Effect of the desolventizing/toasting process on chemical composition and protein quality of rapeseed meal

Background： During processing in a desolventizer/toaster（DT）, rapeseed meal（RSM） is heated to evaporate the hexane and to reduce the level of heat-labile anti-nutritional factors such as glucosinolates（GSL）. However, excessive heat treatment may reduce amino acid（AA） content in addition to lower AA digestibility and availability in RSM. The objective of the present study was to produce from one batch of a 00-rapeseed variety（17 μmol GSL/g dry matter（DM）, seed grade quality） five differently processed RSM under standardized and defined conditions in a pilot plant,and to determine the impact of these different treatments on protein solubility and chemical composition, in particular with regard to contents of AA including reactive Lys（rL ys） and levels of total and individual GSL.Methods： Four RSM were exposed to wet toasting conditions（WetT C） with increasing residence time in the DT of 48,64, 76, and 93 min. A blend of these four RSM was further processed, starting with saturated steam processing（〈 100 °C）and followed by exposure to dry toasting conditions（DryT C） to further reduce the GSL content in this RSM.Results： The contents of neutral detergent fiber and neutral detergent fiber bound crude protein（CP） increased linearly（P 〈 0.05）, as residence time of RSM in the DT increased from 48 to 93 min, whereas contents of total and most individual GSL and those of Lys, rL ys, Cys, and the calculated ratio of Lys：CP and r Lys：CP decreased linearly（P ≤ 0.05）.The combination of wet heating and DryT C resulted in the lowest GSL content compared to RSM produced under WetT C, but was associated with lowest protein solubility.Conclusions： It can be concluded that by increasing residence time in the DT or using alternative processing conditions such as wet heating combined with DryT C, contents of total and individual GSL in RSM can be substantially reduced.Further in vivo studies are warranted to elucidate if and to which extent the observed differences in protein quality and GSL content between RSM may affect digestibility and bioavailability of AA in monogastric animals.

Methodological impact of starch determination on starch content and ileal digestibility of starch in grain legumes for growing pigs

Background： Grain legumes represent a valuable energy source in pig diets due to their high starch content. The present study was conducted to determine the content and apparent ileal digestibility（AID） of starch in different grain legume cultivars for pigs by means of both a polarimetric and enzymatic method for starch determination.Methods： Three experiments were conducted with six barrows each which were fitted with ileal T-cannulas. In total, 18 diets including six different cultivars of faba beans（Vicia faba L.） and peas（Pisum sativum L.）, five different cultivars of lupins（Lupinus luteus L., Lupinus angustifolius L.）, and one diet with a soybean meal（SBM） were fed.Results： The starch content of faba beans and peas was greater（P ＆lt; 0.05） when determined polarimetrically than enzymatically（438 vs. 345 g/kg dry matter（DM） in faba beans and 509 vs. 390 g/kg DM in peas, respectively）.Considerable lower starch contents were obtained in lupins and SBM, with 82 and 48 g/kg DM（analyzed polarimetrically） and ＆lt;1.1 and 3 g/kg DM（analyzed enzymatically）, respectively. Mean values for contents of neutral detergent fiber（NDF） and acid detergent fiber（ADF） in grain legumes ranged from 111 and 79 g/kg DM in peas to248 and 207 g/kg DM in lupins, respectively. Contents of condensed tannins in the colored flowered faba bean cultivars ranged from 2.1 to 7.4 g/kg DM. The AID of starch was greater（P ＆lt; 0.05） in pea than in faba bean cultivars,and using the polarimetric starch determination method resulted in greater（P ＆lt; 0.05） digestibility values than using enzymatic starch analysis（84 vs. 80% in faba beans and 86 vs. 83% in peas）. Moreover, AID of starch differed（P ＆lt; 0.05）within pea cultivars and starch digestibility in faba beans decreased linearly（P ＆lt; 0.05） as the content of condensed tannins increased. However, there was no relationship between contents of NDF and ADF and AID of starch in pea and faba bean cultivars.Conclusion： Both contents and AID of starch in grain legumes can vary as influenced by the analytical method used for starch determination. Generally, starch digestibility is greater when measured by polarimetric rather than enzymatic methods.