Quality control of oral herbal products by an electronic tongue—Case study on sage lozenges

Quality control of complex herbal extracts remains a challenge for analytical procedures as only representative ingredients can be characterized, but not the whole extract. A promising alternative are electronic tongues which are, due to sensors’ non-specificity, able to globally characterize complex mixtures. This article elaborates the application of an electronic tongue as an alternative method in quality control of herbal lozenges as a case study. The Insent taste sensing system SA402B was used equipped with 7 sensors imitating the taste stimuli and sensory signals umami, saltiness, astringency, bitterness and sourness. The results were compared to well-established analytical procedures like high performance liquid chromatography and gas chromatography. Further, a human taste panel (n = 13) was used as reference method.A measurement protocol was developed for quality control and validated according to ICH guideline Q2. The validation showed that all sensors could be used. After measuring different samples, especially the sensors for saltiness and astringency showed adequate results in comparison to the HPLC and GC analysis. Two samples were found to have different taste properties which could be confirmed by low cineol content determined by gas chromatography. In comparison to human taste assessment the electronic tongue was more sensitive to distinguish between specified and outlying taste. Data evaluation based on univariate statistics as well as multivariate could be used to detect the differing samples. Therefore, the Insent taste sensing system seems to be a promising analytical tool for quality control of complex herbal mixtures.