohydrates and proteins. This process is called “autolysis”.
One important action determining the onset of spoilage in freshly caught fish is rigor mortis, the stiffening of the body. Usually, this develops within 1-7 hours after death. Rigor mortis sets in and passes quickly in very active fish but slowly in inert fish.
Characteristics of spoiled fish
*The flesh is soft to touch. When the flesh is pressed it leaves a permanent indentation.
*The skin looks dull and has slime on the surface.
*The gills look brownish.
*It gives a bad smell.
With the ever-growing world population and the need to store and transport the food from one place to another where it is needed, food preservation becomes necessary in order to increase its shelf life and maintain its nutritional value, texture and flavour.
Spoilage of fish: Definition and characteristics
