Homemade water kefir: Characterisation and first evidence of an effect on breath alcohol testing

Water kefir is a traditional fermented beverage that is increasingly consumed worldwide. The drink may contain varying levels of ethanol, and the impact of its consumption on the breathalyser is still unknown. Since many countries have established regulations on the levels of alcohol permitted in drivers, this study aimed to assess the effect of water kefir intake on the results of breath alcohol tests. Water kefir was prepared under four different conditions: 4% and 6% (w/v) of brown sugar, with or without 10% (v/v) of lemon juice. Chemical analysis (pH, organic acids, ethanol and saccharose) and microbiological counts (lactic acid bacteria, acetic acid bacteria, and yeasts and moulds) were performed at the beginning and after 24 and 48 h of fermentation. The condition that resulted in the highest ethanol production was used to produce water kefir for a breath alcohol test. Finally, two assays were conducted: 16 and 12 adult individuals drank 150 mL and 300 mL, respectively, of water kefir, and the concentration of breath alcohol was quantified using a breathalyser. The water kefir used had a pH value of 3.30 and a level of 2.17±0.08 g/100 mL of ethanol. In the first breath alcohol test, 16 participants were offered 150 mL of water kefir. None of them resulted positive to the breath alcohol test when performed after 30, 60, 90 or 120 minutes from ingestion. In the second assay, 13 participants were offered 300 mL of the same water kefir. Only one participant tested negative at all time points assessed. For the rest of the participants, breath alcohol tests were positive from min 10, peaking at min 30, and became negative after 75 min of the intake. Even with rather limited data, it is possible to conclude that water kefir intake may render positive a breath alcohol test, depending on the volume and ethanol content of the kefir consumed, as well as on other variables such as the BMI (Body Mass Index) of the consumer.