Study Of Peptide Components In Wheat And The Change During Processing

Wheat peptide is defined as a pool of all peptides ranging from dipeptides to complex structural peptides naturally in wheat which has nutritional effects,flavors,and biological activities.The great complexily and the wide dynamic range of relative peptide abundance and the capabilities of existing analytical methodologies severely challenge the study of peptides nutrition under food processing.In this context,this study aimed at wheat flour peptides and set up extraction method and detection method by MALDI-TOF respectively.The differences of Xinjiang Spring Wheat and Xinjiang Winter Wheat as well as trends and mechanisms of change of wheat peptides under various food processing and the relationship between change and nutritional quality were studied.Frist,16 kinds of Xinjiang Spring Wheat and Xinjiang Winter Wheat were measured by MALDI-TOF mass spectrometry to get the data of peptide species and peak intensity.MALDI-TOF spectrum coupled with hierarchical clustering(HCL),principal component(PCA),partial least squares discriminant analysis(PLS-DA)and orthogonal partial least squares discriminant analysis(OPLS-DA),to reveal the inherent differences between wheat cultivars.Five peaks were selected as the optimized profile to help differentiate between Xinjiang Spring Wheat and Xinjiang Winter Wheat.Furthermore,this approach showed a different applicability to study the Cultivar Identification,traceability and quality of wheat.Then,peptides of Zhongmai 895 throughout heating processes and freeze-thaw cycles were evaluated.Results showed that high molecular weight peptides decreased significantly after heating.At 150-210?,high molecular weight peptides declined gradually and medium molecular weight peptide increased first and then decreased,while small molecular weight peptides appeared.At 230? almost all peptides disappeared.When we fixed heating temperature and extended heating time,high molecular weight peptides dropped off sharply and at last died out,while smaller molecular weight peptides occurred and increased constantly.With the increased number of freeze-thaw cycles,peptides with other molecular weight increased except the very high molecular weight decreased.Water and enthalpy data were measured to explain the changes of peptides.At large,that the effect of processing on wheat peptides and transformation law from protein to peptide was preliminarily analyzed,which can provide a theoretical basis and proof for the change of nutrition during food process from the aspect of protein.