Kinetics and Thermodynamics of Gossypol Extraction from Defatted Cottonseed Meal by Ethanol Acidified by Oxalic Acid

Cotton crop is grown to meet the basic requirement of fabrics. After de-linting the cotton ball, seed is left which is a good source of oil approx.18 % and protein approx.25 %. After extraction of oil from the seed, the left over cake is a rich source of good quality protein but presence of gossypol, a highly toxic substance, makes it unfit for human consumption. A number of earlier attempts to extract gossypol from the seeds using different solvents have been made to reduce the gossypol content within the prescribed maximum FDA limit of 450 ppm. In most of the cases, gossypol extraction had been carried out at low temperatures to minimize its binding with lysine (an essential amino acid present in the protein of the seed), as higher temperature accelerated the binding process which resulted in reduced digestibility of the protein. Ethanol acidified with mild organic acids has been reported to prevent complexing of gossypol with lysine at relatively higher temperatures. Present studies are undertaken to extract gossypol from the defatted cotton seed meal using green solvent (ethanol) acidified by mild organic oxalic acid at temperatures up to 343K to improve extraction efficiency. Up to 92.4 % gossypol could be extracted from the defatted cottonseed meal using acidic ethanol as against 61.55 % extraction with pure ethanol thus making the seed meal suitable for food uses. The data obtained were analyzed to establish kinetics and thermodynamics of the extraction process which would be helpful in scaling up the process to pilot/ commercial scale.