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United States Department of Agriculture

Agricultural Research Service

Research Project: CONVERTING ALASKA FISH BY-PRODUCTS INTO VALUE ADDED INGREDIENTS AND PRODUCTS Title: Sustainability through increased utilization of Alaska's fish and agricultural by-products

Authors
item Bower, Cynthia
item Hietala, Katie
item Delaca, Theodore

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: August 29, 2008
Publication Date: N/A

Interpretive Summary: Alaska salmon by-products, (such as heads, viscera, and frames), were estimated at 110,000 metric tons of waste in 2005, creating major disposal issues for fish processors. Discarded salmon tissues are currently receiving attention as an underutilized source of protein and omega-3 fatty acids. However, the seasonality and remote locations of the harvest require feasible methods to ensure that these high-value by-products are not wasted. By-products preserved through anaerobic fermentation with lactic acid bacteria (LAB) could find use as an inexpensive feed source for agriculture and aquaculture feeds, or as a nutrient-rich fertilizer for vegetable gardening. However, fish contain only negligible amounts of carbohydrate and would therefore require an outside source for effective LAB fermentation. This study examined the use of Alaska potatoes as a carbohydrate source for LAB fermentation of heads from pink salmon. The potato industry in Alaska produced over 18 million lbs of potatoes in 2006, with an estimated 20% loss. This waste product may serve as a convenient source of fermentable carbohydrate for preservation of salmon by-products. Preliminary studies indicated that a cocktail of homofermentative LAB were capable of growing in ground potato pulp without any additional nutrients, while sustaining a pH of 3.7 for up to 8 weeks. In this study, pink salmon heads from Kodiak, AK and potatoes from Palmer, AK were ground and mixed together to determine if the potatoes could serve as a carbohydrate source for LAB-fermentation of salmon heads. The pH dropped from 6.5 to 5.7 within 24 hrs using a 1:1 mixture of potato:salmon, although there was a steady increase to pH 6.5 through the 8-week incubation. Increasing the potato content of the potato:salmon mixture to 7:3 facilitated a decrease in pH from 6.3 to 4.6 within 24 hrs, with an increase to pH 4.9 by 120 hrs, remaining steady for up to 10 weeks. For mixtures containing lower ratios of potato:salmon, the pH did not decrease to an adequate level of acidity to inhibit food spoilage bacteria. When sucrose was added as the carbohydrate source, instead of potatoes, the pH of the ground salmon heads decreased to 4.5 and remained steady for up to 8 weeks. Current studies are looking at quantification of lactic acid and LAB growth during ensilage of potato-salmon mixtures.

Technical Abstract: Alaska salmon by-products, (such as heads, viscera, and frames), were estimated at 110,000 metric tons of waste in 2005, creating major disposal issues for fish processors. Discarded salmon tissues are currently receiving attention as an underutilized source of protein and omega-3 fatty acids. However, the seasonality and remote locations of the harvest require feasible methods to ensure that these high-value by-products are not wasted. By-products preserved through anaerobic fermentation with lactic acid bacteria (LAB) could find use as an inexpensive feed source for agriculture and aquaculture feeds, or as a nutrient-rich fertilizer for vegetable gardening. However, fish contain only negligible amounts of carbohydrate and would therefore require an outside source for effective LAB fermentation. This study examined the use of Alaska potatoes as a carbohydrate source for LAB fermentation of heads from pink salmon (Oncorhynchus gorbuscha). The potato industry in Alaska produced over 18 million lbs of potatoes in 2006, with an estimated 20% loss. This waste product may serve as a convenient source of fermentable carbohydrate for preservation of salmon by-products. Preliminary studies indicated that a cocktail of homofermentative LAB were capable of growing in ground potato pulp without any additional nutrients, while sustaining a pH of 3.7 for up to 8 weeks. In this study, pink salmon heads from Kodiak, AK and potatoes from Palmer, AK were ground and mixed together to determine if the potatoes could serve as a carbohydrate source for LAB-fermentation of salmon heads. The pH dropped from 6.5 to 5.7 within 24 hrs using a 1:1 mixture of potato:salmon, although there was a steady increase to pH 6.5 through the 8-week incubation. Increasing the potato content of the potato:salmon mixture to 7:3 facilitated a decrease in pH from 6.3 to 4.6 within 24 hrs, with an increase to pH 4.9 by 120 hrs, remaining steady for up to 10 weeks. For mixtures containing lower ratios of potato:salmon, the pH did not decrease to an adequate level of acidity to inhibit food spoilage bacteria. When sucrose was added as the carbohydrate source, instead of potatoes, the pH of the ground salmon heads decreased to 4.5 and remained steady for up to 8 weeks. Current studies are looking at quantification of lactic acid and LAB growth during ensilage of potato-salmon mixtures.

Last Modified: 4/20/2014
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