Aqueous extracts of rapeseed meals were separated into four fractions by Sephadex (G25) column chromatography. Fraction I was found to be rich in protein as judged by nitrogen and amino-acid content and U.V. absorbance at 280 nm. Fraction I1 contained glucosinolates and peptide-like materials. Fractions I11 and IV contained only trace amounts of amino acids and nitrogen. Further separation of fraction IV into three components was achieved by chromatography on silicic acid. Two of the components were shown, by paper chromatography and U.V. absorbance scanning, to be rich in caffeic acid and chlorogenic acid, respectively.
Protein concentrates have been prepared from rapeseed meals by extraction with sodium chloride solution, followed by removal of the seed coat by screen filtration. This method yielded up to 75% of the original meal N in the form of products containing 61-64 % protein ( N x 6 . 2 5 ) . The products showed a considerably greater content of ash, and lower content of crude fibre and glucosinolate than did the starting meals, but amino acid patterns were similar and P levels were unchanged. Protein quality of the products prepared from heat-treated (myrosinase-inactivated) meals, was measured by determination of protein efficiency ratio and net protein utilisation, and was found to be similar to that of casein.
Rapeseed meals were prepared from B. napus rapeseed, either from seed previously heated in boiling water for 10 min or from unheated seed. Rats were dosed by stomach tube with 1 g of each meal and urine was collected for periods of 8,16, 24, and 36 h. Representative rats were sacrificed at these times and total gastrointestinal contents plus feces and total blood were collected. All samples, including the meals, were subjected to analyses for isothiocyanates, nitriles (BCN), and goitrin (OZT), both with and without myrosinase treatment. Significant amounts of glucosinolates were absorbed and excreted intact in the urine. The heated meal yielded more BCN and OZT in the urine than did the raw meal. At 8 h considerable amounts of OZT were found in the blood of rats dosed with heated meal. No free isothiocyanates were found in any of the samples examined. However, following dosing with heated meal, urine treated with myrosinase yielded isothiocyanates equivalent to 40% of their parent glucosinolates present in the meal. Evidence suggests that when heated or raw meals are ingested the main toxic substances formed are BCN and OZT, the former predominating in the case of raw meal and the latter in the case of heated meal.
The glucosinolate form of 3-butenyl isothio-low iodine diets. Growth depression occurred cyanate (BNCS)G was compared in two ex-with dietary (BNCS)G levels of 2-? ^ele periments with rapeseed meal (RSM) gluco-diet. Less than half this amount of BNCS sinolates (including oxazolidinethione, (BNCS) gave similar effects. Thyroid enlargement was G, and (OZT)G), and with the hydroiyzed greatest when (OZT)G was fed. The glucocompounds 3-butenyl isothiocyanate (BNCS) sinolate (BNCS)G resulted in reduced proand 3-butenyl cyanide (BCN) combined. portions of triiodothyronine (*I-T") and thyThese were fed to rats for 21 days.
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