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Abstract:

Water - solid interactions were analyzed in potato samples in a wide range of relative humidities (RHs) by means of proton nuclear magnetic resonance ( 1 H NMR), differential scanning calorimetry (DSC), and water - sorption isotherms. Nonenzymatic browning development was studied at 70 ° C and in relation to the physical properties of the samples. Proton relaxation was analyzed by 1 H - NMR measurements. The spin -spin relaxation time ( T 2 ) attributed to the fast - relaxing protons (from solids and most tightly associated water molecules) was measured using a free - induction decay (FID) analysis. The T 2 associated with the slow - relaxing protons of water molecules was measured by using the Hahn spin - echo pulse sequence. The FID analysis showed a single T 2 component at around 7- 20 ì s, which was associated with the mobility of the polymer chains. Samples between 11% and 52% RH showed a slight increase in T 2 values as the RH increased and did not change along the temperature scale signifi -cantly. The systems at 75%, 84%, and 93% RH presented much higher T 2 values because of the plasticizing effect of water and showed a marked increase in T 2 along the temperature scale close to the glass transition. The Hahn analysis showed two components. A short component on the order of 30 ì s, present at all the RHs analyzed, which corresponds to solid polysaccharide protons as the T 2 measured by FID analysis. Above 22% RH, a long component in the range of 400 - 950 ì s, which refl ects the relaxation time of water protons, was also observed the value of which increased with the increase in water content. Nonenzymatic browning was detected in the glassy state; however, the maximum color development was detected at 84% RH, well above the glass transition temperature ( T T g = 40 ° C), and then, above this RH, the reaction rate decreased, coinciding with the appearance of freezable water (determined by DSC) and with the higher T 2 values. The integrated analysis of the water sorption, water, and solids mobility and of thermal transitions aids in the interpretation of the mechanisms and kinetics of chemical reactions.

Registro:

Documento: Parte de libro
Título:Proton Nuclear Magnetic Resonance Studies of Molecular Mobility in Potato Systems in Relation to Nonenzymatic Browning
Autor:Acevedo, N.C.; Schebor, C.; Buera, M.D.P.
Filiación:Departamento de Industrias, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
Departamentos de Industrias y de Química Orgánica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
Palabras clave:Fast-relaxing protons spin-spin relaxation time measurement-free-induction decay (FID); H NMR-analyzing water-solid interactions in potato sample; H NMR-proton nuclear magnetic resonance; Molecular mobility in potato systems-proton nuclear magnetic resonance studies; NEB kinetics-water mobility in freeze-dried potato systems; Nonenzymatic browning (NEB)-affecting food quality in processing and storage; Water mobility and chemical reactivity in low-moisture solids
Año:2010
Página de inicio:437
Página de fin:443
DOI: http://dx.doi.org/10.1002/9780470958193.ch33
Título revista:Water Properties in Food, Health, Pharmaceutical and Biological Systems: ISOPOW 10
Título revista abreviado:Water Prop. in Food, Health, Pharmaceutical and Biol. Syst.: ISOPOW 10
Registro:https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_97808138_v_n_p437_Acevedo

Referencias:

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Citas:

---------- APA ----------
Acevedo, N.C., Schebor, C. & Buera, M.D.P. (2010) . Proton Nuclear Magnetic Resonance Studies of Molecular Mobility in Potato Systems in Relation to Nonenzymatic Browning. Water Properties in Food, Health, Pharmaceutical and Biological Systems: ISOPOW 10, 437-443.
http://dx.doi.org/10.1002/9780470958193.ch33
---------- CHICAGO ----------
Acevedo, N.C., Schebor, C., Buera, M.D.P. "Proton Nuclear Magnetic Resonance Studies of Molecular Mobility in Potato Systems in Relation to Nonenzymatic Browning" . Water Properties in Food, Health, Pharmaceutical and Biological Systems: ISOPOW 10 (2010) : 437-443.
http://dx.doi.org/10.1002/9780470958193.ch33
---------- MLA ----------
Acevedo, N.C., Schebor, C., Buera, M.D.P. "Proton Nuclear Magnetic Resonance Studies of Molecular Mobility in Potato Systems in Relation to Nonenzymatic Browning" . Water Properties in Food, Health, Pharmaceutical and Biological Systems: ISOPOW 10, 2010, pp. 437-443.
http://dx.doi.org/10.1002/9780470958193.ch33
---------- VANCOUVER ----------
Acevedo, N.C., Schebor, C., Buera, M.D.P. Proton Nuclear Magnetic Resonance Studies of Molecular Mobility in Potato Systems in Relation to Nonenzymatic Browning. Water Prop. in Food, Health, Pharmaceutical and Biol. Syst.: ISOPOW 10. 2010:437-443.
http://dx.doi.org/10.1002/9780470958193.ch33