Quantification of lactic acid in wines using an amperometric biosensor

The objective of this study was to develop an analytical method that allows for the rapid and cost-effective detection and quantification of lactic acid in wines. The analysis of lactic acid is a time-consuming and costly process in the food industry. Therefore, the use of an enzymatic amperometric sensor that employs lactate oxidase (LacOx) immobilized on an oxygen electrode enabled the determination of lactic acid in wine. This study utilizes a voltage of -500mV and recorded the amperometric signal was obtained during oxygen consumption while lactic acid oxidation occurred in the sensor reactor. The detection time was at 10 s. A positive linear relationship was obtained between oxygen consumed as a function of time (mg O2/L x s-1). The lactic acid concentration ranged from 1 to 7 mM with a coefficient R2 = 0.994. The sensor exhibited good specificity KM = 0.675. The immobilized enzyme retained over 85% activity for 60 days, allowing for the reuse of the previously modified membrane up to 22 times. In comparison to other methods documented in the literature, the results demonstrate a favourable analytical quality. Furthermore, other aspects, such as the low residual formation, also exhibit a positive outcome. The analysis of lactic acid showed good correlation when compared to HPLC methodology, which occupies the same linear range. This validates the use of the sensor as an alternative method for quantifying lactic acid in wine. The value of this study lies in its presentation of a technique that is more straightforward to implement than traditional methods for quantifying lactic acid in grape wines.