Anatomia, histologia e fitoquímica no escurecimento enzimático do inhame minimamente processado

Abstract

Minimally processed yams cause several types of cellular damage, which can produce oxidative stress and trigger enzymatic browning of tissues, thus compromising the final quality of the product. The aim of this study was to characterize and evaluate anatomically the oxidative processes in the peripheral, intermediate and central regions of minimally processed yam slices. The tubers were minimally processed in slice format, kept in polystyrene trays and stored at 5±2 oC for 15 days, with evaluations occurring every three days with four repetitions. The anatomical characterization was conducted and the physicochemical and biochemical characteristics were analyzed, such as total phenols, peroxidase activity (POD), polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL) in the peripheral, intermediate and central regions. Different structures were identified in the various regions of the yam slice, such as starch, vascular cambium, raphide crystals, parenchyma with and without starch, tannins and vascular bundles, which are irregularly distributed. The pH, acidity, brix and firmness remained stable throughout the refrigerated storage and there was no significant difference in these parameters in the analyzed regions. PAL activity and phenol content in the tissues remained stable, while PPO activity decreased with storage time. Darkening was also observed in all areas of the slice during the storage period. Thus, it was found that refrigerated storage positively regulated the metabolism in yam tissue, attenuating the physiological effects induced by cutting. The induction of browning is due to the distribution of vascular bundles and the enzyme PPO throughout the plant tissue of the minimally processed yam slices.