DIGESTIBILITY AND PROTEIN QUALITY EVALUATION OF RAPESEED FLOUR

Flour was prepared from ''Echo'' (Brassica campestris, low erucic acid) and ''Tower'' (B. napus, low erucic acid and low glucosinolate) cultivars of rapeseed by dehulling, myrosinase inactivation, washing in water and hexane extraction. Over 97% of the original glucosinolates were removed. The flours contained over 60% protein. In protein quality tests with weanling rats, those fed rapeseed flour (cv. Echo) grew more slowly than the casein controls. Covariance analysis indicated that these differences could be associated with differences in feed intake or acceptability of the diet. Protein efficiency ratios [PER] were similar for rapeseed flour and casein (3.45 and 3.37, respectively). Tests with weanling mice involving rapeseed flour (cv. Echo) compared with soybean meal, in diets containing 8, 12 and 16% protein, revealed that rapeseed flour was superior to soybean meal as a protein source and had higher digestibility of protein and energy. In a similar test with ''Tower'' flour, protein quality ratings and digestibility coefficients again were superior to those for soybean meal. Rapeseed flour of either cultivar contains highly digestible protein (85-90%) and energy (88-91%). It contains protein equal to casein and superior to soybean protein in terms of PER and biological value. Both flours showed tendencies to be slightly less palatable than the control protein sources.