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 P A 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 (acidifie d mushroom extract). Spores were less heat resistant in the non-acidif ied mushroom extract than in phosphate buffer. However, acidification of the extract had an effect on D values which was dependent on the sp ecific pH. At pH 6.22, D values were higher than those in non-acidifie d extract, for both type of acidulants, but the difference between D v alues in both substrates was affected by temperature, the higher the t emperature, the less the difference. Acidification at other pH levels did not significantly affect D values obtained, neither did the type o f acidulant. The z value ranged from 9.79 to 12.09-degrees-C for citri c acid and from 8.18 to 10.18-degrees-C for glucono-delta-lactone. Whe n pH was decreased the z value increased for both acidulants.