Influence of botanical origin, processing techniques, and adulteration on the physicochemical and optical properties of honey from Northern Malawi

This study evaluated the influence of botanical origin, processing technique, and brown sugar syrup adulteration on the physicochemical and optical properties of honey from Northern Malawi, while assessing the suitability of conventional quality parameters for detecting adulteration. Eight authentic honey samples were procured from four botanical origins (natural vegetation, pine forest, coffee plantation, and macadamia plantation), processed using cold and thermal processes, and adulterated with brown sugar syrup at 0, 10, 30, and 50% (v/v). A 4 × 2 × 4 factorial experiment generated 32 treatment combinations with three replicates (96 determinations). Moisture content, electrical conductivity (EC), viscosity, density, °Brix, and colour (L*, a*, b*, hue) were determined using standard methods. Three-way ANOVA, Pearson correlation, and PCA were performed. Botanical origin, processing technique, and adulteration significantly (p < 0.05) affected all measured properties. Increasing adulteration increased moisture, EC, lightness, and yellowness while reducing viscosity, density, °Brix, and redness. Strong correlations were observed between adulteration and moisture (r = 0.99), EC (r = 0.99), and viscosity (r = −0.98). PCA explained 95.1% of total variation and clearly separated authentic from adulterated honey. These findings demonstrate that conventional physicochemical and optical measurements provide reliable, low-cost complementary indicators for honey authentication in Malawi.