Comparative study of physiochemical properties in Iranian multi-floral honeys: Local vs. commercial varieties

Abstract

Iran, a leading honey-producing country, faces challenges in honey exports. This study aimed to evaluate the melissopalynological and physicochemical characteristics of local honeys belonging to Iranian flora, and compare them with Iranian commercial honeys. For this purpose, seven local honey samples were collected from Iran's renowned floristic regions, alongside seven commercial multi-floral honeys from a supermarket. Moisture content (MC), total solids (TS), pH, free acidity (FA), ash, electrical conductivity (EC), sugar profile, hydroxymethyl furfural (HMF), diastase number (DN), and proline were assessed. The sugar profile was analyzed by high-performance liquid chromatography with a refractive index detector (HPLC-RID). Pollen analysis classified local honeys as multi-floral. The results revealed that MC, TS, pH, FA, ash, and EC values in both local and commercial samples conformed to approved standards (Codex Alimentarius and European Union). Two local and one commercial sample exclusively satisfied the sucrose standard level. Of the local honeys, two samples complied with HMF standard, while five fulfilled DN criterion, and four had proline values within acceptable ranges. Conversely, HMF (56.32-228.11 mg/kg), DN (3.13-7.22 Schade units/g), and proline (109.84-173.86 mg/kg) levels in all commercial samples failed to meet the standard. A significant correlation was found between ash and EC (r = 0.915, p < 0.01) in local honeys, whereas no strong correlation (r = 0.299) existed in commercial samples. Hierarchical cluster analysis confirmed that Iranian honeys lacked clustering by botanical origin, possibly due to extensive sugar adulteration or thermal treatment. Overall, study findings confirmed the significantly inferior quality of Iranian commercial honeys compared to local varieties, albeit some local samples also exhibited quality concerns. Accordingly, it is recommended that regulatory bodies provide periodic training for beekeepers and establish monitoring programs to enhance honey quality, thereby boosting Iran's share in the global honey export market.

Keywords: Cluster analysis; HPLC-RID; Hydroxymethyl furfural; Iranian honeys; Physicochemical properties.

Fig. 1

Map of Iran indicating the regions where local multi-floral honey samples were collected.

Fig. 2

Relative abundance of the most common pollen families found in the Iranian flora.

Fig. 3

Pearson's correlation matrix heat-map between investigated parameters. (a) Local Iranian honeys, and (b) commercial Iranian honeys. In the right-hand figure, the melibiose and melizitose parameters were excluded from the correlation plot analysis due to their absence in any of the commercial samples. The color scale on the right side of each figure denotes the correlation coefficients, ranging from +1 (complete direct covariations) to 0 (without covariations) and to −1 (complete inverse covariations).

Fig. 4

The Z-score heat-map with two-dimensional dendrograms for classification of the investigated variables and honey samples using the Ward's method. The color key represents the scaled values of physicochemical parameters, with the yellow spectrum corresponding to low levels, and the red spectrum corresponding to high levels.