Abstract
Effects of heating cottonseed meal (CSM) protein were quantitatively assessed by determination of true digestibility (TD), in vitro proteolysis, N solubility and fluorodinitrobenzene (FDNB) available lysine. Flaked, dehulled cottonseed was extracted with hexane and desolventized at 25 C, then autoclaved (121 C, 1.1 kg/cm(2)) for 0, 15, 30, 60, 90 or 120 minutes. Free gossypol was subsequently extracted, and TD was determined in weanling rats. Metabolic fecal N (the fecal N excreted by rats fed a basal diet containing 4% casein protein) was 1.84 +/- .10 mg N/g dry matter intake. TD and FDNB-available lysine (percentage of total) were 91 and 89%, respectively, in the unheated meal. TD and FDNB-available lysine were reduced to 84 and 78% after 60 min of autoclaving, and to 71 and 44% after 120 min of autoclaving. The effect of heat treatment on TD was described by the equation: % TD = 100 - 9.28e(.0096t) (r = .998), where t = minutes of autoclaving. This indicated an accelerated decline in TD as heating time increased. No more than 40% of the loss in FDNB-available lysine was attributable to gossypol binding. In vitro release of total amino acids from autoclaved CSM samples during pepsin-pancreatin incubations was highly correlated to TD (r = .996), but N solubility in .02 N NaOH was poorly correlated to TD. In samples of solvent-extracted and screw-pressed CSM, TD (estimated from pepsin-pancreatin incubations) ranged from 80 to 85% and FDNB-available lysine ranged from 73 to 85%, and both were only slightly lower in screw-pressed than in solvent-extracted meals. Intake of FDNB-available lysine was correlated (r = .902) to weight gain in rats fed diets containing the CSM that were more severely autoclaved. Results suggest that heat treatment must be more severe than that which normally occurs in commercial CSM processing to cause substantial, selective loss in lysine availability.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
