ARS | Publication request: Comparison of thermal inactivation kinetics of E. coli K12 in apple cider using conventional glass tubes, aluminum thermal-death-time disks, and a pilot-scale pasteurizer

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: April 7, 2008
Publication Date: June 28, 2007
Citation: Yuk, H., Geveke, D.J., Zhang, H.Q., Jin, Z.T. 2007. Comparison of thermal inactivation kinetics of E. coli K12 in apple cider using conventional glass tubes, aluminum thermal-death-time disks, and a pilot-scale pasteurizer. [astract]. Institute of Food Technologist. (IFT) Annual Meeting. p. 1.

Technical Abstract: To estimate thermal inactivation rates of microorganisms in food, heating apparatuses of bench-top scale such as glass tubes, capillary tubes, and aluminum disks have been developed and tested. However, little work has been done on comparing the thermal inactivation of microorganisms obtained by bench-top scale test methods to that obtained using pilot-plant scale pasteurizers. Therefore, this study was conducted to evaluate the difference among conventional glass tube, novel aluminum thermal-death-time (TDT) disk, and pilot-plant pasteurizer methods on the thermal inactivation kinetics of E. coli in apple cider. Glass tubes (13-mm OD x 100-mm length) or TDT disks (17-mm ID x 4-mm length) with 1 ml of inoculated apple cider were completely submerged in a water bath at 56, 58, and 60C to determine D-values. D-values of E. coli K12 from a pilot-scale pasteurizer equipped with a plate heat exchanger were determined 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 of the glass tube, TDT disk, and pasteurizer were 106, 35, and 61 sec at 58C, respectively. Regardless of heating apparatus, D-values significantly (P < 0.05) decreased as treatment temperature increased. D-values were 1.89, 1.44, and 3.11 min at 58C, and 0.67, 0.44, and 0.69 at 60C in glass tube, TDT disk, and pasteurizer, respectively. There was no significant (P > 0.05) difference in the z-values between TDT disks (4.46C) and pasteurizer (4.35C), and a significant (P < 0.05) difference in the z-value between these and the glass tube (5.74C). 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.