Search

During the wet separation of starch and gluten, both water extractable pentosans (WEP) and water unextractable solids (WUS) have a negative effect on gluten yield. Gluten properties are also affected: the gluten becomes less extensible. In comparison to the control, addition of WUS or WEP resulted in less gluten with a higher maximum resistance to extension (Rmax) and a smaller extensibility at maximum resistance (E at Rmax). The corresponding glutenin macropolymer (GMP) gel was more elastic, and the specific volume of the GMP particles was larger and their tendency to aggregate was lower. In contrast, the use of xylanase or ferulic acid (FA) resulted in a higher gluten yield and a larger E at Rmax of gluten. Here, the GMP was characterised by a more viscous gel structure, a smaller specific volume of the GMP particles and a larger tendency of GMP particles to aggregate. Correlations between gluten properties (Rmax, E at Rmax) and GMP particle properties ([η], K′) were observed. Based on these observations, we propose a possible explanation for the effect of pentosans on gluten formation and properties. Both a physical effect and a chemical effect are involved. The physical effect is related to viscosity and likely also to depletion attraction between protein particles. The chemical effect is related to a FA-mediated effect and ‘controls’ the tendency of the particles to aggregate (K′). The contribution of physical and chemical effects leads to a partial agglomeration of GMP particles and shifts the GMP particle size distribution to a higher value. Since GMP particle properties could be directly related to gluten rheological properties, this explains the change in quality observed. [Copyright &y& Elsevier]

In the gluten-starch separation process gluten is formed first as a result of breakdown of the gliadin-glutelin structures during mixing followed by their re-agglomeration. To date the effect of pentosans and enzymes have not been studied separately. A simple modification of TNO Glutomatic system enables pentosans, enzymes, and other materials to be added after the mixing step allowing the effect of these additives to be studied separately. Using this technique, we observed that re-aggregation of gluten proteins starts immediately after the first mixing step during the dough dilution phase. Xylanase addition prior to dough mixing can lead to ‘overdose effects’ but these were not observed when xylanase was added later during the re-agglomeration phase. We were able to distinguish between physical and chemical effects of pentosans on gluten formation. The effect of water-extractable pentosans is only partly related to its viscosity, a ferulic acid (FA) related reaction is more important. Pentosans affect the affect the agglomeration by increasing the size of the glutenin macropolymer particles. When the water-extractable pentosan effect is prevented by xylanase or FA addition, aggregation during dilution is more extensive and the glutenin macropolymer has a lower average particle size with a resulting difference in gluten rheology. [Copyright &y& Elsevier]

Representatives of three types of feruloyl esterases were examined for their ability to release mono- and di-meric ferulic acid from water-extractable and water-unextractable cereal cell wall material, either alone or in the presence of a family 10 or family 11 xylanase. A type-C feruloyl esterase from Talaromyces stipitatus (TsFaeC) released 100% of the ferulic acid from water-extractable wheat endosperm arabinoxylan when acting in combination with a xylanase from Trichoderma longibrachiatum. The type-A esterase from Aspergillus niger, AnFaeA, was most effective in releasing ferulic acid from wheat bran and brewers'' spent grain, with over 50% of the available ferulic acid being released from wheat bran in the presence of a xylanase from Bacillus subtilis. In general, family 11 xylanases were the preferred synergistic partners with feruloyl esterases for the release of ferulic acid, while family 10 xylanases were preferred for the liberation of diferulic acid, with only the 5,5′ form being released by the action of AnFaeA alone. This suggests that ferulic acid may be located in regions of low substitution on arabinoxylans while the 5,5′ diferulate moiety is located in more branched regions of the xylan chain. [Copyright &y& Elsevier]

In a previous study, we have shown that water unextractable solids (WUS) interfere with gluten formation and affect the quality of the resulting gluten. In this study we aim to explain how WUS can affect the process of gluten formation. To this end, WUS were modified with NaOH, xylanase, horseradish peroxidase (HRP) and hydrogen peroxide (H2O2). Effects of modified WUS on gluten yield, dough properties, and gluten and glutenin macropolymer (GMP) composition and properties were studied. The results showed that addition of WUS to wheat flour led to a lower gluten yield and gluten starch yield, a higher Rmax and a lower E at Rmax of gluten and a more concentrated and elastic GMP gel. Pretreatment of WUS by NaOH, xylanase, HRP and H2O2 cannot correct its negative effect on gluten yield, but addition of xylanase or free ferulic acid (FA) during gluten separation can remove or prevent the negative effect of WUS on gluten yield. Compared to addition of only WUS, addition of WUS and FA together to wheat flour resulted in a higher gluten yield, a higher E at Rmax of gluten, and a less concentrated and elastic GMP gel. Similar to water extractable pentosans (WEP), FA bound WUS plays a key role in the effect of WUS on gluten yield and properties. It appears that there is a common mechanism regarding the effect of WUS and WEP that the oxidative cross-linking during gluten formation could be prevented by FA addition. The difference between both is that WUS have a higher water binding capacity, which is reflected in a higher Rmax of dough and gluten in the presence of WUS. [Copyright &y& Elsevier]

An extracellular feruloyl esterase (FAE-II) from the culture filtrates of Fusarium oxysporum F3 was purified to homogeneity by SP-Sepharose, t-butyl-HIC and Sephacryl S-200 column chromatography. The protein corresponded to molecular mass and pI values of 27 kDa and 9.9, respectively. The enzyme was optimally active at pH 7 and 45 °C. The purified esterase was fully stable at pH 7.0–9.0 and temperature up to 45 °C after 1 h incubation. Determination of kcat/Km revealed that the enzyme hydrolysed methyl sinapinate 6, 21 and 40 times more efficiently than methyl ferulate, methyl coumarate and methyl caffeate, respectively. The enzyme was active on substrates containing ferulic acid ester linked to the C-5 but inactive to the C-2 positions of arabinofuranose such as 4-nitrophenyl 5-O-trans-feruloyl-α-l-arabinofuranoside and 4-nitrophenyl 2-O-trans-feruloyl-α-l-arabinofuranoside. In the presence of Sporotrichum thermophile xylanase, there was a significant release of ferulic acid from destarched wheat bran by FAE-II, indicating a synergistic interaction between FAE-II and S. thermophile xylanase. FAE-II by itself could release only little ferulic acid from destarched wheat bran. The potential of FAE-II for the synthesis of various phenolic acid esters was tested using as a reaction system a surfactantless microemulsion formed in ternary mixture consisting of n-hexane, 1-propanol and water. [Copyright &y& Elsevier]

In our previous study, FA15 (2-methyl-1-butyl ferulic acid) was chemically synthesized as a novel ferulic acid (FA) analog, and found to notably suppress phorbol ester-induced Epstein–Barr virus activation and superoxide anion generation in vitro. In this report, we demonstrated that FA15, in contrast to FA, markedly suppressed the combined lipopolysaccharide and interferon-γ-induced protein expressions of inducible nitric oxide synthase and cyclooxygenase-2, and also inhibited the release of tumor necrosis factor-α accompanied by suppression of I-κB degradation in RAW264.7, a murine macrophage cell line. In ICR mouse skin, topical application of FA15 significantly attenuated phorbol ester-triggered hydrogen peroxide production and edema formation as well as papilloma development while that of FA did not. Our results suggest that FA15, derived from natural sources, is a novel chemopreventive agent, both structurally and functionally. [Copyright &y& Elsevier]