Rationale: Oxygen isotope analysis of water molecules of liquid foodstuffs is commonly done under isotopic equilibrium between water in the solution and its vapour water assuming that the liquid water activity is equal to unit and that liquid water is an ideal mixture of H2O isotopologues. A priori this behaviour is not realistic for all foodstuffs, which frequently are very concentrated solutions. In this paper we prevalently consider “balsamic vinegar” with the aim of defining an appropriate procedure of oxygen isotope analysis of water molecules in these concentrated solutions. Methods: IRMS measures of the oxygen isotopes, 18O, were carried out on CO2 equilibrated with water molecules at 22  0.1°C. Three independently calibrated very low salinity waters were used as standards. Results: For grape must and wine vinegar (density < 1.15 g/cm3 ), the 18O values for water determined directly on these solutions are “true” values. On the contrary, for balsamic vinegar with density higher than about 1.20 g/cm3, the 18O values obtained directly on the solutions are systematically different from those obtained on water produced by distillation of the same samples at 70°C under vacuum. Conclusions: In the case of balsamic vinegar with density higher than about 1.20 g/cm3, to avoid severe systematic errors, the isotopic analyses must be carried out on water obtained by distillation under stirring.

18/16O in water of concentrated liquid foodstuff: are the commonly determined values accurate? / Iacumin, Paola; DI MATTEO, Antonietta; Selmo, Enricomaria; Venturelli, Giampiero. - In: RAPID COMMUNICATIONS IN MASS SPECTROMETRY. - ISSN 0951-4198. - 32:20(2018), pp. 1751-1754.

18/16O in water of concentrated liquid foodstuff: are the commonly determined values accurate?

Paola Iacumin
;
Antonietta Di Matteo;Enricomaria Selmo;
2018

Abstract

Rationale: Oxygen isotope analysis of water molecules of liquid foodstuffs is commonly done under isotopic equilibrium between water in the solution and its vapour water assuming that the liquid water activity is equal to unit and that liquid water is an ideal mixture of H2O isotopologues. A priori this behaviour is not realistic for all foodstuffs, which frequently are very concentrated solutions. In this paper we prevalently consider “balsamic vinegar” with the aim of defining an appropriate procedure of oxygen isotope analysis of water molecules in these concentrated solutions. Methods: IRMS measures of the oxygen isotopes, 18O, were carried out on CO2 equilibrated with water molecules at 22  0.1°C. Three independently calibrated very low salinity waters were used as standards. Results: For grape must and wine vinegar (density < 1.15 g/cm3 ), the 18O values for water determined directly on these solutions are “true” values. On the contrary, for balsamic vinegar with density higher than about 1.20 g/cm3, the 18O values obtained directly on the solutions are systematically different from those obtained on water produced by distillation of the same samples at 70°C under vacuum. Conclusions: In the case of balsamic vinegar with density higher than about 1.20 g/cm3, to avoid severe systematic errors, the isotopic analyses must be carried out on water obtained by distillation under stirring.
18/16O in water of concentrated liquid foodstuff: are the commonly determined values accurate? / Iacumin, Paola; DI MATTEO, Antonietta; Selmo, Enricomaria; Venturelli, Giampiero. - In: RAPID COMMUNICATIONS IN MASS SPECTROMETRY. - ISSN 0951-4198. - 32:20(2018), pp. 1751-1754.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11381/2849709
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