Effects of Extrusion Temperature and Dwell Time on Aflatoxin Levels in Cottonseed

Authors: Buser, Michael; Abbas, Hamed

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2002
Publication Date: 5/1/2002
Citation: Buser, M.D., Abbas, H.K. 2002. Effects of Extrusion Temperature and Dwell Time on Aflatoxin Levels in Cottonseed. Journal of Agricultural and Food Chemistry. 50(9):2556-2559.

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 can be toxic and even lethal. Aflatoxin contamination widely varies and is extremely dependent on environmental conditions and location. When high infestation occurs, producers incur severe economic losses due to the extremely low marketability of the commodity. To solve this problem, cottonseed was extruded under high pressure and shear forces, resulting in high internal extruder temperatures, to determine if the process would reduce aflatoxin levels. Results show that aflatoxin levels are substantially impacted by increases in extrusion temperature and material dwell time. Based on the findings of this study, further research should be conducted to determine the optimum extruder parameters required to achieve the largest aflatoxin reductions while maintaining economic feasibility. The ability to utilize a relatively low cost process such as extrusion to reduce aflatoxin contamination could economically benefit producers, especially when moderate contamination occurs.

Technical Abstract: 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 content. 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 sequentially reduced 20% for each 20 degrees C increase in temperature. Further, the multiple pass extrusion study indicated that aflatoxin levels were sequentially reduced by about 23% for each additional stage of processing. Combining the least square means fits obtained from the studies, reductions of 55% (3 stages of processing), 50% (2 stages of processing), and 47% (1 stage of processing) for processing temperatures of 104, 132, and 160 degrees C, respectively. If the extreme conditions (4 stages of processing at 160 degrees C) of the evaluation studies are applied to the combined temperature and processing equation, the aflatoxin is reduced 76%.