O escurecimento e a cicatrização em inhame (Dioscorea spp.) minimamente processado é modulado pela região do tubérculo, aplicação de ácido ascórbico e temperatura de conservação

Abstract

Mechanical damage caused by peeling and cutting affects the biochemical and physiological processes of yam, triggering enzymatic oxidation and inducing rapid defense responses, such as the formation of structural barriers at the wound site. This study aims to investigate, in an integrated manner, the physiological, biochemical, and structural responses of minimally processed yam (Dioscorea cayenensis), evaluating the effects of tuber region, storage temperature, and ascorbic acid application on enzymatic browning and wound healing. Slices from the apical (AP), medial (ME), and distal (DI) regions were subjected to minimal processing, treated or not with ascorbic acid (1% w/v), and stored at 5 °C (browning) and at 5 and 20 °C (lignification). Quality and physicochemical parameters, phenolic metabolism, enzymatic activities (PPO, SOD, CAT, POD, and PAL), and lignin deposition were evaluated. Visual quality progressively declined during storage, with more pronounced losses in the apical region. ascorbic acid delayed browning and extended the acceptability of the medial and distal regions. Browning dynamics were modulated by polyphenol oxidase (PPO) activity, superoxide dismutase (SOD), and phenolic content, indicating that when enzymatic protection becomes insufficient, phenolic compounds act as non-enzymatic antioxidants. Chromatographic analysis revealed selective accumulation of hydroxycinnamic acids and flavonoids, indicating activation of the phenylpropanoid pathway in response to post-processing stress. The wound healing process was strongly influenced by temperature. At 5 °C, an antioxidant response predominated, with no detectable lignin deposition. In contrast, at 20 °C, increased activities of phenylalanine ammonia-lyase (PAL) and peroxidase (POD) were observed, along with lignin deposition, characterizing a structural response. Overall, the results demonstrate that the quality of minimally processed yam is determined by the interaction between tuber region, storage temperature, and ascorbic acid application, highlighting the multifactorial nature of oxidative stress regulation in minimally processed yam.