Investigation of functional additives in chitosan-based edible coatings and their impact on physicochemical, bioactive, and microbial stability of orange-fleshed sweet potatoes (OFSP) during storage

Abstract

• Edible coatings were applied during storage of orange fleshed sweet potato (OFSP). • Coatings were developed from chitosan incorporating functional antioxidants. • Lemon grass essential oil (LEO) coated OFSP retained more carotene than uncoated. • Chitosan-LEO based coatings containing acidulants were most potent antimicrobials. • Chitosan-LEO based coatings alone enhanced the antioxidant capacity of OFSP. The efficacy of chitosan-based edible coatings (EC) in enhancing postharvest quality and extending the shelf life of orange-fleshed sweet potatoes (OFSP) is thoroughly investigated in this study. Six EC treatments (T2-T7) containing either chitosan alone/lemongrass essential oil (LEO), and/or citric/ ascorbic acids were applied to OFSP and stored under controlled atmospheric conditions (20 °C, 75 ± 5 % RH) for 28-day period along with an uncoated sample (T1). The samples were analysed weekly for the changes in physicochemical properties (weight loss, colour and texture), total phenolic content (Folin assay), antioxidant capacity (TEAC), bioactive components (HPLC) and microbial load. The results showed that T5 (chitosan/LEOs) and T7 (chitosan/LEOs/ascorbic/citric acid) coatings were particularly effective. T5 exhibited the least weight loss (5.65 %), while T1 (uncoated samples) recorded the greatest weight loss (13.23 %) by day 28. The main phenolic compounds identified in OFSP samples were 4-Caffeoylquinic Acid (4-CQA) and 3,5-Caffeoylquinic Acid (3,5-diCQA). At the end of the storage period, T5 displayed the highest TPC of 3.33 mg GAE g -1 , while T7 recorded the highest β-carotene content (0.72 ± 0.09 mg g⁻¹) and were significantly different from uncoated samples ( p < 0.05), suggesting the role of chitosan/ antioxidants in the stability of bioactive compounds. ECs especially T5 and T7 displayed strong antimicrobial properties, which were demonstrated by their significant reduction of mesophilic bacterial counts compared to the control ( p < 0.05). This work establishes a basis for developing bioactive coatings for preserving the quality and safety of OFSP, contributing to improved food security and nutritional outcomes.