Table 1.

Selected works dealing about the characterization, classification and authentication of food products with voltammetric electronic tongues.

Food Product	Working Electrodes	Data Analysis	Comments	Ref.
Orange juice and milk	Pt and Au	PCA	First voltammetric e-tongue	[14]
Milk	Au, Pt, Rh, stainless steel	PCA	Monitoring of milk in dairy industry	[28]
	Au, Cu, Au modified with Prussian blue	PCA	Recognition of milk adulteration with hydrogen peroxide	[29]
	Au, Cu, Pt	PCA	Recognition of milk adulteration with urea, formaldehyde and melamine	[30]
	Au, Pd, Pt	MPCA, NPLS-DA	Recognition of milk adulteration with urea	[31]
	Au, Pt, Ag	PCA, PLS-DA	Discrimination of various brands of pure milk	[32]
	Au, Ag, Pt, Pd	PCA, CA	Monitoring of quality and storage time of unsealed pasteurized milk	[15]
Yogurt	Au, Ag, Pt, Pd	SVM	Monitoring the fermentation, post-ripeness and storage processes of set yogurts	[33]
	Au, Ag, Pt, Pd	PCA, CA	Evaluation of varieties of set yogurts	[34]
Wines and liqueurs	Phthalocyanine-based carbon paste electrodes and electrodes covered with conducting polypyrrole doped with different counter ions	PCA	Detection of adulterations in wines	[16]
	Au, Cu	PCA	Discrimination of wines and whiskies of different quality	[35]
	Au, Ag, Pt, Pd, W, Ti	PCA, CA	Classification of rice wines of different ages	[36]
	Five bulk-modified graphite-epoxy electrodes	PCA, ANN	Cava wine authentication	[37]
	Six bulk-modified graphite-epoxy electrodes	LDA	Cava wine authentication	[17]
	Five different graphite-epoxy composite electrodes	PCA, ANN	Discrimination of wines of different types and PDO	[38]
	Sensors based on metallic and bulk-modified graphite electrodes	LDA	Classification of wines of different PDO	[39]
	Four carbon paste electrodes chemically modified in different ways	PCA	Discrimination between red wines aged in oak barrels and matured in steel tanks in contact with oak wood chips	[40]
	Three nanocomposites modified electrodes prepared with Au and Cu nanoparticles in the presence of conducting polymers and carbon nanotubes.	PCA, LDA	Classification of rice wines of different geographical origins	[41]
	Six modified epoxy-composite electrodes	LDA	Classification of brandies according to their taste category and ageing method	[42]
	Four carbon paste electrodes: one unmodified and the others chemically modified with Co, Fe and Zn phthalocyanines	PCA	Discrimination of apple liqueurs	[43]
Grapes	Eight metallic electrodes housed inside a stainless steel cylinder	PCA	Study of grape ripening	[44]
	Poly-ethylendioxythiophene modified Pt electrode and sonogel carbon electrode	PCA	Study of grape ripening	[45]
Beer	Three enzymatic biosensors based on tyrosinase and phthalocyanines as mediators	PCA, LDA	Monitoring of the aging of beers	[46]
	Six bulk-modified graphite-epoxy electrodes	PCA, LDA, PLS-DA	Classification of three types of beer: Lager, Stout and IPA	[47]
	Four commercial screen-printed electrodes made of carbon, Au, carbon/Co-Phtahlocyanine and Pt	PCA, LDA	Classification of different types of beer	[48]
Coffee	Six graphite-epoxy electrodes modified in different ways	LDA, SVM	Geographical classification of Mexican coffees	[49]
	Au wire and graphite rod	PCA	Discrimination of civet coffee	[50]
Tea	Ir, Pt, Rh	PCA	Discrimination of nine different teas	[51]
	Au, Ir, Pd, Pt, Rh	PCA, LDA	Tea quality assessment	[52,53]
	Pt and glassy C	PCA, LDA	Classification of black tea liquor	[54]
	Metallic oxide-modified nickel foam electrodes (SnO2, ZnO, TiO2, Bi2O3)	PCA, SVM	Classification of green and black teas	[55]
	Au, Ir, Pd, Pt, Rh	PCA	Monitoring the fermentation process of black tea	[56,57]
Honey	Au, Ag, Pt, Pd, W, Ti	PCA, CA, DFA	Classification of mono-floral honeys	[58]
	Au, Ag, Pt, Pd, W, Ti	PCA, DFA	Tracing floral and geographical origins of honey	[59]
	Pt, Au, glassy C, Ag, Pd, Ni, Cu	PCA, SVM, HCA	Classification of Moroccan and French honeys according to geographical and botanical origins and detection of adulteration	[60,61]
	Au, Ag, Pt	PCA, LDA	Authentication of mono-floral and honeydew Romanian honeys	[62]
	Ir, Rh, Pt, Au	PCA	Monitoring honey adulteration with sugar syrups	[63]
	Au, Ag, Pt, glass electrode	PLS-DA	Monitoring honey adulteration	[64]
Oil	Six electrodes based on polypyrrole	PCA, PLS-DA	Discrimination of extra virgin olive oils according to their degree of bitterness	[65]
	Pt, Au, glassy C, Ag, Ni, Pd, Cu	PCA, DFA, SVM	Detection of adulteration in argan oil	[66]
	Modified carbon paste electrodes	PLS-DA	Detection of virgin olive oil adulteration	[67]
	Cu, glassy C, Au, Ni, Pd, Pt, Ag	PCA, SVM, HCA	Identification of Portuguese olive oils	[68]
Meat and fish	Screen-printed electrodes modified with bisphthalocyanine and polypyrrole	PCA, PLS-DA	Beef freshness monitoring by detection of ammonia and putrescine	[69]
	Pt, Au, Ag, glassy C, Pd, Cu, Ni	PCA	Assessment the origins of red meats and their storage time	[70]
	Ir, Rh, Pt, Au, Ag, Co, Cu, Ni	PCA	Shelf-life assessment of fresh cod in cold storage	[71]