Bioactive edible film based on Konjac glucomannan and probiotic Lactobacillus plantarum strains: Physicochemical properties and shelf life of fresh‐cut kiwis

Abstract

This study investigates the efficacy of Lactobacillus plantarum strains (L. plantarum LP3, L. plantarum AF1, and L. plantarum LU5) incorporated into a Konjac‐based edible coating in order to prevent fungi growth and retain physicochemical characteristics of fresh‐cut kiwis kept at 4 °C for 5 days. For this purpose, probiotic survivability, fungi counts, decay percentage, color changes, titratable acidity (TA), total soluble solids (TSS), ascorbic acid content, chlorophyll amount, total phenolics, and DPPH radical scavenging of fresh‐cut kiwis were evaluated. Results indicated that the population of L. plantarum strains in all treated groups retained at sufficient amounts of probiotic consumption (above 6 and 7 log CFU/g) at the end of the storage period and L. plantarum LP3 had the highest viability in comparison to other strains. The incorporation of L. plantarum in Konjac coatings markedly reduced the amount of decay and color changes and maintained the chlorophyll and ascorbic acid contents of fresh‐cut kiwis compared to control samples. After 5 days of storage, total phenol content and the DPPH antiradical activities of coated kiwi slices treated with probiotics were observed about 1.2 and 10.23 g/kg compared to the pure Konjac‐coated (0.84 and 7.6 g/kg) and Konjac‐uncoated samples (0.44 and 4.1 g/kg), respectively. No significant difference in TSS and TA of various treatments was detected. Coated kiwi slices loaded with probiotics had higher overall acceptability compared to Konjac‐coated and control samples. In addition, probiotic treatment significantly reduced mold and yeast counts compared to the control group.Practical ApplicationsRecently, edible films have received more consideration as a promising method to enhance the shelf life of fresh‐cut fruit. The presence of probiotics in edible films reduces the growth of spoilage microorganisms and improves consumer health. Our findings encourage the application of edible coating incorporated with L. plantarum to design multifunctional foods and preserve the qualities of fresh‐cut kiwifruit.

Current Advances on the Development and Application of Probiotic-Loaded Edible Films and Coatings for the Bioprotection of Fresh and Minimally Processed Fruit and Vegetables

“…The selection of a plasticizer for edible film/coating formulation should consider the adaptability and persistence of the plasticizer, as well as the required physical characteristics for the developed film/coating. Glycerol has been the plasticizer most frequently used to formulate films/coatings to be applied on fruit and vegetables [ 2 , 20 , 23 , 28 ], providing increased moisture content and gas permeability to these structures when compared to other plasticizers (e.g., sorbitol) [ 35 ].…”

“…Despite the potential benefits of the incorporation of probiotics into edible films/coatings to preserve fruit and vegetables, there are still some limitations for the efficacy of their use related to the survival of probiotics entrapped in these composite materials. The concentration of probiotic cells entrapped in edible films/coatings may suffer large variations during the film/coating preparation, storage condition and gastrointestinal digestion, which could negatively affect their food preservative and health-related biological properties [ 2 , 10 , 11 ].…”

“…The antimicrobial effects of probiotic-loaded edible films/coatings when applied to fruit and vegetables in different studies are shown in Table 3 . In addition to evaluating the effects of probiotic-loaded films/coatings on the autochthonous microbiota of fruit and vegetables [ 2 , 6 , 18 ], some studies have also used artificial contamination with pathogenic (e.g., Listeria innocua and Escherichia coli O157:H7) [ 22 , 29 ] or spoilage microorganisms (e.g., Botrytis cinerea ) [ 26 ].…”

“…Freshly processed kiwi fruit coated with konjac gum and L. plantarum strains had reduced counts of molds and yeasts than uncoated fruit after 5 days of refrigeration storage [ 2 ]. Gelatin-based coating with L. rhamnosus and inulin reduced the counts of molds and yeasts and mesophilic bacteria in strawberries during 16 days of refrigeration storage [ 12 ].…”

“…However, the quality and safety of fruit and vegetables typically decrease during the postharvest processing due to their high moisture content, ripening, senescence, microbial growth and environmental factors. The minimal processing may also cause physical damage and enhance the ethylene production in fruit and vegetables, accelerating their ripening and senescence [ 2 ]. These factors increase the postharvest losses in fruit and vegetables, which can reach up to 25–40% before the final consumption [ 3 , 4 ].…”