Effects Of Wheat Bran Insoluble Dietary Fiber On Dry White Noodles

Laboratory-made wheat bran insoluble dietary fiber(IDF)was sieved after ultrafine grinding as a source of dietary fiber,dry white Chinese noodles was chosen as the IDF carrier to study the effects of wheat bran IDF on dry white noodles.Different proportion and particle size of IDF caused the wide-ranging effects of noodles such as noodle color,texture characteristics,sensory evaluation,moisture distribution,amount of hydrosulphonyl and disulfide Bond,secondary structures of proteins.Combined with correlation analysis and principal component analysis,the mechanism of wheat bran IDF on noodle quality impacts was discussed.The main findings are as follows:(1)The high content and large particle size of IDF caused L*to fall and b*increase,even L*variation of noodles was slightly restrained after cooking.The discriminating contents of IDF drove TPA values first increased and then decreased,the tensile strength decreased after increasing,and the maximum shear force kept increasing continually.As IDF particle size changed,TPA values,maximum shear force and tensile strength all emerged to rise after declining.Correlation analysis showed that the sensory score,L*and tensile strength positively correlated,while b*negatively correlated.The dilution of gluten,destruction of IDF crystal structure by ultrafine grinding,exposure of active groups and particles disturbing of gluten network or other macromolecules may be the main causes for quality changes of noodles with IDF.(2)T21 and T22 decreased as IDF content increased.Smaller IDF particle caused T21 decreased first and then increased,while T22 continued to decline.SEM observation showed that the sample T21 changed mainly due to the scatter and dilution effect of gluten network caused by IDF.Correlation analysis showed a positive correlation with T21,L*and the sensory score.Though IDF urged moisture to combine more tightly,strong crush destroyed the crystal structure,the internal network and the chains integrity reduced the water retention ability of IDF.(3)By the addition of IDF,-SH content increased,-SS-content decreased.With smaller IDF particle coexisted,-SH content increases,-SS-content decreases and gradually stabilized.The correlation coefficient of-SS-amount and IDF content was-0.981,and that of-SS-amount and IDF particle size was 0.953.This phenomena can be explained as disulfide bond breaking in protein which influenced by the binding of phenolic acids in pentosan and protein,and the crosslinking between IDF hydrophilic groups and starch.(4)The increasing of effective contact areas,active group of IDF and the transformation between ? and ? or in?1,t and r of protein may be the main reasons for the secondary structure changes as IDF added to noodles.Correlation analysis Partial confirmed the possibility of secondary structure transformation.(5)The correlation between noodle quality and structure showed that:As the amount of IDF varied,L*and b*was significantly associated with most of the structural parameters.Noodle hardness and chewiness were both significantly positively correlated to r structure of protein.Maximum shear force had a significant positive correlation with the-SH content and a significant negative correlation with-SS-.Significantly positively correlation was also foud between T21 and(?+?).On the other hand,with the particle size of IDF varied,Highly significant correlation was found among L*,b*and-SH content.The tensile strength of noodles and secondary structure content of protein were significantly correlated.T21 had significantly negatively correlation with astructure,while T22 had a wide association with all five kinds of secondary structure of protein.(6)Principal component analysis of the parameters were divided into three main components(3 groups)F1?F3.F1 indicated noodles TPA test features,to which internal changes in protein secondary structure was strong related.F2 could be explained as the overall steady-state of macromolecule spatial structure and associated closely with noodle color.F3 refered to sensory characteristics of noodles that closely tied to the containing of water in gluten network and retention of water of macromolecules such as starch and IDF.Therefore,the changes of noodle qualities that caused by wheat bran IDF was mainly due to the transformation of protein secondary structure content,the overall structural stability of gluten network and starch crystal and the distribution of water in noodles.