METHOD FOR DETERMINATION OF PECTINS WEIGHT FRACTION IN MARMALADE Russian patent published in 2013 - IPC G01N33/02 

FIELD: food industry.

SUBSTANCE: one prepares gauging solutions with pectin weight fraction equal to 1.0%, 2.0%, 3.0%, 5.0%; into 25 cm³ measuring flasks one places 0.25 g, 0.50 g, 0.75 g and 1.25 g of pectin respectively. Then one adds 10 cm³ of distilled water into each flask and heats the flasks in a water bath at a temperature of 40-50°C until complete dissolution of pectin. The solutions are diluted to volume with distilled water. The gauging solutions, beginning with the least concentration, are alternatively placed into the FTIR (frustrated total internal reflection) pan of an IR spectrophotometer so that the pan bottom is fully covered. Spectre is registered within the range of wave numbers from 1755 cm^-1 to 1745 cm^-1. In the gauging solution spectre record a line is drawn through the 1753 cm^-1 and 1746 cm^-1 frequency points. One measures the solution absorption in optic density units at frequencies equal to 1753, 1749 and 1746 cm^-1. One calculates the absorption peak height A for the wave number equal to 1749 cm^-1(optic density units) from the formula: $$A=A_0-\frac{A_1+A_2}{2},$$ where A₀ - solution absorption at a frequency of 1,749 cm^-1, optic density units, A₁ - solution absorption at a frequency of 1753 cm^-1, optic density units, A₂ - solution absorption at a frequency of 1,746 cm^-1, optic density units; then one draws a gauging graph within the following coordinates: absorption peak height A for the wave number equal to 1749 cm^-1 A, optic density units (axle y) - pectin weight fraction T, % (axle x). Marmalade in an amount of 12.5 g, weighed with accuracy equal to ±0.2 mg, is placed into a 25 cm³ measuring flask via a funnel. One adds 10 cm³ of distilled water and performs heating in a water bath until complete dissolution of pectin. The solution is diluted to volume with distilled water. The solution is placed into a pan so that the pan bottom is fully covered. Spectre is registered within the range of wave numbers from 1755 cm^-1 to 1745 cm^-1. One measures the absorption peak height for the wave number equal to 1749 cm^-1. From the gauging graph, one identifies the weight fraction of pectins in the solution under study T, %, the weight fraction of pectins in the sample under study M calculated from the formula: M = 0.44 · T, where 0.44 - correction coefficient accounting for influence of organic acids contained in the product; T - weight fraction of pectins in the solution under study, %.

EFFECT: method enables fast and accurate identification of pectin in products with any sugar content which ensure determination of pectin weight fraction with lower labour intensity.

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