Abstract:

This study aimed to explore the optimum initial gas composition for modified atmosphere packaging (MAP)
of sword bean. The effects of different initial gas composition (O2 + CO2, N2 as the balance gas) on storage quality and
antioxidant enzyme activities of sword bean during storage at (20 ± 1) ℃ and relative humidity (RH) of 80%–90% were
studied. Sword bean packaged in air were used as controls. The result indicated that packages with 1%–4% O2 + 1% CO2
showed the best sensory quality, and could significantly inhibit the decline in the contents of crude fiber and malonaldehyde
(MDA) when compared with other packages and controls. Furthermore, sword bean packaged in 1%–4% O2 + 1% CO2 could
maintain high contents of chlorophyll, vitamin C, soluble sugar and reducing sugar. Through analysis of antioxidant enzyme
activities of sword bean, we found that packages with 1%–4% O2 + 1% CO2 significantly delayed the increase in polyphenol
oxidase (PPO) activity and the decrease in superoxide dismutase (SOD) activity in comparison with other packages and
controls. However, the results showed that the effect of packages with 1%–4% O2 + 1% CO2 on soluble protein and peroxidase
(POD) activity of sword bean was not better than that of other packages, and no differences in weight loss ratio were found
among all packages. Then, the comprehensive evaluation by principal component analysis (PCA) based on the previous analysis
showed that packages with 1%–4% O2 + 1% CO2 were optimal for maintaining the quality of sword bean during storage.

Key words: sword bean, MAP, storage quality, antioxidant enzyme activities, principal component analysis