Stabilizing pink salmon (Oncorhynchus gorbuscha) byproducts through modified silage processes

Authors: Bower, Cynthia; Hietala, Katie; Delaca, Theodore

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 2/27/2009
Publication Date: 10/20/2010
Citation: Bower, C.K., Hietala, K.A., Delaca, T.C. 2010. Stabilizing pink salmon (Oncorhynchus gorbuscha) byproducts through modified silage processes. Meeting Proceedings. In: P.J. Bechtel and S. Smiley (eds.), A Sustainable Future: Fish Processing Byproducts. Alaska Sea Grant, University of Alaska Fairbanks, pp. 207-219. doi:10.4027/sffpb.2010.17.

Interpretive Summary: Fish byproducts (such as heads, viscera, and frames) can create disposal issues for processors in Alaska. The most common method of preservation for these high-protein byproducts is through production of fish meal; however, less energy-intensive forms of stabilization exist. Acidification by lactic acid bacteria (LAB) is a relatively simple process for stabilizing fish, although a source of fermentable carbohydrate must be added. Potatoes are an agricultural product that might serve as a source of fermentable carbohydrate for preservation of fish. More than 18 million pounds of potatoes were grown in Alaska in 2006, with an estimated 20% loss. A cocktail of homofermentative LAB successfully grew in ground potato pulp without any additional nutrients, while sustaining a pH of 3.7 for 8 weeks. When LAB were added to a 1:1 mixture of potato and ground salmon heads, the pH dropped from 6.5 to 5.7 within 24 hours, but steadily increased to pH 6.5 over 8-weeks. Increasing the potato content of the potato-salmon mixture to 70% resulted in more acid production and was most effective (pH 5.9) when the salmon had been smoke-processed. Mixtures containing lower amounts of potato did not produce sufficient acidity to inhibit spoilage bacteria. Discarded agricultural products such as potatoes represent a potential source of fermentable carbohydrate for preservation of fish byproducts. These fermented fish products could serve as inexpensive feed sources for agricultural animals, supplements in aquaculture feeds, or as a local compost source for vegetable gardening or energy production.

Technical Abstract: Fish byproducts (such as heads, viscera, and frames) can create disposal issues for processors in Alaska. The most common method of preservation for these high-protein byproducts is through production of fish meal; however, less energy-intensive forms of stabilization exist. Acidification by lactic acid bacteria (LAB) is a relatively simple process for stabilizing fish, although a source of fermentable carbohydrate must be added. Potatoes are an agricultural product that might serve as a source of fermentable carbohydrate for preservation of fish. More than 18 million pounds of potatoes were grown in Alaska in 2006, with an estimated 20% loss. A cocktail of homofermentative LAB successfully grew in ground potato pulp without any additional nutrients, while sustaining a pH of 3.7 for 8 weeks. When LAB were added to a 1:1 mixture of potato and ground salmon heads, the pH dropped from 6.5 to 5.7 within 24 hours, but steadily increased to pH 6.5 over 8-weeks. Increasing the potato content of the potato-salmon mixture to 70% resulted in more acid production and was most effective (pH 5.9) when the salmon had been smoke-processed. Mixtures containing lower amounts of potato did not produce sufficient acidity to inhibit spoilage bacteria. Discarded agricultural products such as potatoes represent a potential source of fermentable carbohydrate for preservation of fish byproducts. These fermented fish products could serve as inexpensive feed sources for agricultural animals, supplements in aquaculture feeds, or as a local compost source for vegetable gardening or energy production.