Table 1.

Types of spoilage, causes and main changes observed in spoiled fish.

Types of Fish Spoilage	Causes	Changes
Biological
➢Enzymatic	Glycolytic enzymes Autolytic enzymes Cathepsins Chymotrypsin, trypsin, carboxy-peptidases Calpain Collagenases Trimethylamine Oxide (TMAO) demethylase	Lactic acid production, flavour changes in fish flesh (nucleotide degradation), belly-bursting, colour change (black discoloration, yellowing of fish flesh, brown discoloration)
➢Microbial	Specific Spoilage Organisms (SSO) (Pseudomonas, Shewanella, Photobacterium, Acinetobacter, Aeromonas, Moraxella, H2S producing bacteria) Pathogenic bacteria: -Indigenous bacteria (Clostridium, Vibrio sp., etc.) -Non-indigenous bacteria (Salmonella sp., Escherichia coli, Shigella)	Loss of juiciness, firm texture, discolouration, and formation of ammonia-like off-flavours due to TMA production
Chemical	Oxidative rancidity	Rancid flavour and odour, texture changes
	Non- enzymatic oxidation	Discolouration