An Evaluation on Physical Characteristics of Konjac Polysaccharides-Based Film Coating and Its Application for Strawberries Preservation

Konjac is an ideal candidate for edible coatings on fruits due to its hydrophilic properties, film-forming ability, barrier properties, safety, and biodegradability. Meanwhile, the high market demand for strawberries necessitates post-harvest treatment to extend their shelf life and preserve their quality, as strawberries are known for their fragile skin and soft texture. To fully utilize konjac and develop high-quality coating films, native konjac flour (NKF) and konjac glucomannan (KGM) were extracted from its corm and used as a coating film for strawberries in the present study. Therefore, this study aimed to compare the physical properties of the film coatings between NKFandKGM,andevaluate their effects on strawberries preservation over 7 days of storage. A multistage extrac tion process was employed to isolate NKF and KGM, after which the glucomannan content was measured. NKF yield was 31.81%, exceeding KGM yield of 26.42%, and the glucomannan content obtained of NKF (25.93%) was higher than KGM (21.41%). Nuclear magnetic resonance spectroscopy confirmed that both NKF and KGM con tain glucomannan in their structure. Furthermore, both NKF and KGM were combined with carboxymethyl cel lulose (CMC) and glycerol to produce eight thin-layer films to assess their physical and mechanical properties. Compared to the KGM variant, the NKF variant generally exhibited higher moisture content, water vapor trans mission rate, and tensile strength. However, NKF was less effective than KGM in extending strawberry storage life, leading to faster color changes and greater weight loss, despite maintaining similar hardness values. Nonetheless, konjac-based coatings were generally effective at maintaining the freshness and quality of strawberries compared to uncoated samples. Konjac shows promise as an edible coating, improving fresh produce shelf life and appeal, aligning with consumer preferences for natural and sustainable products.