MRI indicators for measuring pH and redox in food

Webb, Gisela; Belton, Peter; Gil, Antonio; Delgadillo, Ivonne; Evans, S. D.; Hall, Laurance D.

doi:10.1039/9781847551252-00022

Cited by 2 publications

(3 citation statements)

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“…The indicator range can be further tuned by varying the ratio of the metal ion to the chelating agent. Complexes of manganese (Mn) ions have the advantage that since manganese ions are more paramagnetic than copper ions, a lower concentration can be used; importantly, since manganese ions induce changes in T 2 T 2 T values as well as T 1 rates, advantage can be taken of the fact that MRI mapping of T2 values is faster than mapping of T 1 values (Evans and Hall, 2001).…”

Section: M+l MLmentioning

confidence: 99%

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Measurement of pH in Food Systems by Magnetic Resonance Imaging

Evans

Hall

2008

Can. J. Chem. Eng.

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P robably the fi rst chemistry measurement most of us make in school is to use a strip of litmus paper to measure the acidity of various foods; we subsequently graduate to using a pH meter to study reactions in the laboratory, and our taste-buds in the home to evaluate our foods. This article will demonstrate that this connection between the laboratory and the home is not fanciful; rather, that it can be achieved in practice by magnetic resonance imaging (MRI) using the simple, yet effective, concept of the MRI equivalent of the coloured dyes which are used in analytical chemistry as pH indicators. The sequence of MRI scans shown in Figure 1 illustrates the time course for a garlic clove whilst it was being pickled by immersion in vinegar. The grey scale intensity of the original MRI scans had been pre-calibrated against pH and the progressive decrease in the pH as the acetic acid diffuses into the garlic tissues is clearly visible as a decrease in greyscale intensity. Although this may appear to be a trivial example, achieving the appropriate pH during manufacture is critical to the subsequent safe storage of many foods and the MRI method reported here is the only Magnetic resonance imaging (MRI) has been used to measure the nuclear relaxation times of the protons of water containing low concentrations (0.4mM) of the diethylenetriaminepentaaceticacid complex of manganese. Given that the manganese-binding equilibrium is dependent on the local pH, this forms the basis of a physically non-invasive method for quantitation of pH in three dimensions. The basic concepts are briefl y described together with specifi c details of how this MRI method can be used to follow the pickling of garlic immersed in vinegar and of meatballs immersed in vinegar or a tomato sauce. Measurement of pH in Food SystemsOn a eu recours à l'imagerie à résonance magnétique (IRM) pour mesurer les temps de relaxation nucléaire des protons de l'eau contenant de faibles concentrations (0,4 mM) du complexe diéthylènetriaminepentaacéticacide du manganèse. Étant donné que l'équilibre de liaison du manganèse est dépendant du pH local, cette méthode forme la base d'une méthode physiquement non intrusive de quantifi cation du pH en trois dimensions. Les concepts de base sont brièvement décrits ainsi que des détails spécifi ques sur la manière dont cette méthode IRM peut être utilisée pour suivre la macération d'ail immergé dans du vinaigre et de boulettes de viande immergées dans du vinaigre ou de la sauce tomate.Keywords: MRI, pH, pickling, food, garlic, meatballs physically non-invasive methodology available for measuring the spatial and time dependence of pH in intact foods.The practical reality of an MRI-active pH indicator depends on the combination of three separate concepts. First, is the fact that the relaxation times of the proton nuclei of water molecules are substantially enhanced by addition of water-soluble paramagnetic metal ions; MRI of such solutions can provide spatial maps of those nuclear relaxation times and hence of the spatial dist...

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Section: M+l MLmentioning

confidence: 99%

“…For example, the combinations of Cu ions and ethylenediamenetetraaceticacid is sensitive in the range pH 1 to 3, whereas that of Cu and ethylenediamine is sensitive for pH 4 to 6 (Fischer and Hall 1994 (Evans and Hall, 2001). …”

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confidence: 98%

Measurement of pH in Food Systems by Magnetic Resonance Imaging

Evans

Hall

2008

Can. J. Chem. Eng.

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“…It has been previously demonstrated that null‐point MRI imaging can be used to visualize and measure the change in pH associated with sulfuric acid diffusing through polyacrylamide gels doped with Cu EDTA 35, 36, 37. A range of indicators for mapping a pH range of 3 to 5 in food systems has also been developed 38. However, for future applications, it is important to develop pH indicators for the entire pH range; that development requires evaluation of an almost limitless combination of metal ions and ligands and of environments in which to use these indicators.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of a range of MRI‐active pH indicators using a multiple‐sample method

Evans

Hall

2005

AIChE Journal

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MRI indicators for measuring pH and redox in food

Cited by 2 publications

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Measurement of pH in Food Systems by Magnetic Resonance Imaging

Measurement of pH in Food Systems by Magnetic Resonance Imaging

Evaluation of a range of MRI‐active pH indicators using a multiple‐sample method

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