Bacterial preservation of pink salmon using potatoes as a carbohydrate source

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

Submitted to: Journal of Food Processing and Preservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/22/2010
Publication Date: 12/20/2011
Citation: Bower, C.K., Hietala, K.A., Delaca, T.C. 2011. Bacterial preservation of pink salmon using potatoes as a carbohydrate source. Journal of Food Processing and Preservation. 35(6):822-831.

Interpretive Summary: Pink salmon byproducts, such as heads and viscera, create disposal issues for fish processors in Alaska. Fish meal is the common preservation method for processing wastes, but its production is costly. Other methods, including fermentation with lactic acid bacteria (LAB), are less energy intensive and relatively simple. However, natural acidification with LAB requires an added carbohydrate source, since fish tissues contain negligible amounts. For cool-weather locations, a possible source of fermentable carbohydrate is waste from the potato harvest. More than 18 million pounds of potatoes were grown in Alaska in 2006, with an estimated 20% loss. In this study, pink salmon heads (raw, smoked or cooked) were mixed with potatoes at different ratios and incubated for up to 60 days with LAB. An initial pH drop was observed, with concurrent production of lactic acid, for all salmon-potato silages within 24 hours; however, only silages composed of 100% potato or salmon with added sucrose became stable at pH 4.8 and remained at or below that pH for the duration of the study. Increasing the potato content of the potato-salmon silage increased the initial acidification, but did not prevent a rise in pH during storage. This study suggests that discarded agricultural products such as potatoes might be useful as a supplement for fermentation of fish byproducts, but these silages will still require a secondary carbohydrate source to achieve complete stabilization. Once preserved, fish processing waste offers an inexpensive feed source for agricultural animals, aquaculture feeds, or local compost for vegetable farming.

Technical Abstract: Pink salmon byproducts, such as heads and viscera, create disposal issues for fish processors in Alaska. Fish meal is the common preservation method for processing wastes, but its production is costly. Other methods, including fermentation with lactic acid bacteria (LAB), are less energy intensive and relatively simple. However, natural acidification with LAB requires an added carbohydrate source, since fish tissues contain negligible amounts. For cool-weather locations, a possible source of fermentable carbohydrate is waste from the potato harvest. More than 18 million pounds of potatoes were grown in Alaska in 2006, with an estimated 20% loss. In this study, pink salmon heads (raw, smoked or cooked) were mixed with potatoes at different ratios and incubated for up to 60 days with LAB. An initial pH drop was observed, with concurrent production of lactic acid, for all salmon-potato silages within 24 hours; however, only silages composed of 100% potato or salmon with added sucrose became stable at pH 4.8 and remained at or below that pH for the duration of the study. Increasing the potato content of the potato-salmon silage increased the initial acidification, but did not prevent a rise in pH during storage. This study suggests that discarded agricultural products such as potatoes might be useful as a supplement for fermentation of fish byproducts, but these silages will still require a secondary carbohydrate source to achieve complete stabilization. Once preserved, fish processing waste offers an inexpensive feed source for agricultural animals, aquaculture feeds, or local compost for vegetable farming.