Chia seed mucilage film with Lactobacillus acidophilus LA-5 postbiotics: Preparation and antimicrobial performance in ultra-filter cheese against Escherichia coli O157:H7

Abstract

A novel biopolymer-based film with antibacterial properties was developed using chia seed mucilage (CSM) and postbiotics. Postbiotics were prepared from Lactobacillus acidophilus LA-5 using Ultra-filter (UF) cheese whey as the culture medium, as a sustainable approach. CSM -LA-5 films containing LA-5 postbiotics (200 mg/mL) and CSM were prepared using a casting method. The CSM film exhibited a weak inhibitory effect against Escherichia coli O157:H7 (12.2 ± 0.2 mm). However, incorporating LA-5 into the CSM film significantly enhanced (P < 0.05) antimicrobial activity, resulting in a larger inhibition zone (15.3 ± 0.5 mm). The presence of active LA-5 postbiotic compounds in the CSM -LA-5 film was confirmed using FTIR spectroscopy. Field Emission Scanning electron microscopy images confirmed the even distribution of LA-5 on the CSM film. The embedding of postbiotics in the CSM film caused changes in CSM mechanical properties, which decreased tensile strength (from 0.98 MPa to 0.49 MPa) and increased strain-to-break (from 209 % to 276 %), mostly owing to the presence of high molecular weight compounds. The antimicrobial properties of the films were evaluated against E. coli in UF cheese. The initial bacterial count on the surface of UF white cheese (∼ 4.46 log₁₀ CFU/g) was completely inactivated by CSM -LA5 (200 mg/mL) after 15 days of storage at 4 °C. In contrast, reductions in E. coli of about 2.46 and 1.81 log10 CFU/g were observed after 15 days in the CSM film and control group, respectively. Biopolymer-based films incorporating LA-5 postbiotics exhibit innovative antibacterial properties and are thus suitable for use in cheese packaging.

Keywords: Active packaging; Cell-free supernatant; Edible films; Mucilage; Whey.