Postharvest browning in Yam ( Dioscorea spp.): Mechanisms, scenario-specific control strategies, and practical applications

Browning is a major postharvest and processing-related quality problem in yam ( Dioscorea spp.), but its occurrence and control depend strongly on product form. This review summarizes yam browning from a product-specific, mechanism-based, and application-oriented perspective, covering whole yam tubers, fresh-cut slices, yam purée/paste, and thermally processed products. Whole tubers are mainly affected by storage conditions, wound responses, and oxygen exposure, while fresh-cut slices rapidly develop polyphenol oxidase (PPO)/peroxidase (POD)-mediated enzymatic browning after tissue disruption. Yam purée and paste may involve enzymatic oxidation, oxygen diffusion, and pigment-related color changes, whereas dried or heated products are more associated with Maillard reaction, thermal darkening, and moisture-dependent non-enzymatic browning. Bisdemethoxycurcumin (BDMC)-related yellowing is also highlighted as a distinctive color-change pathway in yam. Based on these mechanisms, key control targets include oxygen restriction, enzyme activity reduction, quinone reduction, BDMC/yellowing regulation, and moisture–thermal management. Representative strategies, including organic acid or antioxidant dips, edible coatings with modified atmosphere packaging, optimized storage, drying/heating control, spectroscopic monitoring, and intelligent cold-chain management, are critically compared in terms of advantages, limitations, cost-effectiveness, scalability, and effects on nutritional and functional quality.