Investigation of Multilayer Edible Probiotic Coatings During Refrigerated Storage of Strawberries: A Focus on Lacticaseibacillus casei Shirota and Lacticaseibacillus rhamnosus GG

The layer-by-layer (LBL) coating technique is an emerging alternative to conventional dipping for active packaging, improving coating adhesion to the hydrophilic surface of fruits. This study assessed the effects of probiotic multilayer coatings on microbial quality, physicochemical properties, and sensory attributes of strawberries stored in macro-perforated PET trays at 4 °C for 14 days. Strawberries were coated using a five-step LBL dipping process with alternating layers of 1% CaCl2 and 1% sodium alginate (SA). Strawberries coated with an LBL probiotic coating containing either Lacticaseibacillus casei Shirota (EC-LC) or Lacticaseibacillus rhamnosus GG (EC-LR), uncoated strawberries, and strawberries multilayer-coated with SA without probiotics (EC) were studied. Both probiotic-enriched coatings similarly inhibited (p ≥ 0.05) weight loss, decay, and TSS accumulation, thereby delaying ripening, while EC-LC improved the firmness of strawberries. Moreover, EC-LC was the most effective treatment in minimizing changes in sugars and organic acid concentrations. All coated samples showed a smaller decline in the a* parameter (redness) than controls, while EC-LC reached the highest values of lightness during storage, indicating a glossier appearance of the product. Fungal growth was inhibited by ca. 2.0 log CFU/g in EC-LC and EC-LR samples, while the embedded probiotic cultures remained viable, with counts near 106 CFU/g of fruit during storage at 4 °C. Finally, sensory evaluation showed that uncoated strawberries became unacceptable by day 9, whereas EC-LC fruits remained acceptable in terms of odor and color attributes until day 14. Overall, it seems that the studied probiotic multilayer coatings, especially EL-LC, may offer new perspectives for extending the shelf-life of strawberries, while also providing them with functional properties.