Microencapsulated Lactobacillus rhamnosus GG in whey protein and resistant starch matrices: Probiotic survival in fruit juice

This study compared the survival of spray dried microencapsulated Lactobacillus rhamnosus GG (LGG) added into apple juice or citrate buffer (pH 3.5) and stored at 4 or 25 °C over a 5-week period. The LGG was encapsulated in matrices comprising (i) whey protein isolate (WPI) alone, (ii) WPI in combination with a physically-modified resistant starch (RS) at various ratios (4:1, 1:1 and 1:4), or (iii) RS alone. All microencapsulated LGG formulations containing WPI alone or WPI in combination with RS provided better protection to LGG in apple juice or citrate buffer compared to the formulation containing RS alone. We suggest that the protection afforded by formulations containing WPI alone or in combination with RS is due to the ability of WPI to create a buffered microenvironment within the hydrated colloid particle surrounding the embedded LGG, thus isolating the bacteria from the stresses of the low pH external environment.