Survival of Freeze Dried Lactic Acid Bacteria Isolated from Breast Milk During Reconstitution and Their Ability to Compete with Cronobacter sakazakii.

Abstract

Powdered infant formula (PIF) is a fabricated food product whose nutrition is formulated to correspond to breast milk. Nowadays, some PIF manufacturers have supplemented PIF with probiotic bacteria. However, due to possible Cronobacter spp. contamination, reconstitution at 70 oC is adviced thus it may also affect the viability of lactic acid bacteria (LAB). The objective of this study was to evaluate the survival of freeze dried LAB isolated from breast milk during reconstitution and their ability to compete with Cronobacter sakazakii (C. sakazakii) in PIF. This study was conducted in 4 stages, i.e. (1) screening of LAB isolates based on the survival during reconstitution at 50 oC; (2) competition of LAB isolates with C. sakazakii YRC3a; (3) evaluation of the LAB isolates on freeze drying process; and (4) competition of LAB isolates with C. sakazakii YRC3a in PIF at various reconstitution temperatures. Screening of LAB showed that all LAB isolates decreased in cell number after reconstitution at 50 oC. Based on the result of screening, 4 LABs were chosen i.e Lactobacillus rhamnosus (L. rhamnosus) R14, R21, R23, and R25 because the bacterial number decrease was lower. However, only L. rhamnosus R21 and R25 were capable of inhibiting the growth of C. sakazakii YRC3a. Meanwhile, assessment of the LAB survival during freeze drying process showed insignificant reduction of cell number of L. rhamnosus R21 and R25. Competition of freeze dried L. rhamnosus R21 and R25 with C. sakazakii YRC3a during reconstitution in PIF at various reconstitution temperatures (50, 60, and 70 oC) showed that the freeze dried LAB were able to suppress the number of C. sakazakii YRC3a as the temperature increased. The result also showed that LAB isolates did not undergo significant cell reduction as the reconstitution temperature increased.