NMR And MRI Techniques Application In Food Science

The use of conventional NMR and MRI apparatus and the application of NMR/MRI techniques are well established in medicine,chemistry and physics,but not in food science, especially in China.This research has demonstrated that a number of NMR and MRI developed are excellent techniques for analysis of the physiochemical properties associated with the shelf life of food.The information obtained with the NMR and MRI techniques can help understand physiochemical changes at molecular level,and may be used to guide basic food research and food product and process development.These non-destructive and non-invasive techniques can be easily adapted to other food systems,opening many opportunities for better understanding of food processes and shelf life stability in general.MRI offers the possibility to perform measurements non-invasively and non-destructively to study the structure or to trace structural changes or transport processes inside the sample without special preparations and unpredictable modifications caused by the measurement.Thus it is not only possible to detect and quantify the static structure,but also to monitor dynamic structural changes and processes during production,storage,transportation,and even consumption of food-products with temporal,spatial and chemical resolution(multidimensional).NMR enables, therefore,repetitive testing of dynamic processes including enzymic and non-enzymic chemical reactions.The overall objective of the present work is to introduce and adapt NMR/MRI techniques into food science and solve the basic technical problem.The first specific research aim of present work was to evaluate and develop NMR and MRI pulse sequences suitable for studies important to the accomplishment of my research objective.The spin-echo(SE)pulse sequence,the Carr Purcell Meiboom Gill(CPMG)pulse sequence,and the inverse recovery(IR)pulse sequency were tested on orange.How to design pulse sequences by visual programs to obtain T₁/T₂ weighted MRI images and how to eliminate the fake images were also discussed.Necessary adjustments and settings of the NMR experimental parameters were proposed accordingly.The second specific research aim was to study the method of calculating and producing T₂ mapping by computer programs designed using Delphi 7.0 software.This work is involved two different fields,one is computer program design and the other is food science.Therefore,it maybe difficult to be fully understood by food scientists region having no computer background. But T₁/T₂ mapping is very important for the NMR/MRI technology and its application in food science.The third specific research aim was to monitor the state of water and understand the behavior of water in bread and cheese during storage using self-designed programs mentioned above paragraphs,which is important to the evaluation of the effect of water transfer between components on shelf life stability.MRI T₂mapping was used to observe the moisture movement between a cheese block and bread block closely packed together in a closed system.The results show that moisture transfer from cheese to bread increased with increasing time.It was found that addition of lipid to the bread promoted moisture movement from cheese to bread.The fourth specific aim was to design and make an accessorial temperature control equipment to carry on NMR state diagram research.The new concept is called "NMR state diagram," which is a plot of relaxation lime vs.temperature.The concept could be used to explain the relationship between the physiochemical states and interactions of water and solids in food systems.The theoretical principles and experimental evidence are presented.This concept appears to land itself best in the study of shelf life of food polymers.This works follow the newest study in the international and firstly develop the NMR State Diagram study in domestic.The fifth specific aim was to understand the relation between Mallard Reaction and NMR state diagram transition point temperature using the newly developed NMR State Diagram Concept.Effects of NMR state diagram and transition point(Tp)temperature on Mallard Reaction rale between lysinc and glucose in a non-crystallizing trehalose-sucrosc-water matrices were studied.Trends of Tp temperatures change in the NMR state diagram were observed in the model matrices with different moistures and sugar contents.A relative higher Tp temperature was observed in the low moisture sugar matrix and a relative slow reactive velocity was observed in the identical matrix during storage at the same time.There were obvious reactive velocity differences on the temperatures above and below the Tp temperatures by detecting the rates of reaetant consumption in the matrices for the Mallard reaction during storage at different temperatures.Different reactive velocities were observed in the samples having different sugar contents with same moisture during storage under same temperature.It is concluded that NMR state diagram and Tp temperature is a very useful technique and parameter in assessing the better storage temperature and in ingredient design for the extension of food shelf-life by decreasing the relative chemical reaction velocity during storage,since the NMR state diagram and Tp temperatures were influenced by the sugar contents,moisture,and state of water.These experimental data can also be used to illustrate the significance of NMR State Diagram in food storage research and in ingredient screening and formula design for extending the shelf life of food.This research has demonstrated that a number of NMR and MRI techniques developed are excellent tools for analysis of the physiochemical properties associated with food making processes and shelf life extension.The information obtained with the NMR and MRI techniques can help with the understanding of physiochemical changes at molecular level,and may be used to guide basic food and other polymer research and product and process development.These non-destructive and non-invasive techniques can be easily adapted to other food and polymer systems,opening many opportunities for better understanding of food and other polymer processes and shelf life stability in general.