Inhibition of Polyphenol Oxidases and Peroxidase Activities in Green Table Olives by some Anti-browning Agents

Mohsenabadi Maryam, Ghasemnezhad Mahmood, Hashempour Abuzar, Hasan Reza, Sajedi
2017 Agriculturae Conspectus Scientifi cus   unpublished
Almost, all table olive cultivars are susceptible to the formation of brown spots due to mechanical damage during harvesting and processing. Th erefore, application of some anti-browning agents might be an eff ective strategy to minimize unfavourable eff ects of enzymatic browning in green table olives. Th e aim of this study was to assess the eff ect of ascorbic acid (AA), citric acid (CA), oxalic acid (OA), 4-hexylresorcinol (HR) and sodium hexametaphosphate (NaHMP) on reducing enzymatic
more » ... ing of four green table olive cultivars ('Mari', 'Shengeh', 'Manzanilla' and 'Zard') fruit. Th e results showed that 'Mari' and 'Shengeh' potentially had the highest browning index. AA could reduce peroxidase (POD) activity just in 'Mari', but NaHMP could benefi cially suppress its activity in both cvs. 'Manzanilla' and 'Mari'. In general, the monophenolase activity of polyphenol oxidase (PPO) was signifi cantly higher than its diphenolase activity in all studied cultivars. Th e highest inhibitory eff ect on monophenolase activity was found in 'Manzanilla' fruit by CA and OA, while HR and NaHMP could suppress monophenolase activity of 'Mari' fruits. Diphenolase activity of PPO with pyrocatechol and dopamine HCl substrates was also dependent on olive cultivars. Th e minimum diphenolase activity of PPO for both substrates was found in 'Zard' fruit with the lowest browning index. Th e inhibitory eff ect of anti-browning agents on reducing diphenolase activity of PPO with dopamine hydrocholoride (DPOA) substrates was cultivar-dependend. Total phenolic content of treated fruits was higher than control. Overall, this result confi rms that the potency of anti-browning agents on suppressing POD and PPOs enzymes that are involved in fruits browning was completely cultivar-dependend.