Fish Processing, Preservation and Value Addition
Fish Processing, Preservation and Value Addition
This domain tests spoilage, cold chain, traditional preservation, and product development. The exam expects you to link a process to shelf life and safety.
Core rules
- Spoilage begins with rigor mortis and ATP breakdown; hypoxanthine and TVB-N rise as fish spoils. Scombroid fish can form histamine if held warm.
- Chilling at 0–4 °C slows bacterial growth; freezing at −18 °C or colder stops growth but does not sterilise.
- Drying reduces water activity; salting draws water out of tissue; smoking combines drying, heat, and antimicrobial smoke compounds.
- Canning uses a sealed retort process; low-acid fish requires sufficient heat treatment to destroy Clostridium botulinum spores.
- Value addition includes fillets, fish pickle, cutlet, surimi, and dried snack products.
Worked example
A processor has 20 kg of fish and wants a 20% salt cure. Salt needed = 20 kg × 0.20 = 4 kg. If the final product is 18 kg after draining, the salt content is roughly 4 ÷ 18 × 100 = 22% of product weight. That is a high-salt product; it must be labelled and stored dry to prevent mould.
Traps
Do not claim freezing kills all bacteria; do not thaw fish on a warm bench; do not assume cooking destroys histamine; and do not confuse drying with smoking.