Thermal denaturation of threadfin bream muscle proteins as affected by some additives and quality changes
ผลของสารเจือปนและการเปลี่ยนแปลงคุณภาพต่อการสูญเสียสภาพธรรมชาติของโปรตีน
กล้ามเนื้อปลาทรายแดงโดยความร้อน
Soottawat Benjakul, Asst. Prof., D. of Food Tech., F. of Agro-Industry, PSU.
Wonnop Visessanguan, Researcher, National Center for Genetic Eng. and Biotech. (NSTDA), Bangkok
Prawes Kookkeaw, D. of Food Tech., F. of Agro-Industry, PSU.
Corresponding e-mail : bsoottaw@ratree.psu.ac.th
Published : Songklanakarin J Sci Technol 2000, 22(3) : 329-338
Key words : thermal denaturation, muscle proteins, additive, threadfin bream
Thermal denaturation of threadfin bream muscle protein was studied with differential scanning colorimetry (DSC) by monitoring Tmax of transition and denaturation enthalpy. Tmax of 49.8oC and
enthalpy of 0.34 J/g were observed for myosin, whereas actin underwent denaturation with Tmax of 73.2oC and enthalpy of 0.49 J/g. Additives directly affected the thermal transition of muscle proteins. The addition of 2.5%NaCl or 2.5%NaCl with 0.2%Na-tripolyphosphate resulted in a decrease in
Tmax of actin and a decrease in enthalpy of both actin and myosin. The effect of cryoprotectant on proteins was also investigated. Addition of 4% sucrose and 4% sorbitol led to a slight increase in Tmax of myosin. However, no transition of actin was observed in the presence of NaCl and cryoprotectants.
Chemical changes in threadfin bream mince were observed during iced storage for 8 days.
Total volatile base and trimethylamine increased slightly at the first 4 days of storage and sharply increased up to 8 days. Autolysis occurred throughout the iced storage, especially during 4-8 days. Tmax of myosin shifted to a lower temperature and a lower enthalpy was obtained when the storage time increased. This suggested that some additives and the protein degradation had an effect upon
the thermal denaturation of threadfin bream muscle proteins.
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