Prepress‐solvent extraction of cottonseed, processing conditions and characteristics of products

Summary A study has been made of the relation between processing conditions and the chemical characteristics of cottonseed meals and oils produced by prepressing‐solvent extraction. Twenty‐six complete sets of mill samples of known processing history and representative of the production at 11 mills were used in the investigation. Cooking conditions were the major factor influencing the distribution of the gossypol between the meal and oil. Reduction in free gossypol during cooking was due to binding with meal components while that occurring during prepressing and solvent extraction resulted mainly from removal of gossypol in the prepressed and solvent‐extracted oils. Nitrogen solubility data, which have been suggested as a measure of protein damage, indicated that the major change or reduction in nitrogen solubility occurred during cooking. Very little reduction was noted for prepressing or solvent extraction. The reduction in nitrogen solubility during prepressing is much smaller than that previously reported for normal screw‐pressing operations. Prepressed oils gave lower refining losses and lower refined and bleached color than did the solvent‐extracted oils. Bleach color reversion, after storage of crude oils for 30 days at 100°F., was greater for solvent‐extracted than for prepressed oils. A number of meals exhibited the desirable characteristics of low free gossypol content and high nitrogen solubility. Values calculated for chemical indexes of protein quality, as suggested by Lyman and associates (11), indicate that many of the meals should have good protein quality.