CS257566B1 - A method for determining sucrose in honey - Google Patents

Abstract

Method for determining sucrose in honey, based on the reaction of sucrose hydrolysis of the resulting D-glucose and D-fructose with concentrated sulfuric acid and the subsequent reaction of the resulting 5-hydroxymethylfurfural with anthrone. Interfering monosaccharides and reducing disaccharides are removed from the analyzed honey sample before the actual hydrolysis of sucrose by the action of alkali metal hydroxide. The method of determination consisting in the addition of concentrated sulfuric acid and anthrone in ethyl acetate with the addition of stabilizing acetic or formic acid allows for a subjective evaluation of the resulting color shade with an accuracy of determination of ±1% by weight of sucrose at a total sucrose content of 10% by weight. The method for determining sucrose according to the solution thus allows monitoring the quality of honey already when it is purchased "in the field" outside the chemical laboratory

Description

The invention relates to a method for determining sucrose in honey by a simple rapid visual colorimetric method that can be applied directly in honey buyers without having to work in a chemical laboratory associated with the use of the necessary apparatus.

From the point of view of determining the quality of honey, one of the decisive criteria is the sucrose content, especially in relation to the authenticity of bee honey. The amount of sucrose present can be determined directly using some chromatographic technique (eg HPLC on modified silica gels - Thean, JE, Funderburg, WC Jr. 1977, J. AOAC 60, 838-841) or ion exchangers (Palmer, J, K., Brandes ,

1974 W. J. Agric. Food Chem. 22, 709-712), optionally by gas chromatography after appropriate conversion of sucrose to volatile derivatives (Zurcher, K., Hadorn, H., Straek, Ch., 1975, Mitt. Geb. Lebensm. Hyg. 66, 92-116).

More frequently, however, the sucrose content is determined after its hydrolysis to an equimolar mixture of D-glucose and D-fructose. The most common method based on this principle is the polarimetric determination of sucrose (Simpson, J. 1952, Bee World 33, 112-117.). In contrast, procedures based on determining the content of reducing monosaebarides formed (Simpson, J, 1960, J. Insect. Physiol. 4, 107-121) are complicated by the high content of contaminating monosaccharides and oligosaccharides (mainly maltose) for the determination of sucrose in honey.

In the VanHandel procedure (VanHandel, E. 1968, Anal. Biochem. 22, 280-283), these interfering monosaccharides are first decomposed by the action of a strong base, and then the acid hydrolysis of sucrose remains in the previous step in a strongly alkaline environment. . bathtub. The monosaccharides formed by the hydrolysis of sucrose are then determined by thermal dehydration in the presence of acids and subsequent condensation of the resulting 5-hydromethylfurfural with coloring agents (mostly aromatic amines, phenols or ketones). The absorbance of the reaction mixture is proportional to the content of D-glucose and D-fructose present in the sucrose hydrolysis solution.

The use of dilute sulfuric acid with anthrone and external heating of the reaction mixture (VanHandel procedure) produces a blue-green color, the intensity of which must be evaluated objectively by photometers, since the color variations are subjectively difficult to compare. The VanHandel process requires twice the external heating of the reaction mixture, of which once the heating accuracy will directly affect the color intensity.

The essence of the invention is a quantitative determination of sucrose in which interfering saccharides are removed in an alkaline medium and then, in addition to Van Handel, a solution of anthrone in ethyl acetate is added to the honey solution by adding stabilizing acetic acid to prevent anthrone condensation ethyl acetate. Heat for the condensation reaction is obtained by adding sulfuric acid (a combination of dilution heat and enthalpy balance of the reaction of potassium hydroxide, ethyl acetate, acetic acid, sulfuric acid).

The advantage of the method of determination of sucrose in honey according to the invention is mainly the speed of determination, low demands on performance even for unqualified forces and further the possibility of subjective assessment of the color tint produced in the area of human susceptibility (yellow to blue-green tint). in honey without the use of photometers or other instruments.

Advantages of the assay also include a higher stability of the anthron solution in ethyl acetate compared to the anthron solution in dilute sulfuric acid as used in the original Van Handel process. The stability of anthrone in ethyl acetate is several days, after addition of stabilizing organic acids up to several weeks. In contrast, in the Van Handel trial, anthrone reagent should be prepared daily. The dye formed is sufficiently stable for at least 75 minutes in the embodiment described.

In addition to the advantages of the assay method of the invention, there is also a simple method of collecting and dispensing liquid and crystalline honey by volume using a syringe. The weighing of the exact amounts of honey is time consuming and therefore this process represents a considerable time saving, notwithstanding the unrealistic weighing of 1 g of honey with an accuracy of 2% in conditions outside the laboratory.

In a practical embodiment, the use of semi-automatic glass dispensers with a Teflon piston has also greatly accelerated the process, which at the same time has increased the safety of work during the actual determination under practical conditions. At present, this method is widespread when buying honey practically throughout the SSR.

The advantage of the method of determination of sucrose in honey according to the invention is the time saving in the actual determination, which is considerably material and time-consuming than the previously used polarimetric determination. The accuracy of the subjective colorimetric determination according to the invention is 1% of sucrose content with a total honey content of 10% by weight. The method of determination is so simple that it can also be performed by an unskilled worker after brief training. The method of determining sucrose according to the invention therefore enables the quality of honey to be monitored even when purchased outside a chemical laboratory.

The invention is illustrated by the following non-limiting examples.

He did

Using a 2 ml syringe, measure 0.7 ml of the test honey into a 100 ml graduated cylinder with a stopper and dissolve to 100 ml with water (distilled or commercial) - solution A.

Cut the vial with 0,1 g of anthrone and dissolve in 5 ml of ethyl acetate with the addition of a stabilizer (5 ml of glacial acetic acid per 100 ml of ethyl acetate) - solution B.

Preparation of the color standard: To 0.1 ml of standard sucrose solution (0.1 g / 100 ml), add 0.2 ml of potassium hydroxide solution (30 g / 100 ml) and heat on a water bath at 80 to 100 ° C for 10 minutes. After cooling, add 0.5 ml of solution B and 3.5 ml of concentrated sulfuric acid. Mix.

Determination: To 0.1 ml of solution A add 0.2 ml of 30% (v / o) potassium hydroxide solution, heat in a water bath at 80 to 100 ° C for 10 minutes and after cooling add 0,5 ml of solution B and 3.5 ml of concentrated sulfuric acid. Mix and compare the color with the standard. The solutions can be objectively compared spectrophotometrically at 620 nm.

The sensitivity of the subjective assay is ± 1 wt. % sucrose at a total content of 10 wt. Duration of analysis including sample preparation and heating for 17 to 20 minutes.

Example 2

Solution A - according to Example 1

Cut an ampoule with 0,1 g of anthrone and dissolve in 5 ml of ethyl acetate with the addition of a stabilizer (7 ml of 98% (by volume) formic acid per 100 ml of ethyl acetate) solution B. Preparation of color standard: To 0,1 ml of standard sterile solution sucrose (0.1 g / 100 ml) from the cut ampoule, add 0.2 ml of sodium hydroxide solution (25 g / 100 ml) and heat on a water bath at 100 ° C for 5 minutes. After cooling, add 0.5 ml of solution B and 3.5 ml of concentrated sulfuric acid. Mix.

Determination: To 0.1 ml of solution A add 0.2 ml of 25% (v / o) sodium hydroxide solution, heat in a water bath for 5 minutes at 100 ° C and after cooling add 0,5 ml of solution Ba 3,5 ml concentrated sulfuric acid. Mix and compare the color to the standard (for 10% by weight of sucrose in honey). The sensitivity of the assay is ± 1% w / w. % sucrose with a total content of 10 wt. sucrose.

Stability of chemicals and solutions:

hydroxide solutions - unlimited in closed bottle anthron - 3 years ethyl acetate with stabilizers - unlimited in closed bottle concentrated sulfuric acid - unlimited sterilized sucrose solution - 4 years stability of solution B - 2 months

Example 3

Using a 2 ml syringe, measure 0.7 ml of honey into a 1000 ml volumetric flask and make up to 1000 ml with water (ordinary or distilled) - solution A.

Solution B - Dissolve 0,5 g of anthrone in 100 ml of ethyl acetate with the addition of a stabilizer (10 ml of acetic acid per 100 ml of ethyl acetate).

Preparation of color standard: To 0.1 ml of standard sucrose solution (0.01 g / 100 ml) add 0.2 ml of 5% (v / o) NaOH solution, heat on a water bath at 100 ° C for 5 minutes. After cooling, add 0,5 ml of solution B and 0,8 ml of concentrated sulfuric acid, mix.

Determination: To 0.1 ml of solution A add 0.2 ml of 5 «(v / o) NaOH solution, heat for 5 minutes at 100 ° C, add 0.5 ml of solution B and 0.8 ml of concentrated sulfuric acid after cooling. , mix. The resulting color is compared to the standard at 620 nm.

Example 4

Solution A - see Example 1

Solution B - Dissolve 2.5 g of anthrone in 50 ml of ethyl acetate stabilized with acetic acid (20 ml of concentrated acetic acid in 100 ml of ethyl acetate).

Determination: To 0.1 ml of solution A add 0.2 ml of 5% (v / o) potassium hydroxide solution, heat for 10 minutes at 80 to 100 ° C. After cooling, add 0.5 ml of solution B and 7 ml of concentrated sulfuric acid, mix.

Preparation of the color standard: To 0.1 ml of standard sucrose solution (0.1 g / 100 ml) add 0.2 ml of 5% w / w. solution of KOH, heat for 10 minutes at 80 to 100 ° C, cool, add 0.5 ml of solution B and 7 ml of conc. sulfuric acid. Compare spectrophotometrically at 620 nm with self-determination or subjectively. Method sensitivity and analysis duration as in Example 1.

Claims (1)

Method for the determination of sucrose in honey by colorimetry, characterized in that the mixture of 1 wt. 100 parts by weight of honey, measured by volume with a syringe, are mixed with 100 to 1000 wt. parts of water and 10 to 100 wt. The mixture is heated at 80-100 ° C for 5-15 minutes, and then 5-100 wt. % of anthrone in the form of 0.5 to 5 wt. % of a solution in ethyl acetate stabilized by the addition of 1 to 20% by volume of concentrated acetic or formic acid, and then 1000 to 15,000 wt. of concentrated sulfuric acid, and then the sucrose content is evaluated by determining the absorbance of the mixture at 620 nm, or subjectively by comparison with a standard.