ELECTRONIC TONGUE DISTINGUISHES ONIONS AND SHALLOTS

Onion and Jersey shallot belong to the same species (Allium cepa), but are from two different groups: A. cepa group cepa and A. cepa group aggregatum. Grey shallot belongs to another species, Allium oschaninii. Onions are seed-propagated, whereas shallots are vegetatively multiplied. Onions and shallots differ in taste, however, both contain sulphur organic compounds making sensory evaluation difficult. There is a practical need to reliably discriminate onion from shallot. The aim of this study was to apply the electronic tongue (e-tongue) in the classification of several cultivars of onions and shallots. The e-tongue is an analytical instrument, comprising an array of cross-sensitive chemical sensors and multivariate data processing tools. It has been previously and successfully applied in the classification, quantitative analysis and taste quantification of different beverages and foodstuffs. The sensor array comprised 21 potentiometric chemical sensors containing different active substances. Data processing was aimed at sample recognition and classification and was performed mainly by Principal Component Analysis (PCA). The e-tongue was capable of separating onions from shallots as well as detecting heterogeneous samples. Grey shallot was separated from all other tested material, a result which concurs with its botanical nature. The separation of onions and shallots could not be solely attributed to their respective dry matter content but to intrinsic features of their chemical composition, which e-tongue was able to detect.