Title: Comparison of aluminum thermal-death-time disks with a pilot-scale pasteurizer on the thermal inactivation of Escherichia coli K12 in apple cider Authors
Submitted to: Food Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 20, 2008
Publication Date: February 1, 2009
Citation: Yuk, H., Geveke, D.J., Zhang, H.Q., Jin, Z.T. 2009. Comparison of aluminum thermal-death-time disks with a pilot-scale pasteurizer on the thermal inactivation of Escherichia coli K12 in apple cider. Food Control. 20:1053-1057. Interpretive Summary: Laboratory scale test methods have been used as a substitute for pilot-plant scale pasteurizers, to study the thermal inactivation of microorganisms in juice, because pilot-plant scale pasteurizers are expensive and labor intensive. However, objective comparisons between pilot-plant scale pasteurizers and laboratory scale methods are lacking. This study compared conventional glass tube and aluminum thermal-death-time (TDT) disk methods to a pilot-plant scale pasteurizer. Results show that the pasteurizer had similar effect at killing Escherichia coli in apple cider than the two laboratory methods at 60C. This investigation suggests that TDT disks are a useful tool to study thermal inactivation of Escherichia coli in apple cider.
Technical Abstract: This study was conducted to compare thermal inactivation kinetics of Escherichia coli K12 in apple cider using conventional glass tubes, aluminum thermal-death-time (TDT) disks, and a pilot-scale pasteurizer. D-values of E. coli K12 in glass tubes and TDT disks were determined at 56, 58, and 60C. D-values in the pasteurizer were calculated at the average temperatures of 58, 60, and 61C. The inlet and outlet holding tube temperatures were different due to heat loss during transit in the holding tube and were averaged. Come-up times at 58C were 35, 106, and 61 s for TDT disk, glass tube, and pasteurizer, respectively. Regardless of heating apparatus, D-values significantly (P < 0.05) decreased as treatment temperature increased. D-values in glass tube, TDT disk, and pasteurizer were 1.89, 1.44, and 3.11 min at 58C, and 0.67, 0.44, and 0.69 at 60C, respectively. Thermal inactivation by glass tube produced significantly (P < 0.05) higher z-value (5.74C) than TDT disk (4.46C) and pasteurizer (4.35C). This study indicates that TDT disks are useful to estimate the thermal inactivation kinetics of E. coli K12 in apple cider due to similar z-value and come-up time with a pilot-scale pasteurizer.