Vegetable tannin from Xylocarpus granatum fruit seeds: extraction, characterization, and application in leather manufacturing

Leather processing involves a significant operation called retanning, which develops the physical properties of the final leather. It can ensure eco-friendly and sustainable leather production through the utilization of various vegetable tannin reagents, resulting in a reduced impact on hazardous elements, such as chromium. This study focuses on the extraction of tannin from Xylocarpus granatum seed for the potential use in retanning. The presence of tannin in Xylocarpus granatum seed showed about 16.77 % with 3110 mg/L TDS, 10.25 % moisture, and 5.4 pH. The tannin extracted from Xylocarpus granatum seed was characterized through FTIR analysis to identify the presence of essential functional groups in tannin. The Xylocarpus granatum retanned leather revealed superior physico-mechanical properties such as tensile strength (292.89 kg/cm 2 in parallel and 285.65 kg/cm 2 in perpendicular), elongation at break (51.18 % in parallel and 49.8 % in perpendicular), ball burst strength (30.59 kg), distention (7.19 mm), and shrinkage temperature (109.2 °C). Additionally, the crust leather assessment through SEM analysis revealed a compact, well-organized fiber orientation. Hence, these observations suggested that the use of Xylocarpus granatum tannin in leather processing could be a natural, sustainable, and environmentally friendly alternative. • Ecofriendly natural tannin extracted from native X. granatum fruit seeds for leather tanning. • Tannin extracted in aqueous phase from ground X. granatum fruit seeds was 16.77 %. • Leather tanned with extracted tannin showed required physical properties at standard level. • SEM micrographs depict a similar fiber orientation compared to the conventional leather.