Kinetics of heat denaturation of proteins extracted from Pinctada martensii meat

South China Sea pearls are well known worldwide, and the pearl oyster Pinctada martensii is cultured for pearl production in China. Following the development of the pearl industry, Pinctada martensii is now cultured at very large scale specifically for pearl production, with the oyster meat left aside as a typically unused byproduct of the pearl industry. However, Pearl oyster meat is a good source of shellfish protein (74.9% protein/dry basis) at a low cost.Recently, the influence of food protein processing, storage and heat treatment is an area of growing interest. In particular, some thermal processing has a significant impact on animal muscle protein structure, enzymatic properties etc. Proteins are the most important ingredients in the food. They are not only important in nutrition, but also affect the texture and flavor of the food. Muscle proteins are generally classified into sarcoplasmic proteins, myofibrillar proteins (myosin, actin and actomyosin) and connective tissue or stromal proteins (collagen).This paper studied the kinetics of thermal denaturation of proteins (water-soluble and salt-soluble protein ) extracted from Pinctada martensii meat in order to understand the thermal denaturation discipline of aquatic protein and make better use of their functional properties. Due to differences in the structure and composition, the two protein fractions denaturation was best described by assuming an apparent reaction order of 1.1 and 1.3, respectively. D values, the time required to reduce the protein by 90%, were 33 333、12 500、3 333、1 667 and 769 s for the water-soluble protein fraction and 50 000、12 500、5 000、2 000 and 1250s for the salt-soluble protein fraction at 60, 70, 80, 90, 100℃ respectively. There was significant difference of the two proteins for D value except at 70℃. This may be due to an easier to form gel for the salt-soluble protein under the condition of 65-70℃. The results showed that the thermal denaturation rate of two proteins continued to accelerate in the range of heating temperatures and the salt-soluble protein fraction was more heat-resistant than the water-soluble protein fraction. Protein denaturing reaction is very complicated, and many reactions occur as the temperature changes. The different heat treatment conditions have different effects on the expansion of the peptide chain and protein aggregation in the process of protein denaturation. Similarly, Z values, the degrees necessary to reduce the D value in one logarithmic cycle, were estimated to be 24.1℃ for water-soluble protein fraction and 25.0℃ for the salt-soluble protein fraction. The denature reactions’ activation energy of the water-soluble protein fraction and salt-soluble protein fraction were 101.83 and 112.78 kJ/mol respectively. The entropy value of protein thermal denaturation is a smaller process, and our results are consistent with it. The entropy change of the system is negative. Therefore, these results will provide the theoretical basis for the data for Pinctada martensii meat protein high value utilization. In addition, it is of great practical significance for further development of new high-quality food use of their functional properties.