Mechanically processing cottonseed to reduce gossypol and aflatoxin levels

Cottonseed is an economical source of protein and is commonly used in balancing livestock rations; however, its use is typically limited by protein level, fat content, gossypol, and the potential for aflatoxin contamination. There are numerous studies in the literature discussing gossypol and aflatoxin toxicities in livestock and processing methods for reducing gossypol levels in cottonseed. However, there is very limited information in the literature within the last 30 years on how aflatoxin is affected by processing. Evaluation studies were conducted to determine if an extrusion process affected gossypol and aflatoxin levels in cottonseed without negatively impacting the nutritional value of the product, and if these reductions were consistent with the literature. Results from the gossypol study showed a 71 to 78% decrease in free gossypol levels due to the extrusion process, which were lower than some reported methods of processing and consistent with others. Results from the aflatoxin studies showed reductions of 50% when thematerial was processed by two stages of extrusion at a temperature of 132degreesC. Similar reductions have been reported on roasting corn at temperatures of 140 to 143degreesC. The extrusion temperatures used in the evaluation studies did not significantly alter most of the nutritional values analyzed in the study. However, soluble protein was decreased at the higher temperatures. There were no significant differences in analyzed nutritional values based on multiple stages of processing. Results from the evaluation study indicate that extruding cottonseed to reduce gossypol and aflatoxin levels is an area of research that should be further explored, primarily due to the advances made in the aflatoxin and gossypol testing methods during the last 30 years.