Effect of ingestion of dark chocolates with similar lipid composition and different cocoa content on antioxidant and lipid status in healthy humans

The association between in vitro antioxidant capacity of dark chocolates with different cocoa percentage and the in vivo response on antioxidant status was investigated. In a randomized crossover design, 15 healthy volunteer consumed 100 g of high antioxidants dark chocolate (HADC) or dark chocolate (DC). In vitro, HADC displayed a higher Total Antioxidant Capacity (TAC) than DC. In vivo, plasma TAC significantly peaked 2 h after ingestion of both chocolates. TAC levels went back to zero 5 h after DC ingestion whilst levels remained significantly higher for HADC. HADC induced a significantly higher urinary TAC in the 5-12 h interval time than DC. No change was detected in urinary excretion of F2-isoprostanes. Plasma thiols and triacylglycerol (TG) levels significantly increased for both chocolate with a peak at 2 h remaining significantly higher for DC after 5 h respect to HADC. Results provide evidence of a direct association between antioxidant content of chocolate and the extent of in vivo response on plasma antioxidant capacity. (C) 2011 Elsevier Ltd. All rights reserved

Isolation and characterization of water-extractable arabinoxylan from hull-less barley flours

A new procedure was developed for the isolation of highly purified water-extractable arabinoxylan (WE-AX) from hull-less barley flour. It included inactivation of endogenous enzymes, removal of proteins with silica gel, and removing beta-glucans, arabinogalactan-peptides, and starch fragments by enzyme or solvent precipitation steps. WE-AX recovered by this isolation procedure represented, on average, 47% of all WE-AX present in hull-less barley flour. Purified WE-AX from flour of different hull-less European barley cultivars contained 84.9-91.8% AX and showed small structural differences. The apparent peak molecular weight of the purified WE-AX was 730,000-250,000, and the arabinose-to-xylose ratio was 0.55-0.63. Proton nuclear magnetic resonance spectroscopy showed that the levels of un-, O-2 mono-, O-3 mono-, and O-2,O-3 disubstituted xylose residues were 59.1-64.7%, 8.2-10.0%, 5.7-10.6%, and 17.6-23.1%, respectively, and the ratio of di- to monosubstituted xylose was 0.90-1.54. Both O-3 mono- and disubstituted xylose residues occurred isolated or next to disubstituted xylose residues in the WE-AX chain.status: publishe

Enzymic degradability of hull-less barley flour alkali-solubilized arabinoxylan fractions by endoxylanases

The impacts of the arabinose to xylose (A/X) ratio of arabinoxylans (AX) and the endoxylanase substrate specificity on the enzymic degradability of hull-less barley flour AX by endoxylanases were studied by using alkali-solubilized AX (AS-AX) fractions with different A/X ratio, on the one hand, and glycoside hydrolase family 10 and 11 endoxylanases of Aspergillus aculeatus (XAA) and Bacillus subtilis (XBS), respectively, on the other hand. AS-AX were obtained by saturated barium hydroxide treatment of hull-less barley flour water-unextractable AX. Fractionation of AS-AX by stepwise ethanol precipitation resulted in structurally different hull-less barley flour AS-AX fractions. Their A/X ratios increased with increasing ethanol concentration, and this increase in A/X ratio was reflected in their xylose substitution levels. For both XAA and XBS, the enzymic degradability of AX and apparent specific endoxylanase activity decreased with increasing A/X ratio of the AS-AX substrates, implying that both endoxylanases were sterically hindered by arabinose substituents. However, for all AS-AX fractions, hydrolysis end products of lower average degree of polymerization were obtained after incubation with XAA than with XBS, indicating that the former enzyme has a lower substrate specificity toward hull-less barley flour AS-AX than the latter. In addition, apparent specific endoxylanase activities indicated that XBS was similar to 2 times more sensitive to variations in the A/X ratio of AS-AX fractions than XAA. Furthermore, AS-AX with higher A/X ratio were relatively resistant to degradation by XBS.status: publishe

Proteolytic enzymes in germinating rye grains

The proteolytic activities during rye (Secale cereale L. 'Humbolt') grain germination were monitored using in-solution methods and one- and two-dimensional PAGE with gels that contained incorporated substrate proteins. The total proteolytic activity increased during the first three days of germination, but not after that. The proteinase activity was measured at pH 3.8, 6.0, and 8.0 in the presence and absence of class-specific proteinase inhibitors. This indicated that enzymes from all four proteinase classes were present during the germination process. Germinated rye grain contained mainly aspartic and cysteine proteinase activities that are especially active at pH 3.8. Serine- and metallo-proteinases were less abundant. Overall, the pattern of hydrolysis was very similar to that observed during barley and wheat germination.status: publishe

Impact of inhibition sensitivity on endoxylanase functionality in wheat flour breadmaking

A Bacillus subtilis endoxylanase (XBSi) sensitive to inhibition by Triticum aestivum L. endoxylanase inhibitor (TAXI) and a mutant thereof (XBSni), uninhibited by TAXI, were used in straight-dough breadmaking to assess the importance of endoxylanase inhibition sensitivity on endoxylanase functionality in the process. With two European wheat flours, the loaf volume improving effect of XBSni at much lower enzyme dosages was substantially larger than that brought about by XBSi. This coincided with differences in arabinoxylan (AX) hydrolysis. Although XBSni had a lower substrate selectivity for water-unextractable arabinoxylan (WU-AX) than XBSi, the former solubilized significantly more WU-AX than XBSi. Because of inhibition, XBSi solubilized most of the WU-AX during mixing, whereas, with XBSni, the rate of solubilization decreased less with increasing processing time than that with XBSi. During fermentation and baking and at the highest dosage (600 U/kg of flour of XBSi and 60 U/kg of flour of XBSni), XBSni induced a stronger degradation of enzymically solubilized and water-extractable AX than XBSi. Taken together, the data clearly demonstrate that endoxylanases, which in vitro are inhibited by endoxylanase inhibitors and still are active in the breadmaking process, as demonstrated by their functional (bread volume) enhancing effect, gradually lose their activity in the process.status: publishe

The combined use of hull-less barley flour and xylanase as a strategy for wheat/hull-less barley flour breads with increased arabinoxylan and (1 -> 3,1 -> 4)-beta-D-glucan levels

Bread-making with a composite flour (CF) consisting of 60% wheat flour (WF) and 40% hull-less barley flour, increased the total and soluble (1-->3,1-->4)-beta-D-glucan and total arabinoxylan (AX) contents of dough and bread samples, but decreased the specific bread loaf volume. A xylanase insensitive to inhibition by Triticum aestivum L. xylanase inhibitor (TAXI) and xylanase inhibiting protein (XIP), increased loaf volume by 8.8 and 20.1 % for WF and CF breads, respectively. Xylanase addition not only markedly improved loaf volume of CF bread, but also increased the soluble AX content of the WF and CF dough and bread samples because of conversion of water-unextractable AX into soluble AX. The xylanase had no impact on the extractability and molecular weight of (1-->3,1-->4)- beta-D-glucan, but (1-->3,1-->4)-beta-D-glucan was degraded during bread-making probably because of endogenous beta-glucanase activity. Taken together, the results clearly show that the combined use of hull-less barley flour and a xylanase active during bread making, lead to palatable breads with high total and soluble AX and (1-->3,1-->4)-beta-D-glucan contents. The sum of total AX and (1-->3,1-->4)-beta-D-glucan was 1.70% for WF bread and 3.06% for CF bread, while the sum of soluble AX and (1-->3,1-->4)-beta-D-glucan was 0.49 and 1.41% for control WF and CF xylanase supplemented breads, respectively. (C) 2004 Elsevier Ltd. All rights reserved.status: publishe

Consumption of breads containing in situ produced arabinoxylan oligosaccharides alters gastrointestinal effects in healthy volunteers

status: publishe

The bread-making functionalities of two Aspergillus niger endoxylanases are strongly dictated by their inhibitor sensitivities

A recent approach based on affinity chromatography with immobilised endoxylanase inhibitors was used to isolate two endoxylanases (EC 3.2.1.8) with different bread-making functionalities from an Aspergillus niger fermentation broth. TAXI (Triticum aestivum endoxylanase inhibitor) affinity chromatography yielded a TAXI- and XIP (endoxylanase inhibiting protein)-sensitive family 11 endoxylanase (24 kDa, pI 3.5) XIP affinity chromatography subsequently yielded a family 10 endoxylanase (36 kDa), only inhibited by XIP. While the first enzyme improves bread volume, the latter enzyme has no effect on bread quality whatsoever. The bread-making positive endoxylanase rather selectively hydrolyses water-unextractable arabinoxylan in an in vitro screening method, still performs/is active during bread-making and produces soluble arabinoxylan of high (> 11.2 x 10(4) Da) and low molecular mass (less than or equal to 11.2 x 10(4) Da). In contrast, the bread-making neutral endoxylanase in the in vitro assay displays a bias for water-extractable arabinoxylan and is immediately and almost completely inhibited during the early stages of bread-making. The results show that the functionalities of the purified A. niger endoxylanases in wheat bread-making are strongly dictated by their sensitivities towards wheat endoxylanase inhibitors. (C) 2004 Elsevier Inc. All rights reserved.status: publishe

Milling performance of north European hull-less barleys and characterization of resultant millstreams

Four hull-less barley samples were milled on a Buhler MLU 202 laboratory mill and individual and combined milling fractions were characterized. The best milling performance was obtained when the samples were conditioned to 14.3% moisture. Yields were 37-48% for straight-run flour, 47-56% for shorts, and 5-8% for bran. The beta-glucan contents of the straight-run white flours were 1.6-2.1%, of which approximate to49% was water-extractable. The arabinoxylan contents were 1.2-1.5%, of which approximate to17% was water-extractable. Shorts and bran fractions contained more beta-glucan (4.2-5.8% and 3.0-4.7%, respectively) and arabinoxylan (6.1-7.7% and 8.1-11.8%, respectively) than the white flours. For those fractions, beta-glucan extractability was high (58.5 and 52.3%, respectively), whereas arabinoxylan extractability was very low (approximate to6.5 and 2.0%, respectively). The straight-run white flours had low alpha-amylase, beta-glucanase, and endoxylanase activities. The highest alpha-amylase activity was found in the shorts fractions and the highest beta-glucanase and endoxylanase activities were generally found in the bran fractions. Endoxylanase inhibitor activities were low in the white flours and highest in the shorts fractions. High flavanoid, tocopherol, and tocotrienol contents were found in bran and shorts fractions.status: publishe

Consumption of Breads Containing In Situ-Produced Arabinoxylan Oligosaccharides Alters Gastrointestinal Effects in Healthy Volunteers

Arabinoxylan oligosaccharides (AXOS) are studied as food compounds with prebiotic potential. Here, the impact of consumption of breads with in situ-produced AXOS on intestinal fermentation and overall gastrointestinal characteristics was evaluated in a completely randomized, double-blind, controlled, cross-over study. Twenty-seven healthy volunteers consumed 180 g of wheat/rye bread with or without in situ-produced AXOS (WR+ and WR-, respectively) daily for 3 wk. Consumption of WR+ corresponded to an AXOS intake of similar to 2.14 g/d. Refined wheat flour bread without AXOS (WT) (180 g/d) was provided during the 3-wk run-in and wash-out periods. At the end of each treatment period, participants collected urine for 48 h as well as a feces sample. Additionally, all participants completed a questionnaire about stool characteristics and gastrointestinal symptoms during the last week of each period. Urinary phenol and p-cresol excretions were significantly lower after WR+ intake compared to WR-. Consumption of WR+ significantly increased fecal total SCFA concentrations compared to intake of W-. The effect of WR+ intake was most pronounced on butyrate, with levels 70% higher than after consumption of W- in the run-in or wash-out period. Consumption of WR+ tended to selectively increase the fecal levels of bifidobacteria (P = 0.06) relative to consumption of W-. Stool frequency increased significantly after intake of WR+ compared to WR-. In conclusion, consumption of breads with in situ-produced AXOS may favorably modulate intestinal fermentation and overall gastrointestinal properties in healthy humans. J. Nutr. 142: 470-477, 2012