The Addition of Acacia Honey to Kefir Results in Changes to Physicochemical and Microbiological Properties

Abstract

This study aimed to evaluate the impact of adding acacia honey on the physicochemical and microbiological properties of cow's milk kefir. The research was conducted from February to April 2025 at the Laboratory of Dairy Science and Technology at Universitas Brawijaya, employing a five-treatment experimental design with three replications: 0%, 2%, 4%, 6% and 8% honey concentrations. The milk was pasteurised at 70 °C, cooled to 40 °C, mixed with honey and inoculated with 5% kefir grains by weight. The mixture was then fermented for 24 hours at 27–28 °C. Increasing the honey concentration was found to slightly elevate the pH level (from 3.88 to 3.97), while significantly reducing the viscosity level (from 7.44 to 1.99 Pas). Total titratable acidity (TTA) increased at a honey concentration of 2% (1.94%), but decreased at higher concentrations. Microbiological analysis revealed that adding honey increased both lactic acid bacteria (LAB) and yeast populations to 6.89 and 6.08 log CFU/mL, respectively, at an 8% honey concentration. These values are close to the minimum threshold for probiotic functionality (≥7 log CFU/mL), suggesting that the product remains within an acceptable range for health benefits. While this study did not examine honey concentrations above 8% in detail, preliminary observations suggested that higher concentrations tend to disrupt the balance of microbes and negatively impact the texture and fermentation process. This results in excessive viscosity and unclear microbial interactions. Therefore, concentrations above 8% are not recommended without further investigation. These results suggest that acacia honey enhances microbial viability and modulates the fermentation process, thereby influencing the acidification and texture of the final kefir product. Consequently, acacia honey can be considered a functional ingredient for tailoring the nutritional and sensory qualities of kefir.