Kefir-enriched alginate coating for fresh-cut apples: a natural biopreservation strategy to enhance microbial stability and produce quality

The growing demand for fresh-cut chemical-free fruits has driven the search for natural preservation strategies. This study explores the use of alginate-based edible coating enriched with kefir culture to maintain the quality and safety of fresh-cut apples. Pink Lady^® apple slices were subjected to these dipping treatments: water as a control (CTRL), 2% sodium alginate (ALG), or 2% alginate supplemented with a commercial kefir culture (ALG+KEFIR). Samples were stored at 4 °C for 7 days. Quality was assessed through microbiological analysis (mesophilic bacteria, yeasts and molds, and lactic acid bacteria), respiration rate, and visual appearance. Initially, all treatments exhibited similar respiration rates. However, by day 3, ALG showed a sharp increase (10.7 mL CO₂ kg^-1·h^-1), whereas ALG+KEFIR moderated this rise. By day 7, CTRL had the highest respiration, while ALG+KEFIR remained significantly lower. ALG+KEFIR also maintained the lowest mesophilic (3.24 log CFU g^-1) and fungal loads (3.3 log CFU g^-1), while supporting the highest LAB counts (3.1 log CFU g^-1). Visual quality was best preserved in ALG+KEFIR samples, with reduced browning. Incorporating kefir into alginate coatings enhances microbial stability and preserves visual quality. This natural, clean-label approach aligns with consumer preferences and offers a promising alternative to synthetic preservatives in fresh-cut fruit processing.