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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: Dehydration of pollock skins prior to gelatin production

Authors
item Bower, Cynthia
item Avena Bustillos, Roberto
item Hietala, Katie
item Bilbao-Sainz, Cristina
item Olsen, Carl
item McHugh, Tara

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: February 10, 2009
Publication Date: N/A

Technical Abstract: Alaska pollock (Theragra chalcogramma) is the USA’s largest commercial fishery, with an annual catch of over one million tons. During processing the pollock skins are typically discarded, despite their high value for gelatin production. Hot-air drying is an effective method for decreasing the moisture content of fish skins, but it is costly. This study evaluated a less energy-intensive technology, the use of food-safe desiccants for reducing water weight in pollock skins prior to shipment. Additionally, gelatins were prepared from each treatment to ensure that functional properties of the skins were not damaged during desiccation. Pollock skins were dried for 24 h using four different moisture-adsorbing agents: silicon dioxide, calcium bentonite, calcium sulfate, and sodium chloride. The lowest moisture levels (6.9%) were found in skins dried using calcium sulfate, whereas sodium chloride “salted” skins had the highest residual moisture (47%). When gelatins were extracted from the dried skins, recoveries were approximately 17%, although pollock skins treated with sodium chloride had significantly lower yields (9%). Gelatin solutions revealed similar pH and clarities among treatments except for gelatin made from pollock skins treated with sodium chloride, which displayed reduced clarity. There were no major differences in gelling temperature among treatments, although slightly reduced gel strengths were apparent. When the gels were cast into films, water vapor permeability results were similar for all treatment groups except salted skins, which had a higher (less desirable) permeability. Gelatin film strength was generally retained regardless of desiccant type. Elasticity was actually found to be superior in gelatin films prepared from calcium sulfate and calcium bentonite treated pollock skins due to calcium crosslinkage. The use of food-safe, heat regenerable desiccants offers many advantages for stabilizing perishable commodities. By reducing the weight of water in pollock skins, transportation costs can be decreased during shipment to a gelatin processing facility.

Last Modified: 4/20/2014
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