THERMAL-RESISTANCE CHARACTERISTICS OF PA-3679 IN THE TEMPERATURE-RANGE OF 110-121-DEGREES-C AS AFFECTED BY PH, TYPE OF ACIDULANT AND SUBSTRATE

The influence of mushroom extract, acidification and type of acidulant (citric acid or glucono-delta-lactone) on the thermal resistance of PA 3679 spores has been studied. The pH values were 7 (phosphate buffer), 6.7 (non acidified mushroom extract), 6.22, 5.34 and 4.65 (acidified mushroom extract). Spores were less heat resistant in the non-acidified mushroom extract than in phosphate buffer. However, acidification of the extract had an effect on D values which was dependent on the specific pH. At pH 6.22, D values were higher than those in non-acidified extract, for both type of acidulants, but the difference between D values in both substrates was affected by temperature, the higher the temperature, the less the difference. Acidification at other pH levels did not significantly affect D values obtained, neither did the type of acidulant. The z value ranged from 9.79 to 12.09-degrees-C for citric acid and from 8.18 to 10.18-degrees-C for glucono-delta-lactone. When pH was decreased the z value increased for both acidulants.