Differentiation of bee pollen samples according to the betaines and other quaternary ammonium related compounds content by using a canonical discriminant analysis

Abstract

In the last years, an increase has been observed in the adulteration of bee pollen. Consequently, different tools are required to authenticate the origin of this product, such as a study of the profile and composition of a specific family of compounds. The present study investigates the potential of betaines and related compounds as markers of the apiary of origin and harvest period of 71 bee pollen samples. These were collected from four apiaries (Pistacho, Tío Natalio, Monte and Fuentelahiguera), located in the same geographical area (Guadalajara, Spain) and sampled during three consecutive harvest periods in the same year (April-May, June, July-August). They were analyzed by means of a previously developed methodology, which involved solvent extraction, hydrophilic interaction liquid chromatography coupled to mass spectrometry, and a statistical analysis of the data (canonical discriminant analysis). Variable amounts of betaines and related compounds were found in the samples, with four of these being identified in all of them (betonicine, betaine, trigonelline and choline); betonicine was the predominant compound in a concentration range of 264 to 52384 mg/kg. It was possible to statistically assign over 50 % of the samples to the corresponding apiary of origin, the best results being obtained for the Tío Natalio apiary (75 %); this classification was even better in the case of the harvest period, as more than 75 % of the samples were correctly assigned, and in two periods (April-May and June) a 90 % rate was obtained.