100-1 |
Gelation characteristics of alkaline and acid solubilization of fish muscle proteins |
J. YONGSAWATDIGUL, School of Food Technology, Suranaree University of Technology, Nakhon Ratchasima, 30000, Thailand and J. W. Park, OSU Seafood Lab & Dept of Food Sci and Tech, Oregon State University, 2001 Marine Drive #253, Astoria, OR 97103. Muscle proteins exhibit high solubility at acidic and alkaline pH. Gels of recovered proteins by acid solubilization (pH 2.5) followed by subsequent precipitation at their isoelectric point have displayed high elasticity. However, gelation mechanisms and rheological properties of acid-treated or alkaline-treated muscle proteins are not fully understood. The objective of this study was to investigate thermal denaturation and textural properties of fish proteins solubilized at acid and alkaline conditions. Rock fish (Sebastes spp.) was used as a model for this study. Solubility of whole muscle and actomyosin was determined at pH ranging from 2-12. Acid and alkaline-treated muscle proteins were prepared by homogenizing minced fish in 9 volumes of distilled water and adjusting the pH to acidic (2.5) and alkaline (11) conditons to obtain the maximum solubility. Recovery of proteins was achieved by adjusting pH to isolectric point (5.0). Precipitates were centrifuged to remove water and their pH was adjusted to 7.0. Gels of recovered protein were prepared at 2% NaCl and 80% moisture content. Total sulfhydryl groups during gelation were determined using DTNB. Denaturation patterns and dynamic rheology were measured using DSC and Bohlin rheometer, respectively. Texture and color of samples were assessed using 5 mm spherical probe and Minolta colorimeter, respectively. Muscle proteins of rock fish showed the highest solubility at pH 2-2.5 and 12, and the lowest solubility at 5-6. Alkaline and acid solubilization resulted in protein denaturation according to DSC thermogram and low solubility in 0.6 M KCl solution. Alkaline and acid-treated proteins readily aggregated upon heating. Disulfide linkages appeared to be predominant in alkaline-treated gel, corresponding to the highest punch force. Higher b* value was observed in both acid and alkaline-treated gels. Acid and alkaline solubilization could give higher yield in surimi processing. Alkaline-aided method appeared to enhance gel strength.
Session 100, Seafood Technology: Texture, Chemistry
|