PERTANIKA JOURNAL OF TROPICAL AGRICULTURAL SCIENCE

Postharvest deterioration and fungal infection significantly limit the shelf life of wax apples (Syzygium samarangense), while roselle decoction residues remain underutilised despite retaining bioactive compounds after processing. This study aimed to evaluate the efficacy of roselle decoction residues as functional ingredients in edible coatings for wax apple preservation. Fresh roselle calyx (RC) (F3), fresh decocted cordial residue (DCR) (F4), freeze-dried RC (F5), and freeze-dried DCR (F6) were incorporated into various coating formulations and applied to fruits stored for 15 days at ambient temperature. Roselle-based coatings significantly delayed fruit deterioration by preserving colour, firmness, and biochemical attributes (soluble solids, acidity, vitamin C, phenolics, and flavonoids) compared to controls. Water loss was reduced, and antioxidant capacity (DPPH) was better maintained in coated fruits. Among treatments, fresh RC (F3) exhibited the most consistent performance in preserving quality attributes, followed by F6, F4, and F5. Under wound-inoculation conditions, selected roselle-based coatings also delayed visible disease development caused by Pestalotiopsis sp. Overall, the findings demonstrate that roselle decoction residues can be valorised as natural antioxidant-rich coating agents, contributing to improved postharvest quality and supporting sustainable by-product utilisation.