Effect of color protection treatment on the browning and enzyme activity of Lentinus edodes during processing

Fresh Lentinus edodes (L. edodes) are prone to browning (including enzymatic and nonenzymatic browning), which affects their quality and leads to economic losses during later processing. This study explored various effective color protection methods (color protection reagent and/or blanching) for inhibiting the browning of L. edodes. First, a single-factor experiment and a response surface method were used to optimize the concentration of the color retention reagent. The compound color retention reagent (comprising 0.1% phytic acid, 0.8% sodium citrate, and 0.5% d-sodium erythorbate) had the smallest total color difference (ΔE) value, suggesting that the compound color reagent had a better inhibiting effect than the single agent. Following this, the blanching conditions were studied; the polyphenol oxidase (PPO) activity was the lowest when the blanching temperature was 90°C and blanching time 180 s, indicating that browning is likely to be minimal. Finally, comparing the oxidase activity and total color difference (ΔE) revealed that combining the two color protection methods inhibits browning better than using a single method (color protection reagent or blanching). In addition, the polysaccharide and vitamin C (VC) contents of L. edodes under optimal color protection conditions were determined, which were 0.96 and 2.54 g/100 g fresh weight (FW), respectively. The results demonstrated that this color protection method effectively inhibits browning, reduces the nutritional loss, and improves the quality of L. edodes.