Autolysis is the self-digestion process that occurs in fish after death. There are two main types of fish spoilage - bacterial and enzymatic. In some fish species like squid and herring, enzymatic changes caused by autolysis precede and dominate over bacterial spoilage when the fish are chilled. Autolysis contributes to quality loss in fish in addition to spoilage from microbes. The K-value index provides a measurement of freshness based on autolytic changes, with higher K-values indicating lower freshness levels.

1. AUTOLYSIS IN FISH

2. • No doubtly ,fish is a very nutritious food.
• It has also a charecteristic flavour which
attract the consumer.
• But when the fish is rotten than what????
• Every body know about the bad odor of fish.
• Sometimes our mother use the lemon leaves
to recover the bad odor of fish.

3. • Autolysis is the Self-digestion process
• There are at least two types of fish spoilage
– Bacterial
– Enzymatic
• In some species (squid, herring), the enzymatic changes precede
and therefore predominate the spoilage of chilled fish.
• In others, autolysis contributes to varying degrees to the overall
quality loss in addition to microbially-mediated processes.

4. Figure 1.1 Postmortem ATP degradation in fish muscle.

5. i. Atp-ase
ii. Myokinase
iii. Amp deaminase
iv. Imp phosphohydrolase
v. Nucleoside phosphorylase
vi. Inosine nucleosidase
vii. Xanthine oxidase.

7. • The K or "freshness" index gives a relative
freshness rating based primarily on the
autolytic changes which take place during post
mortem storage of the muscle. Thus, the
higher the K value, the lower the freshness
level

9. • Shortly after capture, chemical and biological
changes take place in dead fish due to enzymatic
breakdown of major fish molecules autolytic
enzymes reduced textural quality during early
stages of deterioration but did not produce the
characteristic spoilage off-odors and off-flavors.
• This indicates that autolytic degradation can limit
shelf-life and product quality even with relatively
low levels of spoilage organism