Effect of Ultrasound-Assisted Oxalic Acid Treatment on Color Protection in Fresh-cut Apple during Storage
The study investigated the effect of ultrasound-assisted oxalic acid treatment on the color preserva-tion and freshness of fresh-cut apples during storage.Fresh-cut apples were placed in a 0.5%oxalic acid solu-tion and treated with ultrasound(300 W,40 kHz)for 3 min.The changes in browning index(BI),apparent color,peroxidase(POD)activity,polyphenol oxidase(PPO)activity,phenylalanine ammonialyase(PAL)activity,antioxidant capacity and total phenol content were investigated to systematically evaluate the color preservation and freshness effect of the ultrasound-assisted oxalic acid treatment on fresh-cut apples.The re-sults showed that compared to the control group,the BI value,PPO and POD activity of the fresh-cut apples in the experimental group were significantly reduced during the storage period(0-8 d),while the total phenolic content significantly increased at 2-8 d of storage(P<0.05).The PAL activity of the experimental group was significantly lower than that of the control group on days 2 and 8 of storage(P<0.05).Except for day 4 of stor-age,the antioxidant capacity of fresh-cut apples in the experimental group was significantly higher than that in the control group(P<0.05).Therefore,ultrasound-assisted oxalic acid treatment can delay enzymatic brown-ing by inhibiting the activities of PPO,POD,and PAL,and by enhancing the antioxidant capacity of fresh-cut apples,thereby achieving the goal of color preservation and freshness.