Effect of eucalyptus ash on microbial flora and aflatoxins in red sorghum malts and on physico-chemical and organoleptic characteristics of Ikigage beer

Abstract

Ikigage is a traditional Rwandan beer brewed primarily from red sorghum. However, its quality and safety can be compromised by microbial contamination and aflatoxin accumulation during production. These issues not only threaten public health due to the toxicity and carcinogenic nature of aflatoxins but also compromise the safety, sensory quality, and economic viability of traditional beverages. Current solutions to reduce these contaminants are often costly and unsuitable for small-scale, artisanal brewers. While traditional brewing practices have been studied, limited research exists on the potential of eucalyptus ash as a natural additive to improve microbial safety and extend shelf life. This study aimed to evaluate the effect of eucalyptus ash on the microbial flora, physico-chemical characteristics, aflatoxin content, and organoleptic properties of Ikigage beer. Red sorghum grains were malted with and without 5% eucalyptus ash and used to produce beers fermented with S-33 and LA-01 yeast strains in a controlled microbrewery. Sorghum samples were analyzed for microbial counts (total viable count, yeasts and molds) and Total aflatoxin while Ikigage samples were analyzed for physico-chemical parameters (pH, Turbidity, Total polyphenols, Total flavonoids, FAN, alcohol content) and organoleptic characteristics. Statistical analysis was conducted using ANOVA, and mean comparisons were performed at a 95% confidence level (p < 0.05). Results showed that eucalyptus ash addition significantly reduced total aflatoxin levels from 30.58 µg/kg for untreated sorghum to 0.47 µg/kg for sorghum treated with 5% ash. Physico-chemical changes included an increase in pH from 4.1 for Ikigage produced from son treated sorghum (SMNC) to 4.7 of Ikigage produced from sorghum treated with 5% ash, with a corresponding decrease in turbidity while rganoleptic evaluation indicated no adverse impact on taste, aroma, or consumer acceptability. The findings suggest that eucalyptus ash is a viable, low-cost solution to improve the safety and quality of Ikigage beer, aligning with public health priorities and supporting the modernization of traditional Rwandan brewing methods