Glucosinolates breakdown and enhanced nitrile formation in gamma irradiated minimally processed cauliflower (Brassica oleracia)

Glucosinolates (GSLs) and its degradation products from Brassica vegetables are of special importance due to diverse biological activities including health benefits. Gamma irradiation (a non-thermal post-harvest processing method) is known to extend shelf life of minimally processed cauliflower. However, the effect of gamma radi-ation on GSLs content and their hydrolytic products such as nitriles is less understood. In the current study, the mechanism of enhanced breakdown of major GSLs (sinigrin, glucoiberin and glucobrassicin) and formation of nitriles due to gamma irradiation was elucidated. The nitrile formation due to radiation stress was shown to be mediated by improved Fe2+ availability. The significant enhancement of nitrile formation was observed during Fe2+ supplementation studies. Gamma irradiation resulted in increase in total phenolic contents (35%), free radical scavenging activity (44%), and ferric reducing antioxidant power (FRAP) by 30%. The higher Fe2+ content was also observed in irradiated cauliflower and was maintained due to higher antioxidants (total phenolic contents) content. The change in expression of genes associated with GSLs biosynthesis was found to be not significant. Our study has illustrated the genetic and biochemical basis of GSLs reduction under radiation stress with special emphasis on role of Fe2+ in GSL metabolism after gamma irradiation.

Automated summary

Gamma irradiation enhances the breakdown of glucosinolates and the formation of nitriles in Brassica vegetables, which is mediated by improved Fe2+ availability. Gamma irradiation also increases total phenolic contents, free radical scavenging activity, and ferric reducing antioxidant power in cauliflower. However, there are no significant changes in the expression of genes associated with glucosinolate biosynthesis.