Effects Of Inulin On Moisture Migration In Wheat Dough And Steamed Bread During The Storage

Inulin,as a kind of new resource food ingredients,and its application in food is becoming more and more popular.We can achieve the purpose of improve people's daily diet dietary fiber intake by adding inulin to the flour products.This research studied the effect of three kinds of inulin with different degree of polymerization(DP)and different amounts of addition(0.0%,2.5%,5.0%,and 10%)on the moisture migration behavior in dough using differential scanning calorimetric(DSC)and nuclear magnetic resonance(NMR).And preliminary discussed the effect of inulin on the water migration of steamed bread during the storage time.The results provided a scientific basis for depth of application of inulin in flour products.The main conclusions are as follows.1.The results of DSC showed that inulin with different DP all decreased the freezable water content and increased non-freezable water content in low-protein flour dough and plain flour dough.In which,the effect of long-chain inulin was the most significant.But for the high-protein dough,the addition of three kind of inulin all increased the freezable water content and decreased the content of non-freezable water.At the same time,the results of NMR showed that with the increase of inulin,the content of tightly bound water and free water increased in the low-protein flour dough and plain flour dough,while the loosely bound water content reduced.For the high-protein flour dough,the tightly bound water content decreased and the loosely bound water and free water increased.The addition of three kinds of inulin had obvious impact on the loosely bound water and free water of low-protein flour dough and free water of plain flour dough and tightly bound water of high-protein flour dough,respectively.On the other hand,in the three kind of inulin,the long-chain inulin had the most obvious effect on the relaxation times of loosely bound water and free water.The relaxation times of T22 and T23 had significant reduction when the amount of long-chain inulin higher than 5%(P<0.05).In addition,the results of water state in dough measured by DSC and NMR were consistent.In general,three kinds of inulin all can significantly change the moisture distribution in the dough.2.After fermentation,the water of low protein flour dough and plain flour dough would happen further migration.DSC results shown that with the addition of three kinds of inulin,the ratio of freezable water to non-freezable water of low protein flourfermented dough and plain flour fermented dough decreased.When the increasing addition amount of three kinds of inulin reached to 10%,respectively,the ratio of freezable water to non-freezable water of low protein flour fermented dough and plain flour fermented dough contained short-chain inulin was reduced by 14.93% and20.08%,respectively.The ratio of freezable water to non-freezable water of low protein flour fermented dough and plain flour fermented dough with natural inulin was reduced by 13.90% and 22.19%,respectively,and the ratio of freezable water to non-freezable water of low protein flour fermented dough and plain flour fermented dough with long-chain inulin was reduced by 18.70% and 12.22%,respectively.NMR results showed that inulin with different DP all had little impact on the relaxation times of T21 and T22(P>0.05),while the relaxation times of T23 had significant reduction.During fermentation,with the increasing of three kinds of inulin,the tightly bound water content of low protein flour fermented dough and plain flour fermented dough decreased and the loosely bound water and free water increased.The long-chain inulin had the most obvious effect on the fermented dough.And for the two kinds of fermented dough,the effect of inulin on plain flour fermented dough was more significant.Through the correlation analysis,we can see that the change trend of freezable water content of fermented dough determined by DSC was consistent with the change trend of loosely bound water content and free water content determined by NMR,the change trend of non-freezable water was same to the tightly bound water.3.During the storage time of first three days of low protein steamed bread and plain steamed bread,the total water content and migration rate of freezable loosely bound water increased with the increasing addition amount of three kinds of inulin.But in the later storage time,the water migration rate decreased.At the same time,the weaker interaction of freezable water with starch and protein chains became stronger,while the stronger interaction of tightly bound water with starch and protein chains decreased compared to the control.During the whole storage,three kinds of inulin all accelerate water migration of two kinds of steamed bread with different protein content from the inside to the outside,thus speeding up the staling of steamed bread.