Semester

Spring

Date of Graduation

2012

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Animal and Nutritional Sciences

Committee Chair

Kristen E Matak

Committee Co-Chair

Jacek Jaczynski

Committee Member

Jianbo Yao

Abstract

Silver carp (Hypophthalmichthys molitrix) is one of the main freshwater fish species with a high nutritional value; however, it is hard to process the fish due to its boney carcass. Therefore, isoelectric solubilization and precipitation (ISP) processing was applied to headed gutted silver carp to separate the protein from the bones, scales, skin, fins, etc. Different solubilization strategies (pH 2.5, 3.0. 11.5 and 12.0) using organic acids, either acetic acid (AA) or a 30% formic and lactic acid combination (F&L), were applied during ISP and the different effects of treatments on the materials recovered from the initial silver carp were compared. The recovered carp proteins were then used to make protein gels similar to surimi with the use of standard food additives. To further assess the effect of using different solubilization pH values and organic acids on the protein quality of the recovered fractions, the functional, texture and color properties were analyzed.;Proximate composition of the recovered proteins showed that processing at basic pH using AA was most effective at removing impurities (i.e. bones, scales, skin, fins) (p<0.05) and the impurities were effectively removed from recovered lipids regardless of processing pH or acid type. Functional properties of gels made from protein recovered by ISP processing using organic acids as the processing acid had typical gelation characteristics. Moreover, it was seen that isoelectrically recovered carp proteins were not denatured and retained functionality. Thermal denaturation and dynamic rheology of the protein gels revealed that using AA under acidic conditions and F&L with alkali treatments yielded improved gel structure. In addition to that, color analysis presented data showing that gels made using F&L were whiter for all solubilization conditions (p<0.05) and were similar to the whiteness of Alaska Pollock surimi gels under acidic treatments. Texture analyses highlighted that gels made from protein solubilized at basic pH values had firmer texture (p<0.05) and were harder and more cohesive, gummy and chewy (p<0.05) than proteins solubilized under acidic conditions. Moreover, gels made from proteins recovered using AA as the processing acid under basic conditions had similar shear stress responses as Alaska Pollock surimi.;This research shows that organic acids have the potential to recover protein and lipid from otherwise hard to process fish by ISP processing. The gels made from recovered carp protein show similar or improved functional, texture and color properties compared to Alaska Pollock surimi depending on the treatment and might be used for the development of restructured fish products for human consumption.

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