Physicochemical and nutritional profiles of stingless bee (Meliponula bocandei) products from the Western highlands and Lake Victoria crescent agro-ecological zones

Abstract

Several communities in tropical and subtropical regions of the world have exploited stingless bee products for centuries. In other countries, the physicochemical and nutritional properties of these products have been determined. In spite of the long-term exploitation of these products by local communities in Uganda, their properties remain undetermined. Nonetheless, an understanding of the physicochemical and nutritional profiles of stingless bee products such as honey, pollen and propolis is important for developing baseline standards for quality assurance and for identifying sources of stingless bee products in the market. In this study, stingless bee (Meliponula bocandei) honey, pollen and propolis were collected during wet (October, 2020) and dry (February, 2021) seasons from the Western Highlands and Lake Victoria crescent agro-ecological zones of Uganda. Samples were analysed for moisture content, water activity, pH, ash content, viscosity, antioxidant properties, HMF, electrical conductivity and mineral elements. Antioxidants such as DPPH, total phenolic compounds and total flavonoids were found in all the products in both the Western highlands and Lake Victoria Crescent ago-ecological zones and the two season. Zinc was only detected in pollen and propolis while iron (Fe) was detected in honey and propolis in the two agro-ecological zones. Results show that all the three products had significantly higher amounts of phenols, flavonoids and DPPH during the dry season than in wet season in both agro-ecological zones. Of all the three products, honey had the highest moisture content (26.4±1.4 g/100g) and the lowest water activity (0.7±0.03%). The mean HMF of stingless bee honey (5.4±4.7 mg/kg) was lower than the acceptable maximum limit of 40 mg/kg in the stingless bee honey draft East African Community and European Union standards. It was also observed that propolis had the highest levels of the antioxidant properties: DPPH (40±53%), flavonoids (111±124 gGAE/100g) and phenols (160±199 gCEQ/100g). Propolis also had the highest concentration of macro (Ca, P, K, Mg and Mn) and micro (Fe, Cu and Zn) minerals. This study revealed that stingless bee honey is of high quality because of its low mean HMF despite its origin in the hot equatorial region. Generally, the studied stingless bee products meet international quality standards. However, to ensure safety of the stingless bees products, there is need to specifically pinpoint the source (s) of heavy metal contaminants, specifically in the areas from where the bees forage.