Effects of cotton leaf extract bioactive compounds in the PVA (polyvinyl alcohol) packaging films on white bread storage shelf life

Abstract

This study developed polyvinyl alcohol (PVA)-based active films with cotton leaf extract (CLE) to extend bread’s shelf-life. Bread slices were wrapped with commercial low-density polyethylene (LDPE, control) or PVA films containing 0, 1, 2, and 4 mL CLE and stored at 30 °C for 15 days. The water vapor transmission rate of the PVA films ranged from 51.29 ± 1.53 to 54.30 ± 0.65 g/m²·h, while CLE incorporation reduced water solubility from 20.65 ± 1.39% to 5.80 ± 1.60%. Compared with LDPE, the PVA films showed higher elongation but lower tensile strength and Young’s modulus. Bread pH, firmness, and color (a* and b*) increased over time, while total titratable acidity (TTA), moisture, water activity (a_w), and whiteness (L*) decreased. The T₂ (2 mL CLE) maintained superior texture (29.43 ± 0.35 N), moisture (12.71 ± 0.06%), and a_w (0.707 ± 0.006) by day 15. The T₃ (4 mL CLE) showed the highest pH (6.14 ± 0.01) and TTA (0.706 ± 0.003%), retaining strong antioxidant activity, with DPPH (1, 1-diphenyl-2-picrylhydrazyl) free radical scavenging and total phenolic content (TPC) declining from 134.32 ± 0.60 to 84.60 ± 0.03 µg AAE/g and 4.55 ± 0.015 to 2.62 ± 0.015 mg GAE/g. Microbial analysis confirmed T₃ as most effective, keeping bacteria, mold, and yeast below safety limits, while control exceeded limits by day 6. Sensory evaluation favored T₂ for taste, aroma, and overall acceptability. The CLE-enriched PVA films, notably T₃, extended bread shelf life, whereas T₂ balanced preservation and consumer preference as a sustainable packaging alternative.