Influence of controlled atmosphere on thermal inactivation of Escherichia coli ATCC 25922 in almond powder. (June 2017) - Cheng, Teng
Abstract: Heat controlled atmosphere (CA) treatments hold potential to pasteurize Salmonella enteritidis PT 30 in almonds. Nonpathogenic Escherichia coli ATCC 25922 was used as a surrogate species of pathogenic Salmonella for validation of thermal pasteurization to meet critical safety requirements. A controlled atmosphere/heating block system (CA-HBS) was used to rapidly determine thermal inactivation of E. coli ATCC 25922. D- and z- values of E. coli ATCC 25922 inoculated in almond powder were determined at four temperatures between 65 °C and 80 °C under different gas concentrations and heating rates. The results showed that D- and z- values of E. coli under CA treatment were significantly ( P < 0.05) lower than those under regular atmosphere (RA) treatment at 4 given temperatures. Relatively higher CO2 concentrations (20%) and lower O2 concentrations (2%) were more effective to reduce thermal inactivation time. There were no significant differences in D- values of E. coli when heating rates were above 1 °C/min both in RA and CA treatments. But D- values significantly ( P < 0.05) increased under RA treatment and decreased under CA treatment at lower heating rates. Combination of rapid heat and CA treatments could be a promising method for thermal inactivation of S. enteritidis PT 30 in almond powder. Highlights: Thermotolerance of E. coli was determined using a CA-HBS. D- and z- values of E. coli under CA were significantly lower than those under RA. 20% CO2 /2% O2 were effective to reduce thermal inactivation time. Heating at 0.1 °C/min achieved highest inactivation in CA but lowest in RA treatments.