Progress 10/01/07 to 09/30/08
Outputs
OUTPUTS: 1) Experiments were performed to further investigate production of functional fish protein ingredients from byproducts and their influence on fish muscle structure, appearance, water holding, oxidative rancidity, consumer acceptance and fresh/frozen shelf life. 2) Outcomes of this research were presented to industry representatives and also at international conferences. 3) Outcomes of this research was tested at select seafood processors, to demonstrate value addition 4) Results were disseminated to industry by presentations and in-house demonstrations, nationally and internationally. 5. Results were disseminated to industry and academia by presentations at international conferences PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Fish and meat product processors, food ingredient processors, food science researchers PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Variations of the pH-shift process (low/high pH solubilization followed by isoelectric precipitation) were used to produce different functional protein ingredients. Protein ingredients produced using the acid-aided process were less functional than ingredients produced using the alkali-aided process. This was found to be due to more protein denaturation from the acid-aided process. The protein ingredients produced using the acid-aided process were also more oxidatively unstable and of darker color due to more retention of heme proteins. These findings led us to use the alkaline-aided pH-shift process to produce functional protein ingredients to be further investigated. Different species of fish, crustaceans and mollusks were treated with suspended protein ingredients (under various different solution conditions) with injection (fish), soaking or tumbling (crustaceans/mollusks) to different uptake levels. Common commercial ingredients were tested for comparison. The products were then subjected to both fresh and frozen storage. The products were analyzed for microbial stability, oxidative stability, water holding, color, muscle texture and sensory analysis. The pH-shift process dramatically reduced the microbial count of the protein ingredients compared to the raw material they were produced from. The microbial shelf life of the treated products was very similar to untreated products, demonstrating that injection or tumbling did not create microbial problems under the conditions tested. The color of treated products was very similar to untreated products, and was more "natural" compared to some of the other ingredients tested, particularly compared to salt and phosphate which left a more translucent and glossy appearance. Seafoods treated with protein suspensions had equal to higher oxidative stability than untreated fillets, based on analysis of lipid hydroperoxides and thiobarbituric acid reactive substances. Further enzymatically treating the protein ingredients and incorporating them into the seafoods increased oxidative stability. Results demonstrated that the protein ingredients had anti-oxidative properties. Seafoods treated with protein suspensions were more cohesive than untreated fillets and had significantly higher water holding (based on thaw loss, drip loss, cook loss and centrifugal methods) leading to a more moist and tender product. Sensory testing revealed an overall preference of seafoods treated with protein suspensions compared to untreated products. This project is expected to not only lead to better utilization of seafood byproducts, but also lead to the development of fish proteins as commercial and competitive ingredients for water control in seafood products and quality improvement of seafood products. Improvements in water-holding capacity should lead to improvements of US seafood products since products will be more palatable as well as more nutritious since more nutrients are retained as less water is lost. Furthermore more retained water in seafood product is expected to significantly improve the bottom line of the seafood processors and make them more competitive not only on a local but on a global scale.
Publications
- Thorkelsson, G., Slizyte, R., Gildberg, A., Kristinsson, H. G. 2008. Fish proteins and peptides. In: Processing methods, quality and functionality (Marifunc). Wageningen, Holland; Wageningen University Press; In Press (50%)
- Raghavan, S and Kristinsson, H.G. 2008. Hydrolysates from alkali treated tilapia protein isolates as natural antioxidants. Annual Meeting of the Institute of Food Technologists, New Orleans, LA. Abstract 007-13 (50%)
- Raghavan, S., Kristinsson, H.G and Hamaguchi, P. 2008. Antioxidant activity of alkali-treated tilapia protein hydrolysates and its different fractions. 8th Joint Meeting of the Seafood Science and Technology Society and Atlantic Fisheries Technology Conference. Wrightsville Beach, North Carolina. (25%)
- Raghavan, S and Kristinsson, H.G. 2008. Inhibitory activity of tilapia protein hydrolysates in human mononuclear cells. 8th Joint Meeting of the Seafood Science and Technology Society and Atlantic Fisheries Technology Conference. Wrightsville Beach, North Carolina. (25%)
- Davenport, M.P. 2008. Structure/function relationship of Channel catfish (Ictalurus punctatus) muscle proteins subjected to pH-shift processing.
- Theodore, A.E., Raghavan, S. and Kristinsson, H.G. 2008. Antioxidative activity of protein hydrolysates prepared from alkaline-aided channel catfish protein isolates. J. Agric. Food Chem. 56 (16), 7459-7466 (50%)
- Raghavan, S., Kristinsson, H.G. and Leeuwenburgh, C. 2008. Radical scavenging and reducing ability of tilapia (Oreochromis niloticus) protein hydrolysates. J. Agric. Food Chem. 56, 7459-7466. (25%)
- Raghavan, S. and Kristinsson, H. G. 2008. Antioxidant activity of alkali-treated tilapia protein hydrolysates: A comparative study of five enzymes. J. Agric. Food Chem. 56 (4), 1434-1441. (25%)
- Davenport, M.D. and Kristinsson, H.G. 2008. Channel catfish (Ictalurus punctatus) muscle protein isolate performance processed under differing acid-aided and alkali-aided pH values. J. Food Sci. In Review.
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