Sustainable Probiotic Whey Protein Edible Films for Soft Cheese Quality and Shelf-Life Enhancement

Soft spread cheese is highly perishable, and conventional packaging offers limited protection against surface spoilage. Here, we present a sustainable, multifunctional solution: edible films made from whey protein concentrate (WPC), a valuable by-product of the cheese industry, incorporated with the probiotic Lactobacillus acidophilus LA5 (LA5). The objective of this study was to evaluate these films as active coatings for soft cheese, specifically assessing their physicochemical properties, probiotic viability during storage and simulated gastric transit, and their impact on cheese microbial stability and sensory quality over 60 days. Applied as active coatings on soft cheese stored at 4 °C for 60 days, these films were evaluated for their physicochemical properties, probiotic viability, microbial stability, and sensory acceptance. The incorporation of LA5 did not significantly alter film thickness (control: 0.20 ± 0.03 mm; test: 0.18 ± 0.02 mm), moisture content (control: 33.42 ± 0.54%; test: 32.34 ± 1.28%), or water solubility (control: 21.44 ± 1.14%; test: 22.89 ± 0.75%) (p > 0.05). However, mechanical properties were markedly modified: tensile strength decreased from 35.42 ± 5.38 MPa (control) to 6.04 ± 0.55 MPa (test), while elongation at break increased from 4.87 ± 0.93% to 68.23 ± 3.46% (p < 0.05), indicating a transition from rigidity to flexibility upon probiotic incorporation. The probiotic strain exhibited exceptional resilience, retaining 100% viability during simulated gastric exposure at both day 0 and day 30 of storage. During cheese storage, LA5 counts in test film-coated samples remained above the recommended therapeutic threshold (10⁶ cfu/g), starting at 7.44 ± 0.15 log(cfu/g) on day 0 and maintaining 6.56 ± 0.20 log(cfu/g) after 60 days. Critically, yeast and mold spoilage were delayed in probiotic-coated cheese, with detectable growth appearing only at day 60 (1.64 ± 1.34 log(cfu/g)), whereas uncoated cheese showed spoilage as early as day 28 (1.33 ± 1.62 log(cfu/g)). Sensory evaluation revealed no significant differences (p > 0.05) between the coated and uncoated samples for color, appearance, texture, flavor, or overall acceptability. By valorizing a dairy by-product into an active, probiotic-loaded edible film, this approach offers a sustainable, waste-reducing strategy that enhances cheese preservation while delivering added functional value-bridging the gap between food packaging and nutrition. Sensory evaluation (n = 8, preliminary) indicated no significant differences between coated and uncoated samples, but these results require confirmation with a larger, validated panel.