Ps. Fernandez et al., D VALUES OF BACILLUS-STEAROTHERMOPHILUS SPORES AS A FUNCTION OF PH AND RECOVERY MEDIUM ACIDULANT, Journal of food protection, 58(6), 1995, pp. 628-632
The effect of the pH and the type of acidulant (citric acid or glucono
-delta-lactone) of the recovery medium on the thermal resistance of Ba
cillus stearothermophilus ATCC 12980 was studied. The spores were heat
ed in bidistilled water as a reference substrate and in acidified mush
room extract using citric acid or glucono-delta-lactone as acidulants
(pH 6.2) and subcultured in reference (pH 7) and acidified (pH 6.2) me
dia. A period of treatment-dependent pH sensitization was observed in
heat-treated spores. In all cases, D values were lower in the acidifie
d recovery medium than those obtained in the reference medium, but the
type of acidulant used in the recovery medium had no influence on the
D values. No influence on z values was observed as a consequence of t
he different recovery media, but they changed within a range of 7 to 1
0 degrees C as a function of the different heating substrates. Glucono
-delta-lactone proved to be as effective as citric acid in controlling
the microbiological spoilage of foods. The pH has a great influence o
n decreasing the D values, mainly when acidification of the substrate
and acidification of the recovery medium are combined. Consequently, i
t would be appropriate to take this effect into account in process cal
culations or validation.