Effect of Pretreatment Methods on Cellulose Extraction From Corncobs and Its Application as a Fruit Coating

This study examined pretreatment strategies to enrich cellulose from corncob biomass and evaluated the resulting cellulose as a natural fruit coating. Corncobs were pretreated by (i) steam at 100 or 120°C for 2 h or (ii) steam–NaOH using 2, 6, or 10 M NaOH at 80, 100, or 120°C for 2 h. The optimum condition (10 M NaOH, 120°C) produced 51.93±0.12% cellulose (30.90% higher than untreated), with hemicellulose at 25.45±0.18% and lignin 16.56±0.43%. Delignification with 1.3 M NaClO₂ at 75°C increased cellulose purity to 55.93±0.23%; however, additional delignification cycles did not significantly change cellulose content (p>0.05). The purified cellulose was slightly less bright than commercial carboxymethyl cellulose (CMC). In application, a 3% (w/v) aqueous extracted-cellulose coating was applied to Nam Dok Mai mangoes of similar maturity and compared with CMC-coated mangoes and an uncoated control. After 7 days, weight loss was 9.09% for cellulose-coated fruit and 8.73% for CMC-coated fruit, versus 13.60% for uncoated fruit. Moreover, both coatings delayed visible decay (no visible spoilage up to day 7; control showed spoilage by day 4). These results indicate that corncob-derived cellulose is a promising biodegradable coating for fruit preservation.