Ilgin Paker

Date of Graduation

2015

Document Type

Dissertation

Degree Type

PhD

College

Davis College of Agriculture, Natural Resources and Design

Department

Wildlife and Fisheries Resources

Committee Chair

Kristen E Matak

Committee Co-Chair

Jacek Jaczynski

Committee Member

Litha Sivanandan

Committee Member

Janet C Tou

Committee Member

Jianbo Yao

Abstract

Utilization of aquatic resources has rapidly gained importance. Traditional fish processing does not utilize the majority of the fish, thus generating large quantities of waste that impacts the economy, sustainability and environmental stress adversely. Protein can be extracted from underutilized sources such as silver carp and catfish using a pH shift processing method and incorporated into the human diet. Therefore, myofibrillar proteins were extracted from ground fish using different alkali solubilization and precipitation strategies. The efficacy of protein separation from lipids, and insoluble such as skin, fins, scales and bones were investigated and compared. Protein and lipid recovery yields were calculated to determine the economic feasibility of the procedure by calculating the amount of material recovered out of the available protein or lipids present in the initial material. Mineral content of the recovered protein was analyzed and compared to the initial fish and Alaska Pollock surimi.;Although every factor such as solubilization pH, base, and acid as well as their interactions had a significant effect on the results, effect of processing base was more evident for protein separation. Protein solubility was significantly increased (p<0.05) when calcium hydroxide (Ca(OH)2) was used compared to sodium hydroxide (NaOH). Therefore, protein concentration was also greater (p<0.05) with lower amount of impurities such as lipids and ash when Ca(OH)2 was used as the processing base compared to NaOH at every solubilization pH (11.0, 11.5, 12.0, 12.3) tested in this study.;The recovered protein was then made into protein gels in order to investigate gelation conditions. Fish muscle protein mainly consisting of myosin and actin cross-link and form a gel network upon heating. Yet, the efficiency of gel setting period that allows for the crosslinking to take place depends on a variety of factors mainly impacted by time and temperature. Protein gel texture and color is also affected by post cooking storage. Therefore, widely applied pre-cooking gelation time and temperature strategies, and post-cooking period on texture and color of final protein gels was investigated. Four most commonly applied pre-cooking gelation strategies (no-setting time, 30 min at 25°C, 1 h at 40°C, or 24 h at 4°C) were applied to protein pastes (fish protein concentrate and standard functional additives). After cooking, texture and color were either analyzed directly or after 24 h at 4°C on gels adjusted to room temperature.;Gelation properties as well as protein amount in the recovered protein gels can be changed by salvaging water soluble sarcoplasmic proteins from fish processing water or solution and incorporating them into myofibrillar protein gels. Therefore, sarcoplasmic proteins of silver carp were solubilized and added back to recovered myofibrillar protein or Alaska Pollock in solution form to investigate the impact on texture and color of protein gels. Sarcoplasmic protein amounts tested (77 or 144 mg/kg paste) yielded softer, less gummy, chewy, cohesive and resilient (p<0.05) gels compared gels containing transglutaminase, an exogenous enzyme. In order to investigate the effects of greater amounts of sarcoplasmic proteins in the myofibrillar protein gels, solubilized sarcoplasmic proteins were concentrated, made into a powder using a freeze-dryer and added back into recovered protein gels.;A separate study investigating the effects of starch addition at increasing amounts (0, 5, 10, 15, 20 g/kg paste) determined that most of the textural attributes such as hardness, gumminess, chewiness, firmness and resistance to deformation were higher (p<0.05) for gels containing starch; however, these attributes did not increase with the increasing starch concentration. Therefore, the similar textural properties observed in 23 g/kg paste sarcoplasmic protein containing gels without starch or polyphosphates and gels developed using 5 transglutaminase/kg paste, 15 g starch/kg paste and 3 g polyphosphates/kg paste can be attributed to the gel strengthening properties of high amounts of sarcoplasmic proteins in calcium enhanced myofibrillar protein gels.;Overall, this research shows that Ca(OH)2 is effective in protein solubility and separates proteins from other fractions such as lipids and insolubles when used as a processing base during pH shifts. Ca(OH) 2 solubilization yields a recovered protein fraction enhanced with calcium, and lowered sodium. Therefore, protein recovered using Ca(OH)2 will yield a naturally whiter end product with a more beneficial content. Protein gels made from calcium enhanced protein will be harder and naturally whiter. Moreover, sarcoplasmic protein recovered using simple solubilization steps from fish and by-products may be used as a nutritional supplement to enhance protein content of food products or can be incorporated into functional food products such as protein gels containing lower amounts of sodium. (Abstract shortened by UMI.).

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