title: Content and molecular weight of water-extractable arabinoxylans in wheat malt and wheat malt-based wort with different Kolbach indices.
abstract: BACKGROUND
  Arabinoxylans (AXs) are partially water-extractable polymers that cause problems of viscosity and filterability during beer brewing. This study investigated the effects of Kolbach index (KI) on water-extractable AXs (WEAXs).
  
  
  RESULTS
  KI had positive correlations with extract (r = 0.845) and free amino nitrogen (FAN) (r = 0.958). The contents of malt WEAXs (WEAXsm), total AXs and wort AXs (WAXs) were 10.8-11.6 g kg⁻¹, 57.5-60.8 g kg⁻¹ and 137.5-140.5 mg per 100 mL respectively and the corresponding arabinose/xylose (A/X) ratios were 0.52-0.56, 0.55-0.62 and 0.48-0.50. The molecular weight (Mw) ranged from 4.92 × 10⁴ to 6.93 × 10⁴ Da for WEAXsm and from 1.24 × 10⁴ to 2.90 × 10⁴ Da for WAXs. KI had negative correlations with the average degree of polymerization (avDP) of malt (r = -0.877) and wort (r = -0.978). Wort viscosity showed a positive correlation with the Mw of WEAXsm (Mwm) (r = 0.821).
  
  
  CONCLUSIONS
  Increasing KI can promote the degradation of the xylan backbone, while it cannot affect the branching of the polymer chain and the content and Mw of WEAXs.
authors.affiliation: College of Food Science and Engineering, Shandong Agricultural University, Tai'an, Shandong, 271018, China.
authors.forename: Mengmeng
authors.initials: M
authors.lastname: Guo
authors.forename: Jinhua
authors.initials: J
authors.lastname: Du
authors.forename: Kaili
authors.initials: K
authors.lastname: Zhang
authors.forename: Yuhong
authors.initials: Y
authors.lastname: Jin
mesh_terms: D000465:Algorithms; D001089:Arabinose / Q000032:analysis; D001426:Bacterial Proteins / Q000378:metabolism; D055598:Chemical Phenomena; D002681:China; D005511:Food Handling; D063427:Food Quality; D018525:Germination; D006026:Glycoside Hydrolases / Q000378:metabolism; D006868:Hydrolysis; D055595:Mechanical Phenomena; D008970:Molecular Weight; D058105:Polymerization; D012639:Seeds / Q000737:chemistry* / Q000254:growth & development; D012995:Solubility; D014908:Triticum / Q000737:chemistry* / Q000254:growth & development; D014783:Viscosity; D014990:Xylans / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D014994:Xylose / Q000032:analysis; D000516:alpha-Amylases / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D014990:Xylans; C085118:arabinoxylan; D014994:Xylose; D001089:Arabinose; D006026:Glycoside Hydrolases; D000516:alpha-Amylases; C028020:licheninase
keywords: Kolbach index; arabinoxylans; content; molecular weight; wheat malt