Fish Processing and Bycatch Management

Bycatch and Seafood Processing Waste

• Bycatch: consists of other fish species, undersized or juvenile species, or targeted species of different sizes
• Bycatch can be used as raw material in fish silage production
• Seafood processing waste includes trimmings such as fish heads, skin, tails, and fins, as well as shells and heads of shrimp and other crustaceans
• Non-utilizable waste materials can be used in making fish silage

Non-Commercially Important, Non-Indigenous Species

• non-indigenous species introduced in some bodies of water in the Philippines and elsewhere
• These species can cause environmental harm and endanger native populations
• Research has been conducted on using these species as ingredients in fishmeal and fish silage production

Fish Silage Production

• Samples for analysis should be taken after thorough mixing to ensure representativeness
• Acidity should be measured, with a target pH of 3.6-4 using formic acid
• Fish silage with correct acidity can be stored at room temperature for at least two years without putrefaction
• Silage becomes smoother in consistency during storage and develops a pleasant malty odor

Fish Protein Concentrate

• Fish protein concentrates (FPC) are produced by extracting and separating proteins from raw material using chemical solvents and high temperatures
• FPC can be used as a human food ingredient
• Solvent-extracted FPC (type-A FPC) is produced using isopropanol or azeotropic extraction with ethylene dichloride
• The final supernatant fraction should be largely colorless and odorless, consisting primarily of protein

Fish Protein Concentrate

• Fish protein concentrates (FPC) are produced by extracting and separating proteins from raw materials using chemical solvents and high temperatures.
• The National Marine Fisheries Service (NMFS) initiated a research program in the 1960s to produce FPC on a large scale to stimulate the US seafood industry and address global protein malnutrition.
• Solvent-extracted FPC (type-A FPC) is produced using isopropanol or azeotropic extraction with ethylene dichloride.
• The process involves grinding and extracting with isopropanol at 20-30°C for 50 minutes, followed by two more extractions with isopropanol and azeotropic isopropanol.
• The final product is largely colorless, odorless, and primarily consists of protein.

Fish Silage

• Fish silage is a liquid product made from whole fish or parts of fish liquefied by enzymes in the presence of an added acid.
• Enzymes break down fish proteins into smaller soluble units, while the acid helps speed up the process and prevent bacterial spoilage.
• Fish silage can be made from white fish offal, which contains little oil, or from fatty fish like herring, which requires oil removal.
• The composition of fish silage is similar to the raw material, typically consisting of 80% water, 15% protein, 4.5% ash, and 0.5% fat.

Silage Production

• Acids used in silage production include hydrochloric acid, sulphuric acid, and formic acid, which is an organic acid with bacteriostatic action.
• Formic acid is more expensive than mineral acids but allows for preservation at a slightly higher pH and does not require neutralization before use.

Raw Materials for Fish Silage Production

• Fish silage can be made from underutilized species, bycatch, or seafood processing waste, which would otherwise be discarded and contribute to environmental problems.
• Non-commercially important, non-indigenous species can also be utilized in fish silage production, making them more useful and reducing their environmental impact.