title: Effect of the desolventizing/toasting process on chemical composition and protein quality of rapeseed meal.
abstract: 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 (rLys) and levels of total and individual GSL.
  
  
  METHODS
  Four RSM were exposed to wet toasting conditions (WetTC) 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 (DryTC) 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, rLys, Cys, and the calculated ratio of Lys:CP and rLys:CP decreased linearly (P ≤ 0.05). The combination of wet heating and DryTC resulted in the lowest GSL content compared to RSM produced under WetTC, 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 DryTC, 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.
authors.affiliation: University of Hohenheim, Institute of Animal Science, Emil-Wolff-Strasse 10, Stuttgart, 70599 Germany.
authors.forename: Rainer
authors.initials: R
authors.lastname: Mosenthin
authors.affiliation: University of Hohenheim, Institute of Animal Science, Emil-Wolff-Strasse 10, Stuttgart, 70599 Germany ; Present address: KWS SAAT SE, Grimsehlstrasse 31, Einbeck, 37555 Germany.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Messerschmidt
authors.affiliation: University of Hohenheim, Institute of Animal Science, Emil-Wolff-Strasse 10, Stuttgart, 70599 Germany ; Present address: Landwirtschaftliche Untersuchungs- und Forschungsanstalt Speyer, Obere Langgasse 40, Speyer, 67346 Germany.
authors.forename: Nadja
authors.initials: N
authors.lastname: Sauer
authors.affiliation: OLEAD, 11 rue Monge, Parc Industriel, Pessac, 33600 France.
authors.forename: Patrick
authors.initials: P
authors.lastname: Carré
authors.affiliation: Terres Inovia, 11 rue Monge, Parc Industriel, Pessac, 33600 France.
authors.forename: Alain
authors.initials: A
authors.lastname: Quinsac
authors.affiliation: Thuringian State Institute of Agriculture, Naumburger Strasse 98, Jena, 07743 Germany.
authors.forename: Friedrich
authors.initials: F
authors.lastname: Schöne
keywords: Anti-nutritional factor; Glucosinolate; Processing; Protein quality; Rapeseed meal