Evaluation of the quince seed mucilage as an encapsulant for bioprotection of cultures during freeze-drying and digestion

Ensuring the viability of probiotic microorganisms during food processing, storage, and gastrointestinal transit remains a major challenge in food production. Encapsulation and coating methods have been developed to protect probiotics from these adverse conditions and enhance targeted delivery. Quince Seed Mucilage (QSM) is a plant-derived, polysaccharide-rich mucilage with high swelling capacity, biocompatibility, and responsiveness to pH and salt concentration, making it a promising protective matrix. This study investigated QSM as a potential smart coating material with pH_responsive properties for two lactic acid bacteria (LAB) strains: Lactobacillus plantarum MT4680 and Pediococcus pentosus M4336 using freeze-drying as a widely applied food-processing technique. Cell survivability and powder characteristics were evaluated for formulations containing QSM, either alone or combined with 15% skim milk. The most effective formulations were further assessed under simulated gastrointestinal conditions using the INFOGEST digestion model. QSM demonstrated notable cryoprotective activity during freeze-drying with the highest viability observed for 1% QSM combined with 15% skim milk (94 ± 17% immediately after freeze-drying and 91 ± 14% after one month of storage at 4°C). In comparison, survival rates for 1% QSM or 15% skim milk alone were significantly lower as evidenced by decreased viability during storage. Under simulated gastrointestinal conditions, QSM-containing formulations provided superior protection, with minimal log reductions of - 0.52 ± 0.24 in 1% QSM and -0.62 ± 0.14 in 1% QSM + 15% skim milk, representing over 100-fold higher fold cell protection than the uncoated cells. Rheological analysis demonstrated weak-gel behaviour and marked pH-dependent changes in the viscoelastic properties of QSM, supporting its potential as a smart coating material. These results demonstrate QSM’s effectiveness in preserving probiotic viability and reproductive capacity, highlighting its potential as a natural, biocompatible coating material for functional food application.