Synergistic Effects of Microalgae and Probiotic Additives in Edible Coatings on Strawberry Storage Quality: Experimental and Molecular Docking Studies.

This study investigates the addition of a probiotic (Lactobacillus plantarum 299v) and prebiotic microalgae (Arthrospira platensis) supporting the coating and its effectiveness in coating strawberries. As plasticizer and surface interface agent, 1.5% glycerol (v/v) and 1.5% sodium alginate (w/v) were used, respectively. Probiotic bacteria (10 CFU/mL) and Spirulina powder (w/v) (0.5%) were added into the coating solution. The molecular interaction Spirulina Rubisco and C-phycocyanin alpha and beta protein with sodium alginate was demonstrated using molecular docking analysis, highlighting key binding regions. Binding affinities were found to be -12.1 kcal/mol, -11 kcal/mol, and -9.9 kcal/mol, respectively, which indicates strong binding. The samples were prepared as uncoated strawberries (C), only sodium alginate as SA, sodium alginate and probiotics as SA+P, and sodium alginate, probiotics, and microalgae as SA+P+A. The pH values of film solutions were 8.67 ± 0.03 (SA), 7.33 ± 0.08 (SA+P), and 7.00 ± 0.01(SA+P+A). The total phenolic content of films was 0 mg GAE/100 g for SA, 6.479 ± 0.282 mg GAE/100 g for SA+P, and 76.761 ± 2.676 mg GAE/100 g for SA+P+A. During storage at 4 °C for 1 week, the microbiological and some physicochemical properties of the samples were analyzed. Additionally, lactic acid bacteria counts were conducted in the probiotic-added films. The pH and titratable acidity of each strawberry group were determined at the beginning and end of storage. It was observed that coating the strawberries with algae and probiotics delayed spoilage and better preserved the physical quality of the strawberries in the SA, SA+P, and SA+P+A samples compared to the control. The coating was effective in controlling yeast and mold growth. Furthermore, the film structure in probiotic-added films was found to protect probiotic bacteria. Citric acid level decreased in the control group while increasing in the others, which can be explained by the preservation and ripening of strawberries. In vitro gastrointestinal environment simulation showed that the viability of probiotics was 87.8%.