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1.3.3 Autolytic changes
Autolysis means “self-digestion”. It has been known for many years that there are at least two types of fish spoilage: enzymatic and bacterial.
Muscle enzymes and their activity: At the point of death, the supply of oxygen to the muscle tissue is interrupted because the blood is no longer pumped by the heart and is not circulated through the gills. Since no oxygen is available for normal respiration, the production of energy from ingested nutrients is greatly restricted. Figure illustrates the normal pathway for the production of muscle energy in most living teleost fish (bony finfish). Glycogen (stored carbohydrate) or fat is oxidized or “burned” by the tissue enzymes in a series of reactions which ultimately produce carbon dioxide (CO2), water and the energy-rich organic compound adenosine triphosphate (ATP). This type of respiration takes place in two stages: an anaerobic and an aerobic stage. The latter depends on the continued presence of oxygen (O2) which is only available from the circulatory system. Most crustaceans are capable of respiring outside the aquatic environment by absorption of atmospheric oxygen for limited period. |