Fish products and Byproducts Technology

Unit 7 - Fish protein concentrate

7.2. Methods used for preparation of Fish Protein Concentrate
Numbers of processes including enzymatic hydrolysis have been developed for preparation of FPC. The most popular ones employ some organic solvent to remove lipids and water from the raw or cooked fish meat. Commonly employed methods are

• Viobin Process
• Canadian process
• Azeotropic extraction method

Viobin Process
In this process, simultaneous dehydration and removal of lipids from ground whole fish is carried out using ethylene chloride. Ground fish is subjected to ethylene chloride treatment and the mass is then heated to boiling with indirect steam. Ethylene chloride forms a constant boiling mixture with boiling at 71° C. On condensation, the azeotropic mixture separates into two layers. The solvent layer is pumped back into the vessel to carry off more water. As the water content approaches zero the temperature of boiling will approach that of solvent indicating the completion of the process. Lipids will remain in the vessel in residual solvent. It is filtered off and the residue is washed once or twice with fresh solvent and then heated in a steam jacketed vessel under vacuum to remove as much as solvent as possible. Finally, vessel is flushed with dry steam to remove the last traces of solvent. The dry product is then pulverised and bagged.
Canadian process
It employs iso-propanol as a solvent for lipid extraction. It involves two stages. First stage involves grinding the fish, its suspension in water acidified with phosphoric acid (pH 5.5) and coking for 30 minutes at 70-80 °C with constant stirring followed by filtration of cooked mass and repeated washing with hot water until it becomes odourless. The residue from first stage is then suspended in iso-propanol and refluxed for 15 minutes. The solvent is removed by filtration and the residue is further treated with solvent to reduce lipids and water. The residue after final treatment is pressed and the press cake is dried and pulverised. The residual solvent is removed under vacuum.
Azeotropic extraction method
It is used in India where azeotropic mixture of hexane and ethyl alcohol is used as solvent. Minced whole fish is cooked in boiling water containing 0.5% acetic acid for 30 minutes. The solid matter is pressed well after draining off the liquid and is refluxed under constant stirring for 30 minutes with azeotropic mixture of hexane and ethyl alcohol containing 32.3 moles percent alcohol boiling at 58.68°C. The solid matter is refluxed again with fresh solvent mixture. The solvent is drained off and after distilling of the remaining solvent the extracted mass is steam-stripped under reduced pressure to drive off the remaining traces of the solvent. The mass is then pulverised to a fine mesh size.
Other methods of preparation of FPC
British process employs ethyl alcohol. Chilean process employs hexane followed by ethyl alcohol. The Moroccan process employs a mixture of solvents which include hexane, ethyl acetate and isopropyl alcohol.