Encapsulation of Lactobacillus casei in quince seed gum-alginate beads to produce a functional synbiotic drink powder by agro-industrial by-products and freeze-drying

A new functional synbiotic drink powder based on plant by-products (grape pulp, pomegranate and beetroot peels extracts), Lactobacillus casei, and the use of microencapsulation (by quince seed gum (QSG) and sodium alginate (Alg)) and freeze-drying technologies were produced and characterized. Evaluation of the functional properties of drink powders showed that the total phenolic content (TPC), oxygen radical absorbance capacity (ORAC) and DPPH radical scavenging activity were in the range of 19.78–21.35 mg GAE/g, 193.45–194.19 μmol TE/g and 67.34–71.14%, respectively. After freeze drying process, probiotic survival rate in the functional drink powders containing free Lactobacillus casei (FDP1) was 42.16%, and increased to 86.40% and 87.56% in the powders containing probiotic Alg-microcapsules (FDP2) and probiotic Alg-QSG microcapsules (FDP3), respectively. The production yield, moisture content, solubility, wettability, lightness, redness and yellowness of the drink powders (FDP1-3) were in the range of 10.95–13.16%, 4.94–5.17%, 85.25–88.29%, 21.56–22.12s, 51.86–53.70, 20.13–22.35 and 1.95–2.13, respectively. Based on the results, the Alg-QSG microcapsules maintained the L. casei viability of the recommended level of 106−7 CFU/g during the storage period of 60 days and made the drink powder (FDP3) as a functional synbiotic product.