Effect of gums on viability and β-galactosidase activity of Lactobacillus spp. in milk drink during refrigerated storage

Summary The viability and β‐galactosidase activity of four Lactobacillus strains in milk drink containing gums during 28 days of refrigerated storage at 4 °C were assessed. The population of Lactobacillus rhamnosus GGB101 and Lactobacillus rhamnosus GGB103 were maintained, whereas the population of Lactobacillus reuteri DSM20016 and Lactobacillus reuteri SD2112 significantly decreased. The recommended level of 6 log CFU g−1 was exceeded for all tested trains throughout storage. The highest viable number of Lactobacillus rhamnosus GGB103 (8.76 ± 0.03 log CFU mL−1) was obtained in the product containing carrageenan–maltodextrin. The addition of guar–locust bean–carrageenan led to 20‐fold increase in the level of β‐galactosidase activity for L. rhamnosus GGB101 (1208 ± 2.12 Miller units mL−1) compared to the control (61 ± 2.83 Miller units mL−1). Our results suggested that gums could be added to milk to improve viability and enhance β‐galactosidase activity of Lactobacillus. During 28 days storage period, the population of Lactobacillus strains increased in the presence of gums compared to control. The highest viable number of Lactobacillus rhamnosus GGB103 was obtained in the product containing carrageenan‐maltodextrin. The addition of guar‐locust bean‐carrageenan led to an enhanced β‐galactosidae activity for L. rhamnosus GGB strains compared to the control.