Modified procedures for determination of gossypol pigments. II. Determination of free gossypol in low gossypol meals and of gossypol in oils

Abstract Much of the «free» gossypol in meals of low free gossypol content consists of «soluble‐bound» gossypol. Addition of dilute hydrochloric acid reduces the optical densities of gossypol blanks in free and total gossypol calibrations and assays. The reductions in these optical densities were lower than expected in free gossypol assays on meals of lower free gossypol content. The soluble‐bound gossypol in these can be converted into gossypol by heating the extracts with dilute acid at 100C. This does not affect the optical densities of the nongossypol pigments, nor does it affect the optical densities obtained on heating with aniline. The procedure affords more accurate analyses for these meals. A similar modification has been developed for gossypol in oils.