Characterization of Physicochemical Properties, Volatile Compounds, and Sensory Attributes of Tonto, a Traditional...

Tonto is a traditional Ugandan alcoholic beverage produced by spontaneous fermentation of banana juice. However, its chemical composition and sensory attributes have not been adequately studied. This study characterized the physicochemical properties, volatile compounds, and sensory attributes of Tonto (n = 42) produced in Ntungamo and Kalungu districts. During the 60 h fermentation, there was a significant (p < 0.05) decline in pH (4.9 ± 0.23-3.58 ± 0.32) and total soluble solids (15.01 ± 1.76-5.15 ± 0.74 °Brix), and a corresponding increase in acidity (0.21% ± 0.07%-0.77% ± 0.64%) and ethanol content (0.0-4.73 ± 1.05 %v/v). Thirty-eight volatile compounds, mainly esters and alcohols, were identified. Fruity and banana notes dominated in samples from Ntungamo, which also received higher acceptability due to high concentrations of ethyl and acetate esters known for fruity sensory attributes. Principal Component Analysis (PCA) further revealed that fruity esters correlated strongly with overall acceptability. Methanol concentrations varied widely (0-950.5 mg/L), with more than half of the samples, particularly those from Kalungu, exceeding the national safety limit (60 mg/L). These results demonstrate substantial variability in the quality and safety of traditionally produced Tonto and highlight the influence of regional differences in fermentation practices and raw material composition. The findings provide a scientific basis for improving and standardizing Tonto production through improved hygiene, controlled fermentation, process optimization, and starter culture development to enhance product quality and safety.