The Application of SDS-PAGE Protein and HPTLC Amino Acid Profiling for Verification of Declared Variety and Geographical Origin of Honey

Abstract

Proteins and amino acids are minor components of honey that are rarely used for its quality evaluation, although these components create its biological activity as well as can serve for overheating detection. The aim of the study was to use these indicators to confirm a declared on the label variety. Fifty-eight honey samples of 8 different varieties meeting the commercial quality requirements were used, including 28 local Polish and 30 commercial (mainly imported from EU and non-EU) honeys. For honey protein profiling previously used, polyacrylamide electrophoresis in denaturing conditions (SDS-PAGE) was applied whereas the free amino acid profile was analyzed by high-performance thin-layer chromatography (HPTLC) for the first time. As auxiliary indicators, the colorimetric determination of the protein content by the Bradford method, the activity of 5 glycolytic enzymes, including diastase, β-galactosidase, N-acetyl-β-glucosaminidase, α-mannosidase, and α-glucosidase, and the content of proline were used. It has been shown that based on the determined model protein SDS-PAGE profiles for selected monofloral honeys, it is possible to detect honeys of questionable variety based on the lack of specific protein bands or their diverging intensity. The HPTLC amino acid analysis can serve as a supporting control tool, capturing differences in the amino acid profile. Due to a great variation of multifloral honey, such assays are effective for monofloral honey only. The colorimetric assays, especially for total protein and β-galactosidase, can be also useful. The applied tools can be proposed for the initial verification of honey variety for cost reduction of officially recognized melissopalynological analysis.