Development of Optimized Bioactive Nanocomposite Films Using a Central Composite Design for Control of Microbial Contamination in Stored Rice

Poly(butylene adipate-co-terephthalate) (PBAT) and polylactic acid (PLA)-based nanocomposite films were developed as active packaging materials for stored rice. The composition and synergistic effect of the active formulations (AF-1 and AF-2), cellulose nanocrystals (CNC), and glycerol (Gly) as independent variables were tested to reach the optimal antimicrobial nanocomposite films using response surface methodology (RSM) employing a central composite design (CCD). The inhibitory capacity (IC, %) of the developed films as a dependent variable against two bacterial and three fungal strains was measured using the agar volatilization assay. The ANOVA results showed a perfect fit of the regression models for the response, with significant P values (P ≤ 0.05) and high coefficient of determination (R²) values. Incorporating the CNC, Gly, and AFs significantly improved the PBAT films' elasticity, water barrier properties, and oxygen transmission rate (OTR) compared to the control films; however, the water and oxygen barrier properties of PLA films were compromised. The release data of AFs from the films was fitted with the Korsmeyer-Peppas model, indicating a Fickian or quasi-Fickian diffusion mechanism (n < 0.45). For the in situ study, the optimized bioactive PBAT-based films with 750 Gy of γ-irradiation synergistically reduced the bacterial and fungal load by 73-93% in stored rice after 2 months compared to the control treatments. The data confirms the potential applicability of the optimized films as promising candidates for active packaging for cereal grains and their ability to compete with traditionally used inert non-biodegradable plastic films.