Curdlan as a heat-irreversible gel wall material in electrostatic spray-dried solid/oil/water probiotic microcapsules: Thermal resistance and storage stability.

In this study, to develop a robust probiotic delivery system, high molecular weight 1,3-β-D-glucan curdlan gum (CUR) was employed as a functional wall material. It was combined with whey protein isolate and high oleic sunflower oil to prepare solid/oil/water (S/O/W) emulsion microcapsules using electrostatic spray drying (ESD) technology. Additionally, pectin and high oleic sunflower oil were utilized as functional wall materials. All the microcapsules exhibited low water content (3.66%-5.04%) and water activity (aw 0.178-0.230), which is beneficial for long-term storage stability. Following drying, the survival rate of probiotics in each treatment group exceeded 90%. It is worth noting that the microcapsules containing 5% CUR exhibit the most effective overall protective effect: following heat treatments of 63 °C for 30 min and 75 °C for 10 min, the loss of viable bacteria was only 1.18 and 1.39 Log CFU/g, respectively. After 12 weeks of storage at 4 °C and 25 °C, the survival rates were maintained at 93% and 66%, respectively. Its excellent performance is attributed to the fact that CUR can form a dense gel network structure at high temperatures, which effectively blocks heat transfer and oxygen penetration. Scanning electron microscopy and Fourier-transform infrared spectroscopy confirmed that microcapsules containing 5% CUR form a relatively dense physical barrier and maintain structural integrity. The above results demonstrate that incorporating CUR into a S/O/W emulsion system, combined with ESD technology, is a promising strategy for wall materials to enhance the thermal tolerance and shelf-life stability of probiotic microcapsules.