Mechanism of the inhibition of elevated CO₂ atmosphere on enzymatic browning of fresh-cut lotus roots

Abstract

Enzymatic browning is one of the main factors affecting the quality and shelf life of fresh-cut lotus root. The present study aimed to investigate the mechanism of inhibition of elevated carbon dioxide (CO2) on enzymatic browning by applying 20% CO2 to fresh-cut lotus roots. The results showed that 20% CO2 treatment significantly inhibited the increase of yellow-blue (b*) value, browning index, and the decrease of lightness (L*) value, thus delaying browning of fresh-cut lotus root. During the storage, the lotus root in 20% CO2 treatment group showed lower malondialdehyde (MDA) content and relative electrolyte leakage compared with those of the control group, indicating that 20% CO2 treatment effectively maintained membrane integrity and good locular distribution of enzymes and substrates. Enzymatic activity analysis showed that 20% CO2 treatment decreased the activities of phenylalnine ammonialyase, polyphenol oxidase and peroxidase, resulting in inhibiting the rate of enzymatic reactions. In addition, 20% CO2 treatment also decreased nicotinamide adenine dinucleotide reduced form (NADH) content and increased nicotinamide adenine dinucleotide phosphate reduced form (NADPH) content by activating nicotinamide adenine dinucleotide kinase (NADK) activity, which led to the decrease of energy charge and the enhancement of antioxidant levels, and caused delay in senescence and enzymatic browning during the storage. The above results suggest that elevated CO2 might be an effective strategy to inhibit postharvest enzymatic browning.

Keywords

• fresh-cut lotus root
• elevated CO₂ atmosphere
• enzymatic browning
• energy metabolism