Synbiotic edible film from konjac glucomannan composed of Lactobacillus casei-01® and Orafti®GR, and its application as coating on bread buns

BACKGROUND Konjac glucomannan-based edible films formulated with Lactobacillus casei-01® and chicory-derived inulin Orafti®GR were studied for their properties, stability, and application as coatings on bread buns. RESULTS Thickness and transparency were variable and dependent on the formulations. Alterations in color properties of all supplemented films were unnoticeable by unaided human eyes, with ΔE less than 3. Lactobacillus casei-01® and Orafti®GR were associated with higher water solubility of the films. Lactobacillus casei-01® decreased the water vapor permeability of the films while Orafti®GR promoted it. The mechanical properties in all combinations remained unchanged, although those with Orafti®GR showed profoundly reduced tensile strength. Scanning electron micrographs and Fourier transform infrared spectra of the films confirmed good homogeneity and intermolecular attraction between the prebiotic and konjac glucomannan. Cell viability in the films stored at room temperature decreased sharply, becoming less than the minimum recommended level after day 4, while viable L. casei-01® in coatings on bread buns gradually decreased, with a reduction of ca. 2 log colony-forming units (CFU) portion-1 over the 7 day storage period at room temperature. CONCLUSION The synbiotic film and coating developed in this study are a relatively simple strategy for incorporating L. casei-01® and Orafti®GR into bread buns, which are short shelf-life foods. Bread buns with synbiotic coating could diversify functional food choices. Pretreatment, together with other technologies, is required to maintain a desirable number of active probiotic cells for longer. © 2020 Society of Chemical Industry.