Extraction of β‐Glucan from Oats for Soluble Dietary Fiber Quality Analysis

Abstract

Extraction protocols for β‐glucan from oat flour were tested to determine optimal conditions for β‐glucan quality testing, which included extractability and molecular weight. We found mass yields of β‐glucan were constant at all temperatures, pH values, and flour‐to‐water ratios, as long as sufficient time and enough repeat extractions were performed and no hydrolytic enzymes were present. Extracts contained about 30–60% β‐glucan, with lower proportions associated with higher extraction temperatures in which more starch and protein were extracted. All commercial starch hydrolytic enzymes tested, even those that are considered homogenous, degraded β‐glucan apparent molecular weight as evaluated by size‐exclusion chromatography. Higher concentration β‐glucan solutions could be prepared by controlling the flour‐to‐water ratio in extractions. Eight grams of flour per 50 mL of water generated the highest native β‐glucan concentrations. Routine extractions contained 2 g of enzyme‐inactivated flour in 50 mL of water with 5mM sodium azide (as an antimicrobial), which were stirred overnight, centrifuged, and the supernatant boiled for 10 min. The polymer extracted had a molecular weight of about 2 million and was stable at room temperature for at least a month.

Barley genotypic β-glucan variation combined with enzymatic modifications direct its potential as a natural ingredient in a high fiber extract

“…In addition to peaks eluting in the order T > TA > TAF due to decreasing M w , the polydispersity index (M w /M n ) increased in the order T < TA < TAF, indicating a broadening of the molecular mass distribution in the samples as a result of intensified enzymatic treatment. In a similar study Doehlert et al (2012) found starch hydrolytic enzymes to have a large effect on the M w and polydispersity when used for maximizing the extractability of oat BGs. Hence, efficient BG extractability and recovery must be balanced against M w loss of the extracted BG when using existing enzyme preparations.…”

“…However, introducing more enzymes to a process increases the risk of hydrolytic side-, or contaminating activities on BGs. Few studies using enzymes as part of their BG isolation have investigated, if the amylolytic enzymes had any effect on the BG itself (Benito-Roman et al, 2014;Doehlert et al, 2012). In the present study we screen widely different barley genotypes for BG extraction yields.…”

“…Benito-Román et al (2011) found BG extraction yields of ~73% and ~62% for hulled and hulless barley, respectively. Amylolytic enzymes are widely used for the degradation of starch in BG extraction (Benito-Roman et al, 2014;Doehlert et al, 2012). Following thermal gelatinization the starch is hydrolyzed into maltooligosaccharides, maltose and glucose by the action of endo-and exo-glucanases such as αand β-amylases, glucoamylase and debranching pullulanase.…”

“…This effect could either be due to contaminating activities in the commercial enzyme preparations or due to amylolytic enzymes themselves exhibiting nonspecific activities toward the BG (Doehlert et al, 2012). The degree of BG degradation followed the order T < TA < TAF, and a profound reduction in M w was especially found for the TAF combination, where α-amylase is combined with Fig.…”