Evolution of antioxidant enzymes activity and volatile release during storage of processed broccoli (Brassica oleracea L. italica)

The objective of this study was to investigate the effects of temperature treatments (i.e. freezing at −18 °C, cool storage at 4 °C and heating at 50, 70 and 100 °C for 10 min) on the activity of peroxidase (POD), lipoxygenase (LOX), ascorbic acid oxidase (AAO), superoxide dismutase (SOD) and catalase (CAT) in broccoli (Brassica oleracea L. italica). Volatiles released during storage at 20 °C for 24 h were monitored using on-line Proton Transfer Reaction Mass Spectrometry (m/z 21-180). Partial Least Square Regression (PLSR) was used to evaluate possible correlations between enzymes and volatiles released during storage. The results showed that temperature treatment had significant effect on all enzymes, except LOX. Temperature treatment at 70 °C resulted in at least 65% decrease in POD and AAO activity. In contrast, SOD and CAT activities generally increased during storage after temperature treatments. PLSR2 results showed that volatiles released after different temperature treatments and 24 h storage had a strong correlation with the residual activity of POD, AAO and SOD but not CAT and LOX. PLSR1 results suggested that POD had the highest correlation to volatile release during storage of processed broccoli followed by AAO, SOD, CAT and LOX (the least).