Honey

(Ph. Eur. monograph 2051)

DEFINITION

Honey is produced by bees (Apis mellifera L.) from the nectar of plants or from secretions of living parts of plants which the bees collect, transform by combining with specific substances of their own, deposit, dehydrate, store and leave in the honey comb to ripen and mature.

PRODUCTION

If the bee has been exposed to treatment to prevent or cure diseases or to any substance intended for preventing, destroying or controlling any pest, unwanted species of plants or animals, appropriate measures are taken to ensure that the levels of residues are as low as possible.

CHARACTERS

Appearance

Viscous liquid which may be partly crystalline, almost white to dark brown.

IDENTIFICATION

Thin-layer chromatography (2.2.27).

Test solution: Dissolve 0.6 g of the substance to be examined in 50 mL of ethanol (30 per cent V/V) R.

Reference solution: Dissolve 0.5 g of fructose R, 0.5 g of glucose R and 0.1 g of sucrose R in 100 mL of ethanol (30 per cent V/V) R.

Plate TLC silica gel plate R.

Mobile phase water R, acetonitrile R (13:87 V/V).

Application 5 μL as bands.

Development 3 times over a path of 15 cm.

Drying In warm air.

Detection: Spray with a solution prepared as follows: dissolve 2 g of diphenylamine R and 2 mL of aniline R in 100 mL of acetone R. Add a 850 g/L solution of phosphoric acid R until the precipitate formed dissolves again (about 15-20 mL).

Examine in daylight after heating at 100-105 °C for 5-10 min.

Results See below the sequence of the zones present in the chromatograms obtained with the reference solution and the test solution. Furthermore, the weak brown zone due to sucrose in the chromatogram obtained with the reference solution may be present in the chromatogram obtained with the test solution.

One or more other weak zones may be present in the chromatogram obtained with the test solution.

TESTS

Refractive index (2.2.6)

Minimum 1.487 (equivalent to a maximum water content of 20 per cent).

Homogenise 100 g and transfer into a flask. Close tightly and place in a water-bath at 50 ± 0.2 °C until all sugar crystals have dissolved. Cool the solution to 20 °C and rehomogenise. Immediately after rehomogenisation, cover the surface of the refractometer prism evenly with the sample. Determine the refractive index after 2 min if using an Abbe refractometer and after 4 min if using a digital refractometer.

Use the average value of 2 determinations.

Conductivity (2.2.38)

Maximum 800 μS·cm .

Using the value obtained for the refractive index, determine the water content of the substance to be examined from

Table 2051.-1. Using this information, dissolve an amount of the substance to be examined equivalent to 20.0 g of honey dry solids, in water R to produce 100.0 mL.

Optical rotation (2.2.7)

Maximum + 0.6°.

Using the value obtained for the refractive index, determine the water content of the substance to be examined from

Table 2051.-1. Using this information, dissolve an amount of the substance to be examined, equivalent to 20.0 g of honey dry solids, in 50 mL of water R. Add 0.2 mL of concentrated ammonia R and dilute to 100.0 mL with water R. If necessary decolourise the solution with activated charcoal R.

Table 2051.-1. – Relationship of water content of honey to refractive index

5-Hydroxymethylfurfural

Maximum 80 ppm, calculated on dry solids.

Using the value obtained for the refractive index, determine the water content of the substance to be examined from Table 2051.-1. Using this information, dissolve an amount of the substance to be examined, equivalent to 5.0 g of honey dry solids, in 25 mL of water R and transfer to a 50.0 mL volumetric flask with the same solvent. Add 0.5 mL of a 150 g/L solution of potassium ferrocyanide R and mix. Add 0.5 mL of a 300 g/L solution of zinc acetate R, mix and dilute to 50.0 mL with water R (a drop of anhydrous ethanol R may be added to avoid foaming). Filter. Transfer 5.0 mL of the filtered solution into each of 2 tubes. To one tube add 5.0 mL of water R (test solution). To the other tube add 5.0 mL of a 2.0 g/L solution of sodium hydrogensulfite R (reference solution). Determine the absorbance (2.2.25) of the test solution against the reference solution at 284 nm and 336 nm within 60 min. If the absorbance at 284 nm is greater than 0.8, dilute to the same extent the test solution with water R and the reference solution with a 2.0 g/L solution of sodium hydrogensulfite R so as to obtain an absorbance of less than 0.8.

Calculate the content of 5-hydroxymethylfurfural from the expression:

(A₁−A₂)×D×149.7

A₁ = absorbance at 284 nm,

A₂ = absorbance at 336 nm,

D = dilution factor, where applicable.

Chlorides (2.4.4)

Maximum 350 ppm, determined on 15 mL of a 10 g/L solution.

Sulfates (2.4.13)

Maximum 250 ppm, determined on 15 mL of a 40 g/L solution.