Methodology to Determine Destruction of Bacterial Spores during Extrusion Cooking

Abstract

ABSTRACT A methodology was developed for determining destruction of bacterial spores during extrusion cooking in a single screw extruder. Procedures were developed for estimating processing time at different screw speeds and calculation of “D‐” and “z‐values.” The proposed methodology evaluated destruction of Bacillus globigii spores in 18% moisture corn/ soybean mixture (70/30%, w/w). “D‐value” expressed on the basis of average time at mass temperature >95°C during extrusion was the most conservative estimate of spore sensitivity. Times ranged from 1.7 sec at 115°C to 6.6 sec at 100°C maximum mass temperatures. These “D‐values” resulted in a “z‐value” of 25.3°C., similar to that reported for the same strain with dry heat.