EFFECTS OF VARIOUS HEAT AND MOISTURE TREATMENTS ON MYROSINASE ACTIVITY AND NUTRITIVE VALUE OF SOLVENT-EXTRACTED CRAMBE SEED MEAL

Abstract

Solvent-extracted crambe meal, uncooked, dry-heated, autoclaved or steam-stripped, was fed as 0, 5 or 10% of the diet to weanling mice. Ground rapeseed (1% of the diet) was fed in a cross-treatment as a source of myrosinase.Uncooked crambe meal significantly depressed (P < 0.05) feed intakes and gains. Heating by any method tested resulted in significant improvement, but feeding value remained below that of the casein-soybean protein control diet. The addition of the myrosinase source had little effect.In a second experiment, ground seed of crambe, rape and camelina (Crambe abyssinica Hochst., Brassica napus L. and Camelina sativa Crantz) were compared as myrosinase sources when incorporated 1:4 into cooked crambe meal and allowed to react overnight at room temperature with 0 or 30% moisture in the mixture. After this enzyme treatment, half of each mixture was autoclaved to destroy myrosinase prior to ration mixing and feeding.Appreciable hydrolysis of thioglucosides occurred in vitro at 30% moisture, resulting in marked growth depression. The feeding of active myrosinase similarly depressed animal responses, apparently through in vivo thioglucoside hydrolysis. All sources of enzyme were effective.The failure to obtain more enzyme response in the first experiment was attributed to lower enzyme concentration and inferior enzyme-substrate proximity during the time when conditions were otherwise appropriate for thioglucoside hydrolysis.