MECHANICALLY PROCESSING COTTONSEED TO REDUCE GOSSYPOL AND AFLATOXIN LEVELS

Authors: Buser, Michael; Abbas, Hamed

Submitted to: Journal of Toxicology Toxins Reviews
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/26/2001
Publication Date: 8/1/2001
Citation: Buser, M.D., Abbas, H.K. 2001. Mechanically processing cottonseed to reduce gossypol and aflatoxin levels. Journal of Toxicology Toxins Reviews. Vol. 20(3&4), 179-208.

Interpretive Summary: Cottonseed is an economic source of protein and is commonly used in balancing livestock rations. However, its use is typically limited by protein level, fat content, free-gossypol, and the potential for aflatoxin. Livestock rations containing higher than recommended rates of aflatoxin and/or gossypol can be toxic and even lethal. Gossypol levels in cottonseed are relatively constant but aflatoxin contamination widely varies. Aflatoxin contamination is extremely dependant on environmental conditions and location. When high infestation occurs, producers incur severe economic losses due to the extremely low marketability of the commodity. In fact, these contaminated commodities may become a disposal problem when rejected from the market. A review of the current literature on reducing gossypol and aflatoxin levels through mechanical processes was conducted. Based on previous research, gossypol and aflatoxin in cottonseed can be reduced over 70% and 50%, respectively, by extrusion under various combinations of pressure and temperature without adversely affecting nutritional value. Future research should be directed toward optimization of the extrusion process both operationally and economically. Success of this research will greatly increase the marketability of cottonseed products for animal and human consumption.

Technical Abstract: Cottonseed 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 the material was processed by two stages of extrusion at a temperature of 132 degrees C. Similar reductions have been reported on roasting corn at temperatures of 140 to 143 degrees C. 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.