Effects of extrusion temperature and dwell time on aflatoxin levels in cottonseed.

Cottonseed is an economical source of protein and is commonly used in balancing livestock rations; however, its use is typically limited by protein, fat, gossypol, and aflatoxin contents. Whole cottonseed was extruded to determine if the temperature and dwell time (multiple stages of processing) associated with the process affected aflatoxin levels. The extrusion temperature study showed that aflatoxin levels were reduced by an additional 33% when the cottonseed was extruded at 160 degrees C as compared to 104 degrees C. Furthermore, the multiple-pass extrusion study indicated that aflatoxin levels were reduced by an additional 55% when the cottonseed was extruded four times as compared to one time. To estimate the aflatoxin reductions due to extrusion temperature and dwell time, the least mean fits obtained for the individual studies were combined. Total estimated reductions of 55% (three stages of processing at 104 degrees C), 50% (two stages of processing at 132 degrees C), and 47% (one stage of processing at 160 degrees C) were obtained from the combined equations. If the extreme conditions (four stages of processing at 160 degrees C) of the evaluation studies are applied to the combined temperature and processing equation, the resulting aflatoxin reduction would be 76%.