Development of a sensor to quantify lactic acid in beer

The determination of lactic acid in beer is a crucial quality parameter.Increase the product's shelf life and hinders the growth of spoilage bacteria such as salmonella. The analysis of this parameter is indispensable in production lines and the use of a biosensor could potentially simplify the process. An enzymatic sensor utilizing lactate oxidase (LacOx) was optimized for determining lactic acid content in beer. The sensor immobilized the enzyme with an oxygen electrode. LacOx from Pediococcus sp was used in this study, with a voltage of −600 mV. An amperometric signal was obtained, and the signal was recorded at 5 s due to oxygen depletion during lactic acid oxidation. The reaction rate was then correlated to the lactic acid content. A linear relationship was found between consumed as a function of time (mg O2/L x s) and lactic acid concentration in the range of 10 and 2700 µM, with a coefficient of determination of R2 = 0.9947. The immobilized enzyme sensor showed a high sensitivity of 0.01 mM and was stable enough to allow the reutilization of the membranes up to 25 times without loss of activity, were 90 % of its initial activity remained after for 50 days. This system showed good specificity (KM = 450 µM). The correlation, validated through the use of the same linear range using reference method High -performance liquid chromatography (HPLC), establishes that is viable alternative to quantify lactic acid in various beer types.