Thermal resistance ofAlicyclobacillus acidoterrestrisspores in different buffers and pH

Abstract

The influence of buffers and pH on the thermal resistance of a novel flat sour-type of spoilage bacterium,Alicyclobacillus acidoterrestris, was investigated. At a low concentration (20 mM), decimal reduction times (D-values) in citrate and phosphate buffers were 13.6 and 12.9 min, respectively, showing little variation. At a high concentration (100 mM), however, theD-value in citrate buffer, 14.4 min, was significantly higher than that in the phosphate buffer, 12.3 min.D-values in McIlvaine buffers did not vary widely within the pH range of 3.0 to 8.0. At 88, 90, 92 and 95°C in McIlvaine buffers,D-values were 24.1–29.1, 14.8–16.8, 5.7–7.1 and 2.2–2.8 min, respectively. The thermal resistance ofA. acidoterrestrisspores was affected very little by varying the pH of the heating menstruum. TheZ-values also did not vary widely as the pH varied among the different buffers, ranging from 6.4 to 7.1°C. It was evident thatA. acidoterrestrisspores showed a special relationship, unknown among other bacterial spores, between their thermal resistance and the pH of the heating menstruum. Therefore,A. acidoterrestrisshould be targeted when the quality of acidic food products is being tested.