Refracto-densimetric Method for Determining the Sugar and Alcohol Content of Wines, Wine Materials and Fortified Drinks

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Abstract

A rapid method for determining the sugar content and alcohol content of grape wines
with-out preliminary distillation of ethyl alcohol is proposed. The method is based on
measuring the refractive index and density of the sample and using the additivity principle of refracto-densimetric characteristics – the refraction intercept and specific refraction. The method can be used in laboratory conditions, and in the presence of pairs of immersion or flow refractometers and densimeters (densitometers) built into process tanks or product pipelines, it can be implemented in production. The method considers wines as pseudoternary mixtures of aqueous solutions of sugars (fructose : glucose 1 : 1), ethanol and organic acids (tartaric : malic 3 : 1 wt.). Other minor components of wines, close in refracto-densimetric characteristics to the acid benchmark, also implicitly contribute to the last component. The method has no concentration restrictions on the components to be determined. The trajectories of the fermentation process of sugar and grape must are shown on the Kurtz-Lorentz chemographic map. A simplified version of the method considers wines as binary mixtures of aqueous solutions of sugars and ethyl alcohol, in which case the composition of wines can be determined graphically using the Kurtz-Lorentz nomogram or calculated using a similar algorithm. The results of measuring wine samples show good agreement between certain composition indicators and those declared by producers.

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About the authors

Vyacheslav F. Nikolaev

Казанский национальный исследовательский технологический университет

Author for correspondence.
Email: NikolaevVF@corp.knrtu.ru
ORCID iD: 0000-0002-8742-8629

Doctor of Chemical Sciences, Professor

Russian Federation, Казань

Filius F. Zalaltdinov

Казанский национальный исследовательский технологический университет

Email: filus2022@yandex.ru

PhD student

Russian Federation, Казань

Shamil I. Gataullin

Казанский национальный исследовательский технологический университет

Email: journal@electronics.ru

Bachelor

Russian Federation, Казань

Victoria V. Minaeva

Казанский национальный исследовательский технологический университет

Email: journal@electronics.ru

Bachelor

Russian Federation, Казань

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Supplementary files

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2. Fig. 1. Dependences of the specific refraction sR of aqueous solutions of the main components of wines on the mass fraction of the component w

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3. Fig. 2. Dependences of the refractive intercept RI of aqueous solutions of the main components of wines on the mass fraction of the component w

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4. Fig. 3. Hydrostatic density meter. Designations: 1 – portable electronic scales (Rmax = 100 g, accuracy ± 0.001 g); 2 – U-shaped frame made of duralumin profile; 3 – rectangular frame made of copper wire with a wedge–shaped bend in the upper part, resting in the center of the scale bowl, and a hook in the lower part; 4 - loop made of fishing lines (∅0.12 mm) with a ring connecting the suspension 5 with the scales 1; 5 – glass suspension (~10 cm3) with a hook; 6 – beaker (~50 ml); 7 – lifting table (10 × 10 cm) (optional); 8 – density meter base

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5. Fig. 4. Correlation of the alcohol content of wine samples determined by the refractodensimetric method with the alcohol content stated by the manufacturer (not interval-wise)

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6. 5. Fermentation kinetics of sugar and grape must and approximating curves

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7. Fig. 6. Fermentation trajectories (refractodences) of sucrose and grape must on the Kurtz—Lorentz chemographic map and triangles of composition with reference vertices wALK, wSAH (W sugar; W fruit/ GLUK), W Acid

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8. 7. Kurtz–Lorentz nomogram for determination of alcohol content and sugar content of pseudo-two-component wines and aqueous solutions of mixtures of sugars and ethyl alcohol

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Copyright (c) 2025 Nikolaev V.F., Zalaltdinov F.F., Gataullin S.I., Minaeva V.V.