Table 2.

Studies reporting the use of near-infrared spectroscopy for the quantification of bioactive compounds in food products (2016–2020).

Food Matrix	Analyte(s)	Sample Size (cal/val)	Wavelength Range (nm)	Optical Geometry	Statistical Method	Test Set	Cross-Validation	R2CV	RMSECV	Notes	Reference
Fruit
Açaí and juçara	Total anthocyanin content	Variable (n = 374 total)	1606–1793	Reflectance	PLS	Independent populations R2p = 0.74–0.88; RMSEP = 5.09–6.76 g/kg	LOO	0.89–0.91	2.50–2.91 (g/kg)	Fruit from two seasons and four localities	[98]
Bilberry (dried powder)	Anthocyanins	38/27	1064–1640, 1833–2354	Reflectance	PLS	Dependent test set (randomly selected samples)	LOO	0.995	0.28 (% w/w)	NIR analysis could identify counterfeit bilberry samples	[99]
Blackberry	Total phenolics Total carotenoids	90/30	400–2500	Reflectance	PLS	None	n/s	0.69 0.76	1.69 0.95 (mg/g)		[100]
Grapes (red)	Trans-resveratrol Quercetin Total phenols	15	900–1700	Reflectance	PLS	None	LOO	0.988 0.955 0.974	0.424 mg/kg 0.008 mg/kg 12.15 mmol/kg	Three locations; two seasons	[101]
Grapes (red and white)	Total phenolics	203/67	400–1100 900–2500	Reflectance	PLS, SVM	Dependent test population	n/s	0.872–0.914 0.697–0.726	0.15–0.22 0.28–0.31 (mg/g)	Two cultivars from one season and location; SVM gave better results than PLS	[102]
Grapes (red)	Total anthocyanins Total 3-O-glucoside anthocyanins Total 3-O-(6-acetyl)glucoside anthocyanins Total 3-O-(6-p-coumaroyl)glucoside anthocyanins Malvidin 3-O-glucoside Malvidin 3-O-(6-acetyl)glucoside Malvidin 3-O-(6-p-coumaroyl)glucoside Petunidin 3-O-glucoside Petunidin 3-O-(6-acetyl)glucoside Petunidin 3-O-(6-p-coumaroyl)glucoside Delphinidin 3-O-glucoside Delphinidin 3-O-(6-acetyl)glucoside Delphinidin 3-O-(6-p-coumaroyl) glucoside Peonidin 3-O-glucoside Peonidin 3-O-(6-acetyl)glucoside Peonidin 3-O-(6-p-coumaroyl)glucoside Cyanidin 3-O-glucoside Cyanidin 3-O-(6-acetyl)glucoside Cyanidin 3-O-(6-p-coumaroyl)glucoside	60/20	380–1028	Reflectance (hyperspectral imaging)	MPLS	Dependent test set (stratified samples)	Six-fold cross-validation	0.91 0.92 0.90 0.83 0.87 0.90 0.80 0.93 0.57 0.91 0.91 0.92 0.88 0.80 0.75 0.88 0.77 0.86	189.05 155.94 4.12 23.09 73.93 4.13 13.32 29.44 0.98 2.04 48.41 3.28 30.35 0.31 3.81 16.43 0.16 1.78 (mg/L)	Eight different cultivars from two sites	[103]
Grapes (red)	Nonacylated anthocyanins Total anthocyanins	47/-	950–1650	Reflectance (hyperspectral imaging of single grapes)	PLS	Dependent test population	LOO	0.72 0.72	0.78 0.70 (mg/grape)	Fruit from two dates and two vineyards within one season	[104]
Grape pomace (marc)	Catechin Epicatechin Proanthocyanidin B1 Proanthocyanidin B2 Proanthocyanidin B3 Proanthocyanidin B4 Proanthocyanidin trimer 1 Proanthocyanidin trimer 2 Proanthocyanidin tetramer 1 Proanthocyanidin tetramer 2 Proanthcyanidin B2-3-O-gallate Galloyl proanthocyanidin Total flavanols Gallic acid Protocatechuic acid Caffeic acid Caftaric acid Cis-coutaric acid Trans-coutaric acid Total phenolic acids Quercetin 3-O-rutinoside Quercetin 3-O-glucuronide Quercetin 3-O-glucoside Quercetin pentoside Kaempferol 3-O-galactoside Kaempferol 3-O-glucuronide Kaempferol 3-O-glucoside Quercetin Kaempferol Total flavonols	12/-	950–1650	Reflectance (hyperspectral imaging)	PLS	None	LOO	0.80 0.96 0.65 0.75 0.50 0.63 0.65 0.86 0.65 0.53 0.89 0.58 0.78 0.75 0.82 0.92 0.91 0.83 0.95 0.87 0.63 0.81 0.64 0.15 0.98 0.93 0.98 0.72 0.97 0.70	14.00 4.72 20.53 1.86 3.43 3.01 3.12 7.68 11.62 2.66 6.29 7.27 66.63 5.58 2.70 0.36 2.56 0.15 0.19 9.61 1.82 4.36 5.95 0.04 0.11 0.07 0.41 0.19 0.02 14.27 (mg/100 g)	Fruit from one variety, season and location	[105]
Grape skins (red)	Total iron-reactive phenolics Anthocyanins Tannins	40/20	977–1625	Reflectance (hyperspectral imaging)	PCR, PLS, SVR	Dependent test set	Segment validation	0.907 0.879 0.896	0.178 0.144 0.107 (mg/L)	Five cultivars from four dates in one growing season	[106]
Grape seeds (red)	Total iron-reactive phenolics Tannins	40/20	977–1625	Reflectance (hyperspectral imaging)	PCR, PLS, SVR	Dependent test set	Segment validation	0.879 0.924	0.240 0.519 (mg/L)	Five cultivars from four dates in one growing season	[106]
Guava (frozen pulp)	Ascorbic acid	50	1000–1892, 2007–2227	Transflectance	PLS	Dependent test set (randomly selected samples)	LOO	0.85	6.14 mg/100 g (test set)	Samples from two Brazilian marketplaces	[107]
Jujube	Gallic acid Caffeic acid L-epicatechin Phloridzin Cianidanol	52/26	900–1700	Transmittance	Si-ACO-PLS	Dependent test population	n/s	0.879 0.887 0.906 0.858 0.836	3.06 6.04 16.30 0.84 16.01 (µg/g)	Samples from five regions	[108]
Kakadu plum (powder)	Ascorbic acid	80/5	866–2532	Diffuse reflectance	PLS	Independent (commercially sourced samples) R2p = 0.73; RMSEP = 4733 mg/100 g	n/s	0.93	1839 mg/100 g		[109]
Marsh grapefruit	β-Carotene Total carotenoids	240	850–2500 400–850	Reflectance	PLS	Independent (samples from a separate orchard)	Test set validation	0.99 0.92 (test set)	0.00 2.69 (µg/g) (test set)	Fruit from one season and two locations	[13]
Raspberries	Total phenols Total anthocyanins TAC (FRAP)	168	950–1650	Reflectance (hyperspectral imaging)	PLS	None	n/s	0.70 0.63 0.61	127 12 39 (mg/100 g)		[110]
Tomato	Total phenolics Lycopene Total flavonoid β-Carotene	50	285–1200	Reflectance	PLS	None	LOO?	0.834 0.864 0.790 0.708	1.80 1.03 1.82 1.14 (µg/g)		[111]
Tomato	Lycopene β-Carotene	180/60	500–1100	Transmittance	PLS	Semi-independent (separate harvest in same season) R2p = 0.85, 0.77; RMSEP = 1.79, 1.00 mg/kg	LOO	0.89 0.88	1.56 0.63 (mg/kg)		[112]
Tomato (dehydrated and ground)	Lycopene Phenols TAC (DPPH) TAC (FRAP) TAC (ABTS)	61/31	800–2500	Reflectance	PLS, RBF-NN	Dependent test set	n/s	0.882 0.910 0.882 0.876 0.937	1.61 80 0.70 0.97 0.86 (mg/100 g)	RBF-NN generally performed better than PLS regression	[113]
Wax jambu	Total phenolics Total anthocyanins	50/35	1000–2400	Diffuse reflectance	PLS	Dependent test set (Kennard-Stone selection)	n/s	0.94 0.98	22.18 9.0 (mg/100 g)		[114]
Vegetables
Carrot	Ascorbic acid β-Carotene	24/6?	420–1100	Reflectance	PLS	Dependent test set	Four-fold cross-validation	0.98 0.98	0.04 µg/g 0.10 µg/100 g	Roots sampled over an 8-week storage period	[115]
Red cabbage (EtOH extract)	Total anthocyanins Monomeric anthocyanins Total polyphenols	1 (with 33 serial dilutions)	1000–2500	Transmittance	PLS	9 dilutions prepared from new cabbage extract	Segment validation	0.98 0.98 0.96	16.4 mg/L 20.2 mg/L 42.7 mg/L		[116]
Potato	Total phenolics Antioxidant capacity (DPPH)	160/68	1100–2300	Reflectance	PLS	Dependent test set	Venetian blind cross-validation	0.84 0.67	1.20 1.21 (mg/g)	Included white, red, yellow and purple-fleshed cultivars	[117]
Grains/pulses
Barley malt	Total phenolics	10	1000–2500	Reflectance (hyperspectral imaging)	SVM, SVR	Dependent test set (5% of total pixels)	n/s	0.85	1 ppm		[118]
Buckwheat, oat, millet	Total phenolics	77	1596–2396 1128–2162 740–1070	Reflectance	PLS	Test set used but no information provided on its origins or size	LOO (for most models)	0.921 0.951 0.823	1.46 1.11 1.98 (mg/g)	Compared three handheld instruments (microPhazir RX, MicroNIR 2200, SCiO)	[119]
Common bean (flour)	Total phenols Ortho-diphenols Flavonoids Gallic acid Catechin Myricetin-3-glucoside Quercetin-3-6″-manolyl-glucoside Kaempferol-3-glucoside Kaempferol-3-6″-manolyl-glucoside Kaempferol	42/-	1000–2500	Reflectance	PLS	Spectra randomly selected from dataset (1/3 of total spectra)	LOO	0.91 0.85 0.90 0.96 0.48 0.97 0.90 0.85 0.93 0.87	RPDs: 5.20 4.84 5.18 10.25 2.38 10.25 7.52 6.27 9.32 6.51	21 varieties; two seasons	[120]
Mungbean	Catechin Chlorogenic acid Caffeic acid p-coumaric acid t-ferulic acid Vitexin Isovitexin Myricetin Quercetin Kaempferol	42/18	1600–2500	Reflectance (from whole grains)	PLS	Dependent test set	Segment validation	0.996 0.998 0.992 0.989 0.998 0.997 0.997 0.994 0.989 0.998	0.603 0.590 1.78 1.8 0.519 0.238 0.23 1.82 1.67 0.5 (%)		[121]
Quinoa (whole seed)	Total free phenolics Total betalains TAC (DPPH)	38/-	400–2500	Reflectance	PLS	None	Segment validation	n/s n/s 0.73	n/s n/s 8.6 (mmol/kg)	For TAC in ground seed; R2CV = 0.66; RMSECV = 9.6 mmol/kg	[122]
Soybean	Total anthocyanins Cyanidin-3-glucoside Delphinidin-3-glucoside	70	1000–2500	Reflectance	PLS	Subset of spectra of samples included in calibration set	n/s	0.88 0.90 0.88	0.13 0.12 0.03 (mg/g)		[123]
Oils
Olive oil	Squalene	118/59	1100–2300	Transmittance	PLS	Dependent test set	LOO?	0.83	2.31 (g/kg) (pred)	Poorer results obtained using Vis–NIRS data	[124]
Olive oil	Total tocopherols α-Tocopherol β-Tocopherol γ-Tocopherol	197/91 189/93 197/102 195/101	350–2500	Transmittance, transflectance	PLS	Dependent test set	LOO?	0.89 0.92 0.54 0.85	43.83 33.90 0.59 4.54 (mg/kg) (SEC)	Vis–NIRS gave slightly better results than NIRS in most cases	[125]
Olive oil	Tyrosol Tyrosol secoiridoids Hydroxytyrosol Hydroxytyrosol secoiridoids Total phenolics	75/18	800–2500	Transmittance	PLS	None	LOO	0.55 0.84 0.55 0.82 0.82	5.27 41.5 4.84 43.1 76.7 (mg/kg)		[126]
Olives (as paste)	Total phenolics Oleuropein	291/53 147/53	1400–2400	Reflectance	PLS	Dependent test set	LOO?	0.71 0.73 (cal)	0.08 6.6 (mg/kg)	Samples obtained across seven seasons	[127]
Aromatic plants
Black pepper (whole)	Piperine	132/-	950–1650	Reflectance	PLS	None	Segment validation	0.726	0.289g/100 g	For ground samples; R2CV = 0.850, RMSECV = 0.231g/100 g	[128]
Black tea	Caffeine Epigallocatechin gallate	37/19	950–1650	Reflectance	PLS, MLR	Dependent test set	LOO?	0.933 0.782	3.65 3.32 (mg/g)		[129]
Black tea	Cianidanol Ferulic acid Gallic acid Rutin Phloridzin L-epicatechin	84/56 (20 replicate samples at seven time points)	899–1724	Transmittance	CARS-PLS	Dependent test set	n/s	0.956 0.928 0.911 0.825 0.881 0.969	9.66 0.21 4.22 0.77 6.85 20.1 (mg/100 g)	20 tea samples collected at seven time points during fermentation process	[130]
Cocoa bean	Total phenols Catechin Epicatechin Epigallocatechin Theobromine	74/- 76/- 75/- 72/- 75/-	400–2498	Reflectance	PLS	None	LOO?	0.71 0.62 0.04 0.02 0.77	6.09 0.65 5.24 0.09 4.55 (mg/g)		[131]
Cocoa bean	Total polyphenols	72	800–2778	Diffuse reflectance	PLS	None	LOO	0.84	0.93 (mg/g)	Sample variation induced by different periods of storage and fermentation	[132]
Cocoa bean husk	Total phenols Catechin Epicatechin Epigallocatechin Theobromine	77/- 80/- 79/- 78/- 78/-	400–2498	Reflectance	PLS	None	LOO?	0.81 0.74 0.06 0.20 0.83	4.75 0.55 5.31 0.10 3.72 (mg/g)		[131]
Coffee bean	Chlorogenic acid Total phenolics	101/36	950–1650	Reflectance (hyperspectral imaging)	MPLS	Dependent test set	n/s	0.81 0.58 (cal)	0.91 4.63 (mg/g) SEP = 15.6 and 17.6%		[133]
Ginger	Zingerone 6-Gingerol 8-Gingerol 10-Gingerol 6-Shogaol	58/22	1389–2500	Reflectance	PLS	Dependent test set	LOO	0.981 0.986 0.988 0.997 0.998 (cal)	0.076 0.072 0.078 0.077 0.084 (mg/g)		[134]
Beverages
Cashew apple nectar	Ascorbic acid	49/16	1000–1903, 1971–2227	Transflectance	PLS	Dependent test set (randomly selected samples)	n/s	0.84 (cal)	4.8 mg/100 g (test set)	Samples from two Brazilian marketplaces	[135]
Coffee aqueous solution	Chlorogenic acid	86	401–1871	Transmittance (1 mm path length)	PLS	None	LOO	0.556	0.76 mg/mL	Key predictor wavelength was around 1450 nm (C-H vibration; second overtone)	[136]
Grape juice	Total phenolics Anthocyanins	49/16	1000–2500	Transflectance	PLS	Dependent test set (randomly selected samples)	Optimising no. of latent variables	0.96 0.84 (cal)	37 4.44 (mg/100 mL) (test set)	Slightly worse results for phenolic content compared to MIR	[137]
Guava nectar	Ascorbic acid	41/13	1000–1899, 1983–2227	Transflectance	PLS	Dependent test set (randomly selected samples)	n/s (LOO?)	0.86 (cal)	7.44 mg/100 g (test set)	Samples from two Brazilian marketplaces	[135]
Soft drink (grape and passionfruit)	Ascorbic acid	~47/20	1000–2500	Reflectance	PLS	Test set of 5 samples created by diluting one sample to specific concentrations	LOO	0.70 0.76	0.67 0.56 mg/g		[138]
Wine (red)	Trans-resveratrol Quercetin Total phenols	20	900–1700	Transmittance	PLS	None	LOO	0.994 0.990 0.996	0.113 mg/L 0.073 mg/L 0.144 mM	Three locations; two seasons	[101]
Wine (red)	Gallic acid Catechin B1 (flavonol dimer) Polymeric phenols Caftaric acid Caffeic acid Coutaric acid p-coumaric acid Quercetin-3-glucoside Quercetin Kaempherol Delphinidin-3-glucoside Cyanidin-3-glucoside Petunidin-3-glucoside Peonidin-3-glucoside Malvidin-3-glucoside Delphinidin-3-acetylglucoside Cyanidin-3-acetylglucoside Petunidin-3-acetylglucoside Peonidin-3-acetylglucoside Malvidin-3-acetylglucoside Delphinidin-3-cumarylglucoside Petunidin-3-cumarylglucoside Peonidin-3-cumarylglucoside Malvidin-3-cumarylglucoside Polymeric pigments MCP tannins Anthocyanins	~387/182	800–2500	Transmittance	PLS using PRESS	Dependent test set	Segment validation	0.86 0.83 0.76 0.88 0.86 0.87 0.84 0.87 0.88 0.84 0.85 0.92 0.86 0.9 0.85 0.87 0.88 0.91 0.92 0.91 0.85 0.86 0.85 0.86 0.84 0.86 0.92 0.87	3.01 5.85 4.94 135 8.8 0.82 2.63 0.61 10.3 1.65 0.15 2.32 0.05 2.16 1.73 16.5 0.65 0.34 0.89 0.65 7.15 0.19 0.57 0.84 4.27 5.71 204 53.1 (mg/L)	Wines comprised four cultivars from 13 vinifications over two seasons; more accurate at predicting phenolic content than ATR-MIR or transmission FT-IR.	[92]
Other foods
Honey	Phenolics Flavonoids Carotenoids Antioxidants (FRAP)	105/45	1000–2500	Reflectance	PLS	Dependent test set (randomly selected samples)	Segment validation	0.884 0.903 0.922 0.922	14.5 1.01 0.035 0.43 (mg/100 g)	Six different floral varieties of honey	[139]
Propolis	Flavones and flavonols Flavanones and dihydroflavonols Antioxidant capacity (ABTS)	70/29	1100–2000	Reflectance (fibre-optic) on ground sample	MPLS	Dependent test set (randomly selected samples)	Segment validation	0.63 0.68 0.87 (cal)	29.4 9.5 112 (mg/g)	Samples sourced from Chile and Spain	[140]

Abbreviations: RBF-NN = radial basis function neutral network; LOO = leave-one-out cross-validation; n/s = not specified; PLS = partial least squares; SVM = support vector machine; TAC = total antioxidant capacity.