Table 3.
Studies reporting the use of mid-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/Presentation | Statistical Method | Test Set | Cross-Validation | R2CV | RMSECV | Notes | Reference |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Fruit | |||||||||||
| Kakadu plum (powder) | Ascorbic acid | 80/5 | 4000–400 | ATR | PLS | Independent (commercially sourced samples) R2p = 0.65; RMSEP = 2367 mg/100 g |
n/s | 0.91 | 1811 mg/100 g | [109] | |
| Vegetables | |||||||||||
| Red cabbage (EtOH extract) | Total anthocyanins Monomeric anthocyanins Total polyphenols |
1 (with 33 serial dilutions) | 4000–650 | ATR | PLS | 9 dilutions prepared from new cabbage extract | Segment validation | 0.98 0.98 0.96 |
18.1 mg/L 21.3 mg/L 44.4 mg/L |
[116] | |
| Grains/pulses | |||||||||||
| Buckwheat (leaves and flowers) | Rutin Quercetin Quercitrin Sum of flavonoids |
Not stated (total = 108) | 4000–500 | ATR (whole and ground dried samples) | PLS | Dependent test set | LOO | 0.99 0.99 0.95 0.98 |
3.63 0.06 2.48 4.80 (mg/g) |
Used seven different species of buckwheat | [141] |
| Common bean (flour) | Total phenols Ortho-diphenols Flavonoids Gallic acid Catechin Quercetin-3-glucoside Quercetin-3-6″-manolyl-glucoside Kaempferol-3-glucoside Myricetin Kaempferol-3-6″-manolyl-glucoside Kaempferol |
42/- | 4000–400 | ATR (flour) | PLS | Spectra randomly selected from dataset (1/3 of total spectra) | LOO | 0.86 0.31 0.86 0.94 0.89 0.43 0.73 0.38 0.35 0.39 0.84 |
RPDs: 4.36 1.54 4.30 10.12 9.47 1.91 4.25 1.23 1.81 1.79 7.03 |
[120] | |
| Soybean | Total anthocyanins Cyanidin-3-glucoside Delphinidin-3-glucoside |
70/- | 4000–650 | ATR (whole seeds) | PLS | Spectra of samples included in calibration set | n/s | 0.86 0.88 0.87 |
0.15 0.13 0.03 (mg/g) |
70 different varieties | [123] |
| Oils | |||||||||||
| Olive oil | Fatty acid methyl esters Fatty acid ethyl esters Fatty acid alkyl esters Diacylglycerols: C34 1,2 C34 1,3 C36 1,2 C36 1,3 Pheophytin a Chlorophyll a Pheophytin b Total xanthophyll Lutein Chlorophyll b |
59/30 | 4000–650 | ATR | PLS | Dependent test set | LOO? | 0.87 0.85 0.87 0.62 0.83 0.79 0.77 0.72 0.75 0.71 0.61 0.75 0.72 |
41.63 27.43 60.10 (mg/kg) 1.07 1.26 4.29 4.02 (mg/kg) 2.42 0.32 0.10 0.41 0.71 0.21 (mg/kg) |
Samples from two seasons; quite poor test set validation results for colour pigments; improved results from fusion of UV–Vis and IR spectra | [142] |
| Olive oil | Tyrosol Tyrosol secoiridoids Hydroxytyrosol Hydroxytyrosol secoiridoids Total phenolics |
75/18 | 4000–400 | ATR | PLS | None | LOO | 0.32 0.30 0.17 0.19 0.44 |
4.98 105.7 9.96 106.1 162.1 (mg/kg) |
[126] | |
| Olive oil | Total phenolics | 70/30 | 4000–600 | ATR | PLS | Dependent test set | n/s | 0.998 | 0.072 g/L | [143] | |
| Beverages | |||||||||||
| Cachaça | Total phenolics | 32/16 | 4000–650 | ATR (liquid sample) | PLS | Ranked subset of samples (60% cal; 20% val; 20% test set) | n/s | 0.820 | 248 mg/L Much poorer results than fluorescence spectroscopy |
For test set validation; R2p = 0.690 and RMSEP = 318 mg/L | [144] |
| Grape juice | Total phenolics Anthocyanins |
49/16 | 4000–400 | ATR | PLS | Dependent test set (randomly selected samples) | Optimising no. of latent variables | 0.90 0.81 (cal) |
21 4.22 mg/100 mL (test set) |
Performed better than NIR for phenolic content | [137] |
| Shiraz wine | Total anthocyanins Total phenolics |
70/30 | 1700–950 | ATR (liquid sample) | PLS | Dependent test set | LOO | 0.61 0.60 |
32 mg/L 5.7 au |
Wines from 24 different Australian locations | [145] |
| Wine (red) | Gallic acid Catechin B1 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 | 4000–600 | ATR (liquid sample) | PLS using PRESS | Dependent test set | Segment validation | 0.83 0.78 0.8 0.85 0.85 0.86 0.85 0.81 0.85 0.69 0.82 0.88 0.76 0.86 0.84 0.85 0.86 0.85 0.88 0.89 0.89 0.85 0.85 0.85 0.85 0.85 0.89 0.86 |
3.42 7.26 4.99 128 9.76 1.07 3.14 0.63 13 2.56 0.34 2.96 0.06 2.57 1.47 20.7 1.44 0.48 1.19 1.03 6.49 0.41 0.79 0.91 3.98 5.5 261 47.2 (mg/L) |
Wines comprised four cultivars from 13 vinifications over two seasons; slightly less accurate at phenolic content compared to FT-NIR | [92] |
| Wine (red) | Gallic acid Catechin B1 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 | 4000–600 | Transmission | PLS using PRESS | Dependent test set | Segment validation | 0.85 0.85 0.84 0.91 0.87 0.86 0.84 0.83 0.82 0.84 0.87 0.84 0.82 0.88 0.85 0.86 0.84 0.86 0.88 0.9 0.84 0.88 0.85 0.87 0.85 0.82 0.92 0.89 |
4.57 5.39 3.91 132 9.87 1.02 2.8 0.625 13 1.59 0.328 4.15 0.0645 4.1 2.1 24.2 1.28 0.513 1.24 1.12 8.85 0.463 0.831 1.01 4.7 7.49 224 56.5 (mg/L) |
Wines comprised four cultivars from 13 vinifications over two seasons; slightly less accurate at phenolic content compared to FT-NIR | [92] |
| Wine (red, rose and white) | Total phenolics Total anthocyanins |
35/- | 4000–650 | ATR | PLS | Cross-validation only | LOO | 0.91 0.86 |
269.2 mg/L 1.79 mg/L |
Seven wine samples (red, rose, white) each at five different time points | [146] |
| Wine (red and white) | Total polyphenols Malvidin-3-O-glucoside Peonidin-3-O-glucoside Petunidin-3-O-glucoside Delphinidin-3-O-glucoside Delphinidin-3-O-(6-acetyl)-glucoside Petunidin-3-O-(6-acetyl)-glucoside Peonidin-3-O-(6-acetyl)-glucoside Malvidin-3-O-(6-acetyl)-glucoside Delphinidin-3-O-(6-p-coumaroyl)-glucoside Malvidin-3-O-(6-p-coumaroyl)-glucoside o-coumaric acid |
51/21 | 4000–650 | ATR | PLS | Dependent test set | LOO | 0.75 0.53 0.56 0.67 0.71 0.27 0.29 0.31 0.41 0.45 0.69 0.63 |
249.1 6.87 0.38 1.1 0.73 0.15 0.24 0.22 2.59 0.12 0.65 0.33 (mg/L) |
Samples from various locations across two seasons | [147] |
| Other foods | |||||||||||
| Chocolate | (+)-Catechin (+)-Epicatechin Total phenolics TAC (DPPH) TAC (ORAC) |
18/7 | 4000–550 | ATR | PLS | Semi-independent (7 randomly selected commercial chocolate brands) R2p = 0.86, 0.72, 0.88, 0.89, 0.90; RMSEP = 0.10, 0.57, 5.08, 13.07, 37.92 mg/g |
Nine-fold cross-validation | 0.94 0.87 0.93 0.92 0.89 |
0.09 0.58 4.21 1.05 11.38 (mg/g) |
18 different types of chocolate containing 35–100% cacao | [31] |
| Honey | Catechin Syringic acid Vanillic acid Chlorogenic acid TAC (DPPH) |
64/36 | 3000–2800, 1800–700 | ATR | PLS | Dependent test set (ranked subset of samples) | LOO | 0.999 0.992 0.946 0.994 0.955 |
0.40 1.08 0.45 0.43 (µg/g) 1.63 (mg/100 g) |
Models based on Raman spectra were slightly better than FTIR | [148] |
Abbreviations: LOO = leave-one-out cross-validation; n/s = not specified; SFA = saturated fatty acids; MUFA = monounsaturated fatty acids; PUFA = polyunsaturated fatty acids; TAC = total antioxidant capacity.