Two soy protein 11S fractions with different surface sulfhydryl contents were prepared. Utilizing analytical ultracentrifugation, the effects of storage time and hydrogen peroxide at different concentrations (0.5—100 mmol/L) on the two 11S fractions were investigated. Results show that after removing 2-mercaptoethanol (2-ME) by size exclusion chromatography, the 11S fraction with high surface sulfhydryl content (2.0 mol sulfhydryl/mol 11S) progressively formed 15S and 21S in dilute solutions during storage at 4 °C for 82 days. While, the 11S fraction with low surface sulfhydryl content (0.2 mol sulfhydryl/mol 11S) was stable under the same condition. Moreover, after treating the 11S with high surface sulfhydryl content with 1 mmol/L H 2 O 2 , the weight percentage of 15S reached the maximum value of 20%. The 15S induced by air and H 2 O 2 could be totally converted to 11S with the addition of 10 mmol/L 2-ME, which could be attributed to that the disulfide bond linking two 11S molecules is on the surface of the 15S and easily accessible to the reducing agent 2-ME. This study helps us to deeply understand the formation mechanism of 15S and the stability of 11S.
Yifan Zhu,Mubango Elliot,Yanhong Zheng,Jing Chen,Dongzhi Chen,Shanggui Deng
Atmospheric cold plasma (ACP) is a novel nonthermal technology with potential applications in maintaining and improving food quality. The effect of ACP on the activity and structure of mushroom ( Agaricus bisporus ) polyphenol oxidase (PPO) was evaluated. Results demonstrated that the dielectric barrier discharge (DBD) based plasma technology could inactivate PPO (up to 69%) at 50 kV with the increased concentrations of H 2 O 2 and NO x . An obvious enhancement of surface hydrophobicity was observed, whereas a gradual reduction of total sulfhydryl content was recorded with the increasing exposure time. Data from circular dichroism, atomic force microscopy, particle size distribution and fluorescence spectra displayed the rearrangement of secondary structure and disruption of the tertiary structure. Red shifts of fluorescence spectra showed positive correlations with the inactivation rate of PPO. Therefore, ACP treatment could be served as an alternative approach to inactivate undesirable enzymes to minimize the loss of food nutrition and quality.
危险品化学品经营许可证（带存储）