UPDATE ON THE IMPACT OF DRY EXTRUDING COTTONSEED TO REDUCE AFLATOXIN AND GOSSYPOL LEVELS

Authors: Buser, Michael; Abbas, Hamed

Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/9/2001
Publication Date: 6/1/2001
Citation: Buser, M.D., Abbas, H.K. 2001. Update on the impact of dry extruding cottonseed to reduce aflatoxin and gossypol levels. National Cotton Council Beltwide Cotton Conference. Vol. 2: 1392-1403.

Interpretive Summary: Cottonseed is an economic source of protein and is commonly used in balancing livestock rations. However, its use is limited by protein level, fat content, free-gossypol, and the potential for aflatoxin. Aflatoxin and free-gossypol are substances, which can be toxic and even lethal to livestock when fed at higher than recommended rates. While gossypol levels sin cottonseed have remained relatively constant over the past 40 or more years, aflatoxin contamination varies widely from year to year. The level of aflatoxin contamination is extremely dependant on environmental conditions, location, and agricultural commodity. When high infestation occurs, producers incur severe economic losses due to the extremely low marketability of the commodity. In order to help solve the aflatoxin problem, cottonseed and mixtures containing cottonseed were extruded under high pressure and shear forces, resulting in high internal extruder temperatures, to determine if the process would reduce gossypol and aflatoxin levels without lowering the nutritional value of the product. Results indicated that free-gossypol levels were substantially reduced in mixtures of cottonseed and cotton gin by-products and the nutritional value of the extruded product increased with increasing levels of cottonseed. The extrusion process decreased the inherent variability associated with aflatoxin contamination and decreased the overall aflatoxin levels of the contaminated cottonseed. Further research is required to determine the optimum extruder parameters required. The ability to utilize a relatively low cost process such as dry-extrusion to reduce aflatoxin contamination could economically benefit producers, especially when moderate contamination occurs.

Technical Abstract: 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, gossypol, and the potential for aflatoxin. Cottonseed and mixtures of cottonseed and cotton gin by-products (CGBP) were extruded at relatively high temperatures to determine if the process would reduce the free-gossypol and aflatoxin levels in the material, without degrading the nutritional value of the original material. Results indicated a 71 to 78% reduction in free gossypol levels for the various mixing ratios, based of the official AOCS standard methods. This reduction is most likely under estimated, since the official methods for determining free-gossypol levels are not specific to gossypol and constituents from other feed ingredients can interfere with the spectrophotometric determination. Cottonseed with aflatoxin levels in excess of 650 ppb was used to determine the effect of extrusion temperature and increased processing on the aflatoxin and nutritional values of the contaminated cottonseed. The variability of aflatoxin in contaminated lots is extremely high. Results for the test on extrusion temperature indicated that aflatoxin levels decrease as the extrusion temperature increases. Soluble protein was significantly decreased at the higher temperatures. Results from this study indicate that dry-extruding cottonseed to reduce gossypol and aflatoxin levels is an area of research which should be further explored.