Differential pHmeter Determination of Residual Sugars in Wine

¹ Dipartimento di Scienza degli Alimenti, Facoltà di Agraria, Università di Napoli Federico II, I-80055 Portici, Italy.

email: moio{at}unina.it

A simple and rapid electrochemical procedure for the analysis of total glucose and fructose based on phosphorylation of the two reducing sugars by ATP and catalyzed by hexokinase was applied to wine. The oxidative phosphorylation of glucose and fructose produce H⁺ ions. An automated software-controlled differential pHmeter was used for H⁺ detection and the pH measured was correlated to the total glucose and fructose concentration present in the sample. Total glucose and fructose was measured in the range 2 to 30 g/L. Recovery studies were carried out to evaluate the effect of wine matrices on total glucose and fructose determination. The recovery was between 100 and 102%. The procedure based on differential pH-measurement gave results comparable with the reference method of the European Community n. 2676/90. The proposed method was simple and rapid because no previous treatment of the sample was required for measurement and data were automatically recorded. This method could be a valid alternative to the Lane-Eynon method for routine determination of total glucose and fructose in wines.

Note:
Acknowledgments: The authors thank the EUROCHEM Technologie Analitiche, Ardea (Rome), for their collaboration. The skillful assistance of Caroline S. Turner, M. Agr. Sc., is also gratefully acknowledged.

Key words: Reducing sugars, glucose, fructose, differential pH, wine

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