| During flour processing,a large amount of free radicals can be produced during the catalysis of linoleic acid by lipoxygenase(LOX),resulting in protein polymerization and the conversion of free sulfhydryls to disulfide bonds.Consequently,the gluten protein thews are enhanced.Meanwhile,LOX can improve the flour color through damaging the double bond structure of carotenoids by coupling reaction.Due to the dual roles of LOX,it has been applied in wheat flour and flour products in the last decade.On the other hand,the studies about recombinant lipoxygenase are increasing continuously,due to its advantages,including high enzyme purity,low cost and high efficiency.As a novel type of green flour improver,recombinant lipoxygenase has a huge market demand up to now,the feasibility of improving flour quality by means of enzymes,such as glucose oxidase and laccase has been explored.However,few studies about the effect of recombinant lipoxygenase on the interaction between arabinoxylan and gluten protein has been reported.This paper aimed at studying the influence of recombinant lipoxygenase on the interaction between water-soluble arabinoxylan and gluten protein,as well as investigating the effect of recombinant lipoxygenase and water-soluble xylan addition on dough rheology properties and bread quality.All the results can provide guidance for developing green flour enzymatic modifiers.The main results are shown as follows:1.Extraction and purification of water-extractable arabinoxylan in wheat.Wheat bran Yangmai 15 was used as experimental materials,and crude polysaccharide was obtained by water extraction and alcohol precipitation.Then WEAX was further purified by DEAE-cellulose ion column chromatography and Sephdex G-100 column chromatography.After that,the composition and molecular weight of the extract was analyzed.The results indicated that the extraction yield of WEAX was 1.04%.The contents of total sugar,protein,and pentosan content in the extract were 93.57%,3.53%and 89.68%,respectively.Furthermore,the extract obtained by stated method had high purity.The relative molecular weight of WEAX was 398107 on average.Monosaccharide composition analysis showed that it was mainly composed of 46.57%Arabia,51.43%xylose,0.73%glucose and 1.27%mannose.In addition,the content of FA(Ferulic acid),which played an important role on the oxidation crosslinking and functional properties of WEAX was 4.36 mg/g.2.Effect of recombinant lipoxygenase on water-soluble arabinxylan oxidation crosslinking.Through the determination of viscosity,particle size,critical association concentration,molecular weight and ferulic acid content,as well as infrared spectrum analysis,it was found that when the amounts of Ana-rLOX and LA added were 72 IU/mg and 0.210mg/mg,the particle size of WEAX solution catalyzed by Ana-rLOX increased significantly.The viscosity of WEAX solution was 21.75 mPa·s,while its viscosity increased to approximately 48.93 mPa·s after the addition of Ana rLOX.The critical association concentration of WEAX solution decreased from 0.58 mg/mL to 0.42 mg/mL after catalysis of Ana rLOX.Moreover,enzymatic catalysis led to the enhancement of WEAX molecular weight.The FA content in WEAX was reduced greatly,demonstrating the important role of FA on WEAX oxidation crosslinking.The EPR spin trapping technique was used for detecting free radical signals generated during the catalysis of LA by Ana-rLOX.The results revealed that the intensity of free radical decreased after the addition of FA,indicating that FA was directly involved in the oxidative crosslinking,and WEAX can be oxidized and cross-linked by FA in the presence of Ana-rLOX.3 Effect of recombinant lipoxygenase on the interaction between water-soluble arabiaxylan and gluten protein.Through determining free sulfhydryl content,surface hydrophobicity and size,as well as utilization of intrinsic fluorescence spectroscopy and infrared spectroscopy analysis,the effect of Ana-rLOX on the interaction between WEAX and gluten protein were studied.The results showed that the free sulfhydryl content of the sample added with both WEAX and Ana-rLOX decreased from 13.7 mol/g to 9.3 mol/g,which was 21.1%lower than that of sample added with WEAX alone.In the meantime,the surface hydrophobicity enhanced remarkably.The particle size of gluten protein added with Ana-LOX and WEAX increased to 224.7 nm.Moreover,the results about infrared spectrum revealed that the absorption peaks of wheat gluten containing WEAX and Ana-rLOX changed.Specifically,the hydrogen bond between wheat protein moleculers enhanced significantly.The elastic modulus and viscous modulus of the sample added with Ana-rLOX and WEAX increased significantly.In smummary,Ana-rLOX could promote the interaction between WEAX and WG.4.Effect of recombinant lipoxygenase on dough rheological properties and bread staling.The results showed that bread specific volume increased by 11.6%after the addition of WEAX alone.Meanwhile,bread specific volume increased by 13.6%when both Ana-rLOX and WEAX were added.Furthermore,chewiness,hardness,gumminess,resilience and bread overall quality were all improved.In addition,bread antiaging experiments showed that the rates of both bread moisture loss and hardness increase decreased after the addition of Ana-rLOX and WEAX.All these results indicated that WEAX crosslink catalyzed by Ana-rLOX can delay the aging of bread. |
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