Effect of skimmed milk powder concentrations on the biological characteristics of microencapsulated Saccharomyces cerevisiae by vacuum-spray-freeze-drying
Lin Cao, Qinglian Xu, Yage Xing, Xunlian Guo, Wenxiu Li, Yimin Cai
The effects of skimmed milk powder (SMP) concentrations on the biological characteristics of microencapsulated Saccharomyces cerevisiae prepared by employing vacuum-spray-freeze-drying (VSFD) technology are evaluated. Results show that the live bacteria rate of S. cerevisiae embedded with 11% SMP is 76.36%, which is higher than that in other concentrations. Scanning electron microscope (SEM) photographs indicate that the SMP concentration exhibits a significant impact on the surface morphology of microencapsulation. Moreover, microparticles with SMP at the concentration of 11% provide the highest stability levels in both high and low temperature conditions. Cell counts in the microparticles with 11% SMP show a reduction of 3.9 (60 °C, 20 min) log CFU mL⁻¹, 3.13 (50 °C, 20 min) log CFU mL⁻¹, 0.23 (40 °C, 20 min) log CFU mL⁻¹, 2.74 (4 °C, week) and 0.72 (10 °C, week) log CFU mL⁻¹, respectively, which are all lower than that of powders with 3% SMP. Furthermore, the best-quality icewine exhibiting the typical features of a fresh fragrance and a delicate taste is used for the in vivo fermentation process. Fermentation is initialized by the microencapsulated cells with 11% SMP. These results indicate that the complex materials containing an SMP concentration of 11% as a carrier can be considered as a better choice for improving the stability and survival rate of S. cerevisiae.