Whey protein isolate-lignin complexes as encapsulating agents for enhanced survival during spray drying, storage, and in vitro gastrointestinal passage of Lactobacillus reuteri KUB-AC5

Abstract

This study aimed to investigate the effect of encapsulant weight ratios of whey protein isolate (WPI)-lignin complex (10:0, 9.5:0.5, 9:1, 8.5:1.5, and 8:2) on survival of Lactobacillus reuteri KUB-AC5 during spray drying, storage, and passage through simulated gastrointestinal tract. Change in the secondary structure of WPI indicated its interaction with lignin. Higher lignin amounts resulted in higher yields and lower moisture contents. After spray drying and 2-month storage, the highest and lowest malondialdehyde contents were found in 10:0 and 9:1 formulations, respectively. After drying, the lowest and highest numbers of viable cells, 8.70 and 9.34 log CFU/g, were found in 10:0 and 9:1 formulations, respectively. After storage at 4 and 37 °C, the lowest and highest survival rates were also observed in these two formulations. At higher lignin concentrations, inactivation rate constants were reduced. After passage through simulated gastrointestinal tract, the highest and lowest cell viability was observed in 9:1 formulation and free cells, respectively. The results showed that microencapsulation using WPI-lignin complexes at 9:1 ratio offered the best protection. Lignin improved survival of spray-dried probiotics through improving the structure and antioxidant properties of WPI.