Heat Tolerances of Salmonella, Cronobacter sakazakii, and Pediococcus acidilactici Inoculated into Galactooligosaccharide

Abstract

Food-grade galactooligosaccharide (GOS) with low water activity (a of ca. 0.7) is used as an ingredient in various foods. We evaluated heat tolerances of Salmonella, Cronobacter sakazakii, and Pediococcus acidilactici at temperatures (70 to 85°C) used during the saturation process of GOS by comparing decimal reduction time (D-values) and thermal resistance constants (z-values). To determine the D- and z-values, GOS containing Salmonella (5.1 to 5.8 log CFU/g) or C. sakazakii (5.3 to 5.9 log CFU/g) was heat treated at 70, 77.5, or 85°C for up to 40, 25, or 15 s, respectively, and GOS containing P. acidilactici (6.1 to 6.5 log CFU/g) was heat treated at 70, 77.5, or 85°C for up to 150, 75, or 40 s, respectively. The D-values were calculated using a linear model for heating time versus microbial population for each bacterium. When the D-values for Salmonella, C. sakazakii, and P. acidilactici in GOS were compared, the thermal resistance of all bacteria decreased as the temperature increased. Among the three bacteria, P. acidilactici had higher D-values than did Salmonella and C. sakazakii. The z-values of Salmonella, C. sakazakii, and P. acidilactici were 30.10, 33.18, and 13.04°C, respectively. Overall order of thermal resistance was P. acidilactici > Salmonella ≈ C. sakazakii. These results will be useful for selecting appropriate heat treatment conditions for the decontamination of pathogenic microorganisms during GOS manufacturing.

Invited review: Stress resistance of Cronobacter spp. affecting control of its growth during food production

“…are in general more heat tolerant than most Enterobacteriaceae; their heat tolerance varies between strains and growth conditions (Arroyo et al, 2009;Dancer et al, 2009). Because Cronobacter can survive at the temperature up to 64°C for 1 min (Huertas et al, 2015;Yang et al, 2015;Bang et al, 2017b), The World Health Organization-Food and Agriculture Organization of the United Nations recommends rehydration of PIF with water at least 70°C (WHO- FAO, 2008).…”