FIELD: analytical methods in food industry. SUBSTANCE: invention relates to electrochemical methods of analysis of carbohydrates, in particular to potentiometric method for quantitative determination of fructose (reducing sugar), which can be used as chemico-technological control of fructose in milk industry. Method consists in that a sample to be analyzed is neutralized with 30% sodium hydroxide solution to pH 9.00-9.20 and then added to 0.00125 M sodium tetraborate reagent solution at ratio 1:4 and pH of mixture is measured potentiometrically. To calculate fructose concentration (Cx), difference between pH of reagent solution and pH of reagent solution-sample mixture (ΔpH) as well as difference between pH of reagent solution and pH of reagent solution-sour milk base mixture (ΔpHф,) are measured and fructose concentration is calculated from equation: Cx = 1.12(ΔpH-ΔpHф)) wherein coefficient of proportionality 1.12 is found experimentally. Value of ΔpHф varies between 0.12 and 0.23. Fructose determination range is 0.05-0.5 g/100 cu.cm. EFFECT: increased determination accuracy. 3 cl, 1 dwg, 1 tbl, 4 ex
