Application of Coating Chitosan Derivatives (N,O–Carboxymethyl Chitosan/Chitosan Oligomer Saccharide) in Combination with Polyvinyl Alcohol Solutions to Preserve Fresh Ngoc Linh Ginseng Quality

Abstract

The postharvest preservation of Ngoc Linh ginseng (NL ginseng) is essential to retain its quality and sensory values for prolonged storage. In this study, the efficacy of NL ginseng preservation by coating chitosan derivatives in combination with polyvinyl alcohol (PVA) solutions was investigated under refrigeration conditions (~3 °C; ~40% RH) for 56 days. The effect of the chitosan–based solutions, including N,O–carboxymethyl chitosan (NOCC), chitosan oligomer saccharide (COS), or chitosan (CS), and the blend solutions (NOCC–PVA or COS–PVA) on the coated NL ginsengs was observed during storage. The pH values, viscosity, and film-forming capability of the coating solutions were determined, while the visual appearance, morphology, and mechanical properties of the films formed on glass substrates as a ginseng model for coating were also observed. The appearance, skin lightness, weight loss, sensory evaluation, total saponin content (TSC), total polyphenol content (TPC), and total antioxidant capacity (TAC) of the coated NL ginsengs were evaluated. The findings showed that the observed values of the coated NL ginsengs were better than those of the non-coated samples, with the exception of the COS–coated samples, which had completely negative results. Furthermore, the NOCC–PVA solution exhibited a better preservation effect compared with the COS–PVA one based on the observed indices, except for TPC and TAC, which were not impacted by the coating. Notably, the optimal preservation time was determined to be 35 days. This study presents promising preservation technology using the coating solution of NOCC–PVA, harnessing the synergistic effect of pH 7.4 and the form–firming capacity, to maintain the shelf life, medicinal content, and sensory attributes of NL ginseng.