Effect of mild heat treatment on the nutritive value of low glucosinolate–low erucic acid rapeseed meals

Abstract

Abstract Heat treatment (dipping seeds in boiling water) of two cultivars of Brassica napus , 1788 and 940, low in glucosinolates and erucic acid produced improved weight gains and lower thyroid weights in rats who received these meals as the only source of protein. Unheated cv 940 meal on autolysis did not produce detectable amounts of nitriles and increased weight gains were observed in rats ingesting the autolysed meal. Steaming of unheated meal similarly gave increased weight gains and the effects of steaming and autolysis were additive. The rates of weight gain of rats who ingested unheated and heated meals were different for the first ten days of feeding the meals but subsequently were similar, indicating the possibility of palatability factor(s) or another appetite depressing factor(s) being present in unheated meals. Trypsin inhibitor activities determined for various rapeseed meals were low as compared to soybean. Chlorogenic acid and myrosinase, both known constituents of rapeseed, did not show any trypsin inhibitor activity. In vitro digestibility measurements with pancreatin and pepsin didnot show significant differences between heated and unheated meals nor did an in vivo digestibility trial, although the rats consumed less of the feed containing unheated meal.