Preparation of gelatin/carboxymethyl cellulose/guar gum edible films enriched with methanolic extracts from shallot wastes and its application in the microbiological control of raw beef

In this study, agricultural wastes from red onions or shallots were utilized to incorporate into edible film formulation from gelatin/carboxymethyl cellulose/guar gum for the preservation of fresh beef tenderloin. Shallot tunic extract (STE) was rich in phenolics (2613.54 ± 28.96 mg gallic acid equivalent/L) and anthocyanins (69.72 ± 0.72 mg cyanidin-3-glucoside/L) with high antioxidant and antimicrobial activities against eleven pathogenic microorganisms (Gram-positive bacteria, Gram-negative bacteria and fungi), especially Citrobacter freundii, Proteus mirabilis, and Listeria monocytogenes. According to the physical characterization (SEM, XRD, FT-IR), the addition of STE into film formulation led to a more identical microstructure, lower intensity peak at 2θ of 20°, and increase in the vibration of NCO group. Regarding the microbiological quality, total plate counts of beef coated with STE-containing edible films were controlled equivalent to the uncoated beef during storage. It is noticeable that E. coli, Coliforms and Staphylococcus aureus were effectively inhibited up to seven days by coating with STE-containing films, as illustrated by their significant lower counts compared to control samples. The lipid oxidation products were maintained at levels similar to those found in the original beef (0.17–0.27 mg malondialdehyde/kg of meat) owing to the STE-enriched films' ability to inhibit lipid oxidation.