Effects of Hot Water Combined with UV-C Treatment on Chinese kale (Brassica oleracea var. Alboglabra) during Storage

Abstract

Yellowing and wilting are the major postharvest losses of Chinese kale (Brassica oleracea
var. Alboglabra) during storage. This research aimed to investigate the effects of pre-treatments including i) hot water (HW) dipping at 45°C for 30s, ii) ultraviolet C irradiation (UV-C) at dose of 1.82 kJ m-2 and iii) a combined treatment between HW and UV-C (HW+UV-C) on the quality of Chinese kale compared with the control treatment during cold storage. After that,
all the samples were packed in perforated polyethylene bags before putting into storage at
10°C, 80-85% RH for 7 days. The results showed that leaves of the Chinese kale in the control
group become yellowing faster than other treatments. The control samples had a higher trend
in L*, b* values and Chroma compared with other treatments during storage periods of 7 days.
The control samples had the lowest hue angle (h° = 95.7) after 7 days of storage. However,
there was no significant difference in the changes of h° in all treatments during storage
periods. The samples pre-treated with HW+UV-C had the highest percentage of weight loss
(8.1 and 10.8%) while the control treatment or the samples treated with HW or UV-C alone
had significant (p < 0.05) less weight loss which was in the ranges between 2.3-3.5% and
3.0-5.1% after 5 and 7 days of storage, respectively. There was no significant difference in the
changes in chlorophyll content for all treatments during storage. In conclusion, the UV-C
treatment significantly (p < 0.05) delayed yellowness (especially, b* value), had less weight
loss compared with other treatments. The quality of Chinese kale was maintained by the UV-C
treatment during storage periods of 4-5 days.