ORIGINAL PAPER
Effect of thermal processing on the protein value
of double-low rapeseed products.
2. Effect of processing stages in the oil plant
and of toasting in laboratory conditions
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The Kielanowski Institute of Animal Physiology and Nutrition, Polish Academy of Sciences,
05-110 Jabłonna, Poland
Publication date: 1994-02-21
J. Anim. Feed Sci. 1994;3(1):43-55
KEYWORDS
ABSTRACT
The effects of two main processing stages (cooking and toasting) in extraction plant on the
nutritional value of double-low rapeseed products were studied. Raw seeds and cooked cake taken
from the oil factory were defatted and compared with toasted rapeseed meal in N balance/growth
performance experiment with rats and in growth performance experiment with brolier chickens.
Moreover, the effect of temperature and time of heating in the laboratory (100 and 120°C for 10, 20 or
30 min) on protein value of defatted expeller cake was also studied in N balance/growth perfomance
experiment with rats.
The toasting process had the most depressing effect on the content of total and available lysine
and of glucosinolates as compared to their level in the seeds. The rats and chickens fed with diet
containing toasted rapeseed meal performed better than those fed with diets containing non-heated
defatted rape seeds or cooked and defatted cake. The toasting process reduced harmful effect of rape
seed on (P≤0.01) the thyroid and liver weights of rats and thyroid weight of chickens.
Increasing temperature and time of laboratory heating resulted in linear decrease (P≤0.001) in
lysine, available lysine and glucosinolate contents as well as protein value of defatted cake for rats
(TD, BV and NPU). However, the decrease in lysine content was much more dependent on the
increase of temperature than on the prolongation of heating. The performance of rats (body weight
gain, feed utilization) was influenced (P≤0.01) by both factors. Feed intake and weight gain of rats
decreasd as time of heating increased but only at higher temperature (120°C). The thyroid weight
linearly deceased (P≤0.01) as temperature increased.
It seems that toasting of double-low RSM in mild conditions is necessary to eliminate the negative
infuence of residual glucosinolates on the animal performance.
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