Table 2.

Applications of isotope and elemental techniques in authenticity studies of fruit juices.

Aim of Study	Analytical Technique	Type of Study	Chemometric Approach	Sensitivity & Accuracy	Authenticity Markers	Ref.
Authentication of orange-based fruit juices - Identification of exogenous addition of water & sugar	ICP	Targeted	-	-	K, Ca, Brix value	[25]
Authentication of pomegranate juice – discrimination between homemade and commercial juices	ICP-OES	Targeted	ANOVA, Tukey’s test	-	Na, Ca	[30]
Authentication of orange juice – Geographical origin discrimination and detection of the adulteration with concentrate	IRMS	Targeted	DA	-	pulp δ2H, δ13C, δ15N, δ34S 87Sr/86Sr	[33]
Authentication of fruit juices - Differentiation according to geographical origin, botanical origin and determination of the addition of sugar	IRMS, SNIF-NMR	Targeted	PCA	Geographical origin prediction ability: 94%	(D/H)I, (D/H)II ethanol, δ13Cethanol, δ13Cpulp, δ13Csugars, δ18Owater	[34]
Authentication of apple juice - Differentiation according to geographical origin and cultivar	IRMS, NMR, ICP-MS, TXRF	Targeted	LDA	Geographical origin prediction ability: 83.9% Cultivar prediction ability: 75.8%	δ2H, δ18O water, δ15N, δ13C pulp, (D/H)I, (D/H)II ethanol, S, Cl, Fe, Cu, Zn, Sr	[35]
Quality evaluation and authentication of orange juice – Identification of exogenous addition of water & sugar	IRMS, ICP-MS,	Targeted	-	-	δ2H, δ13C, δ18O, Elemental profile	[37]
Authentication of Italian citrus juices – Evaluation of AIJN threshold limits	IRMS, SNIF-NMR	Targeted	ANOVA, PCA	-	(D/H)I, (D/H)II ethanol, δ13Cethanol, δ13Cpulp, δ13Csugars, δ18Owater, δ15Npulp, δ18Opulp	[38]
Authentication of fruit juices and wines – Identification of exogenous addition of water	IRMS	Targeted	-	-	δ18Owater, δ18Oethanol	[39]
Authentication of lemon juice – Identification of exogenous addition of acidifying agents & sugars	LC-IRMS	Targeted	-	Lowest level of detected adulteration: 10% for citric acid, glycose and fructose	Judgment Ratios: δ13C [Citric acid /Glucose], δ13C [Citric acid/Fructose], δ13C [Glucose/Fructose], δ13C [(Tartaric acid + Malic Acid)/2]	[41]
Authentication of lemon juice – Detection of the addition of organic acids & sugars	HPLC-co-IRMS	Targeted	Linear regression	-	δ13C of citric acid, glucose and fructose	[42]
Authentication of lemon juice – Differentiation according to geographical origin	ICP-MS	Targeted	LDA, PLS-DA, k-NN, RF, SVM	Correct classification rate: 76% (SVM) 71% (RF)	19 trace elements	[44]
Authentication of grape juice –Classification of organic and conventional juices	ICP-MS	Targeted	PCA, SIMCA	Prediction Ability: PCA: 55% SIMCA: 94% conventional samples, 100% organic	Ba, Ce, La, Mg, P, Pb, Rb, Sn, Ti, Na, Va	[46]
Authentication of grape juice –Differentiation between organic and conventional juices	ICP-MS	Targeted	SVM, MLP, CART,	Correct classification rate: 89.2% (SVM) 71% (CART, MLP)	Na, Sn, P, K, Sm and Nd	[47]
Authentication of orange and apple juices - Detection of the addition of sugars	Ion Chromatography – Carbohydrate Chromatography	Targeted	PCA	Correct classification rate: Apple juice: 94% Orange juice: 80%	K, Na, Mg, Ca, fructose, glucose, saccharose,	[48]
Authentication of pomegranate juice –Detection of juice-to-juice adulteration with peach and grape juice	AAS, AES	Targeted & Untargeted	-	K < 2000 mg L−1: indicative of adulteration	Ca, Mg, Fe, K	[49]

AAS: Atomic Absorption Spectrometry, AES: Atomic Emission Spectroscopy, ANOVA: Analysis Of Variance, CART: Classification And Regression Tree, DA: Discriminant Analysis, ICP-MS: Inductively coupled plasma mass spectrometry, IRMS: Isotope Ratio Mass Spectrometry, k-NN: k-Nearest Neighbors, LDA: Linear Discriminant Analysis, MLP: Multilayer Perceptron, PLS-DA: Partial Least Squares Discriminant Analysis, RF: Random Forest, SIMCA: Soft Independent Modelling by Class Analogy, SNIF: Site Specific Natural Isotope Fractionation, SVM: Support Vector Machine.