Fish products and Byproducts Technology

Unit 5- Hurdle technology in fish preservation

5.2.2. Types of fish marinades
• Cold marinades
• Cooked marinades
• Fried marinades
Cold marinades: Raw fish is preserved in a mixture of acetic acid and 10% salt at an optimum pH of 4.5. At no stage during the process the fish is heated. Bacterial and autolytic activities occur, and hence and shelf life is very limited at ambient temperatures.
Cooked marinades: The fish is placed in a hot solution of 1-2% acetic acid and salt at about 85oC. Here most of the bacteria are killed and the enzymes are inactivated or denatured. Shelf life is also of a longer duration.
Fried marinades: Here the fish are fried for 15-20 minutes in fat before packing in brine containing 2-3.5% acetic acid and 3-5% salt. Frying kills most of the bacteria and denatures the enzymes.
Marinades in general are stable only for a limited period. Shelf stability depends on storage temperature and on type of bacteria present. Spoilage in cold marinades is indicated by gas formation, in cooked marinades it is by gas formation and liquefaction and in fried marinades it is by gas formation and appearance of slime. The causative organisms for spoilage are hetero fermentative lactic bacteria in cold marinades, proteolytic bacteria in cooked marinades and slime formers in fried marinades.