| In this paper,corn gluten meal was used as the object of study.Corn antioxidant peptides were prepared by enzymatic hydrolysis and two different molecular weight corn peptide powders were prepared by ultrafiltration and freeze-drying.With low field nuclear magnetic resonance(LF-NMR),Nano ZS90 Zeta particle size analyzer,electron paramagnetic resonance spectroscopy(ESR)and circular dichroism technology,corn peptide powder with molecular weight less than 1 k Da and 10~30 k Da molecular weight sample were studied about analysis of the moisture absorption characteristics and effect on its quality.The results of this study are as follows:(1)In the short-term study of moisture absorption,corn antioxidant peptides were prepared from corn gluten meal by enzymolysis,and two corn flour peptides with different molecular weight were prepared by ultrafiltration and freeze-drying.Use LF-NMR technology to study the dynamic moisture migration and distribution of the corn peptide powder with molecular weight less than 1 k Da and 10~30 k Da molecular weight were stored at 25℃ under the condition of low humidity and high humidity in the environment of 35% RH and 80% RH about 8h and try to explain the influence of different molecular weight of peptide powder in the moisture absorption process for the further study of corn antioxidant peptide hygroscopicity and moisture migration.The experimental results show that corn peptide powder of different molecular weight has different moisture absorption characteristics.Under the condition of 25 ℃and 80% RH,the powder of corn antioxidant peptide molecular weight less than 1 k Da ha stronger hygroscopic.Chose it to the next step of the experiment and explore the dynamic distribution of moisture migration during moisture absorption.(2)In the study of long-term moisture regulation of dynamic migration and distribution under condition of high humidity moisture at RH 80% with the help of LF-NMR,the morphology changes,total weight of sample,the moisture absorption process of each component in the water changes and the dynamic migration distribution of sample moisture were studied.The experimental results show that the corn antioxidant peptide powder of molecular weight less than 1 k Da in the process period of 15 days continued to absorb water and the powder sample gradually achieve complete liquefaction.It was complete liquefaction in fifth days.In the process of moisture absorption for 15 days,the quality of the sample increased continuously,and the moisture absorption rate of the sample decreased continuously.The LF-NMR indicated that the corn antioxidant peptide powder samples with molecular weight less than 1 k Da had two different proton groups with different degrees of freedom in the presence of moisture absorption.The T2 relaxation time of first component is less than 10 ms,relatively stable.The T2 relaxation time of first component is less than 10 ms,relatively stable,the second component the water T2 relaxation time is between 10~100 ms,relatively unstable.In the process of moisture absorption,there exists a double hump in the proton signal of the two kinds of components.The proton exchange of the two kinds of components is constantly changing in the process of moisture absorption.At sixth days,when the sample has just reached full liquefaction,the ratio of the two proton components to the total signal is 48.815% and 51.185%,respectively,which is the equilibrium state of the water of the two components in the system.(3)In the study of the effect of moisture on the quality characteristics of corn peptide powder,corn antioxidant powder peptides with molecular weight less than 1 k Da were chosen as the research object.The study analyzes the changes of Zeta potential,particle size,antioxidant activity,and secondary structure of corn antioxidant peptide powder in 25 ℃ 80 % humidity conditions after moisture absorption.The experimental results show that there are certain influences of moisture on quality characteristics of corn peptide powder.Over the moisture absorption process,the partical size of the sample increases,the absolute value of Zeta potential decreases,and the stability of the whole sample system is declining,in the ESR experiment,the hydroxyl radical scavenging antioxidant activity of sample decreases gradually,received a great impact in the absorption process,while the CD experiment has indicated that the water absorption does not affect the second structure of the sample in the whole process. |
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