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A preliminary exploration on the browning inhibition mechanism of disodium stannous citrate (DSC) in canned agaricus bisporus was studied. The inhibition is characterized by the inhibitory effect of both polyphenol oxidase (PPO) and residual oxygen. The absorption peak of enzymatic browning products of PPO and catechol with DSC was significantly weakened at 410 nm in UV-visible spectral wavelength scanning, which indicates that DSC can effectively inhibit the enzymatic browning reactions to reduce the formation of precipitation recognized as the browning products. In the other hand, the PPO activity remains 25.30% residual after reduced by DSC. But the two identical non-reductive electrophoretic band illustrate that DSC can't cut off the disulfide linkages that connect PPO enzyme protein peptide chain, which may result in negative effects on the higherorder structure of the protein and great decrease of PPO activity. Reduced by DSC, α-helix in the secondary structure of PPO decreased as opposed to the increase of β-sheet, β-turn and P2 conformation. The result of circular dichroism shows that DSC may reduce PPO activity by changing its molecular conformation. What's the most important is that the electrochemical theory inferred that in the acidic canned agaricus bisporus system, Sn2+ of DSC, acting as a stronger reducing agent, is about to spontaneously go through a reversible redox reaction with the residual oxygen in the bottle as a stronger oxidant and transformed to a weaker oxidant Sn4+ as well as a weaker reducing agent H2O in the end. |
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Keywords:PPO; DSC; browning; anti-browning agent; inhibition mechanism |
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