Physico-Mechanical and Antimicrobial Properties of Isolated Soy Protein Film Incorporated with Peppermint Essential Oil on Raw Hamburger

Meat products are highly perishable and require protection to maintain their quality. Bioedible films incorporated with essential oils have recently received attention due to their benefits as AntiMicrobial (AM) active packaging. The aim of this study was to evaluate the physico-mechanical properties and antimicrobial activity of Isolated Soy Protein (ISP) film containing Peppermint Essential Oil (PEO) on shelf life and sensory quality of raw hamburger. The ISP film incorporated with PEO at 1, 2, and 3% (v/v) were prepared by solvent casting method. The results showed that the incorporation of PEO caused a significant decrease and an increase (P< 0.05) in tensile strength and elongation-at-break, respectively. Increment of thickness, Water Vapor Permeability (WVP), and decline in moisture content was recorded as the amount of oil increased (P< 0.05). In addition, Lightness/darkness (L*), Whiteness Index (WI), and redness/greenness (a*), and yellowness/blueness (b*) increased, while the total color difference (ΔE) decreased by adding PEO. PEO-incorporated film (at 3% v/v) exhibited higher inhibitory activity against Staphylococcus aureus, Escherichia coli, and lower for Salmonella enterica using disc diffusion method. Microbial analysis and pH measurement of raw hamburger covered with ISP-PEO film showed no inhibitory effect against test bacteria when applied on raw hamburger, whereas the inhibited total bacterial growth exceeded the acceptable limit until the end of refrigerated storage. This film was able to prolong the shelf life of hamburger for up to 7 days. Therefore, this new antibacterial film has considerable potential to be used as meat packaging material.