DEVELOPMENT OF AGRICULTURALLY-DERIVED BIOPOLYMER COMPOSITES FOR NON-FOOD APPLICATIONS
Location: Bioproduct Chemistry and Engineering Research
Title: RHEOLOGICAL AND MECHANICAL PROPERTIES OF CROSS-LINKED FISH GELATINS
Submitted to: Polymer Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 3, 2006
Publication Date: July 26, 2006
Citation: Chiou, B., Avena Bustillos, R.D., Shey, J., Yee, E., Bechtel, P.J., Imam, S.H., Glenn, G.M., Orts, W.J. 2006. Rheological and mechanical properties of cross-linked fish gelatins. Polymer. 47(18):6379-6386.
Interpretive Summary: We extracted gelatin from the skins of Alaska pollock and Alaska pink salmon, which comprise about two-thirds of the annual Alaskan marine finfish catch. It has been estimated that over a million tons of fish by-products are generated each year from the Alaskan fishing industry. Of these, approximately 60 percent are dumped back into the ocean. The by-products include substantial quantities of fish skin, which is a good source of fish gelatin. We added two cross-linkers, glutaraldehyde and genipin, to the fish gelatin to improve their mechanical properties at room temperature. We also examined a commercial porcine gelatin as a comparison. We varied sample pH, cross-linker concentration, and temperature and monitored gelatin cross-linking by using dynamic rheology. The fish gelatins showed faster cross-linking at higher pH, higher cross-linker concentration, and higher temperature. In addition, we measured gel strength of the cross-linked gelatin samples. Porcine gelatin samples had much greater gel strengths than fish gelatin samples.
Gelatin was extracted from the skins of Alaska pollock (Theragra chalcogramma) and Alaska pink salmon (Oncorhynchus gorbuscha). Amino acid analysis and gel electrophoresis were used to determine their amino acid composition and molecular weight profiles, respectively. Dynamic rheology was also used to characterize the fish gelatins’ gelation and melting behavior as well as their cross-linking behavior upon adding genipin and glutaraldehyde. Pollock and salmon gelatin had lower gelation and melting temperatures than that of a commercial porcine gelatin. Both fish gelatins that contained genipin showed faster cross-linking rates for samples with higher pH values. However, salmon samples exhibited greater dependence on pH. Also, pollock gelatin cross-linked faster with glutaraldehyde than with genipin. After five days of cross-linking, all porcine samples had much greater gel strengths than pollock samples. In addition, porcine samples containing genipin had gel strengths several times greater than those containing glutaraldehyde.