Table 1.
Summary table of reported to date Raman studies on botanicals
| Target | Objective | Instrumentation/parameters | Peaks with increase in intensity | Peaks with decrease in intensity | Conclusion |
|---|---|---|---|---|---|
| Disease diagnostics | |||||
| Tomato, leaf | Liberibacter disease in tomatoes [8] | Handheld spectrometer (λ = 830 nm; P = 495 mW; T = 1 s) | – | 747 cm−1 (pectin); 1000, 1115, 1155, 1184, 1218 and 1525 cm−1 (carotenoids) | Liberibacter disease in tomatoes is associated with degradation and fragmentation of host carotenoids and pectin |
| Orange and grapefruit, leaves | Huanglongbing (HLB) or citrus greening [23] | Handheld spectrometer (λ = 830 nm; P = 495 mW; T = 1 s) | 1601–1630 cm−1 (phenylpropanoids; 1440–1455 cm−1 (aliphatic) | 1184 and 1218 cm−1 (xylan, carotenoids); 1525 cm−1 (carotenoids), as well as 1288 cm−1 (aliphatic); 1155 and 1326 cm−1 (cellulose) | HLB is associated with an increase in phenylpropanoids and decrease in xylan, carotenoids and cellulose |
| Orange and grapefruit, leaves | Nutrient deficiency in citrus trees [23] | Handheld spectrometer (λ = 830 nm; P = 495 mW; T = 1 s) | 1247, 1601–1630 cm−1 (phenylpropanoids; 1440–1455 cm−1 (aliphatic) | 1184 and 1218 cm−1 (xylan, carotenoids) | ND is associated with an increase in phenylpropanoids |
| Orange, leaf | Canker [22] | Handheld spectrometer (λ = 830 nm; P = 495 mW; T = 1 s) | – | 1601–1630 cm−1 (phenylpropanoids) | Canker is associated with a decrease in phenylpropanoids content |
| Orange, leaf | HLB and blight [22] | Handheld spectrometer (λ = 830 nm; P = 495 mW; T = 1 s) | – | – | Diagnostics was achieved via the use of PLS-DA |
| Wheat, grain | Ergot [15] | Handheld spectrometer (λ = 1064 nm; P = 200 mW; T = 30 s) | 1650 and 1667 cm−1 (proteins) | – | ergot infection may be associated with expression and deposition of alpha-helical and beta-sheet proteins |
| Wheat, grain | Black tip [15] | Handheld spectrometer (λ = 1064 nm; P = 200 mW; T = 30 s) | 1348 cm−1 (monomeric sugars) and 1600 cm−1 (lignin); shift of 862 peak to 856 cm−1 (pectin) | 862 and 937 cm−1 (starch) | black tip may degrade lignin and ferment starch into monomeric sugars; esterification of pectin |
| Sorghum, grain | Mold [15] | Handheld spectrometer (λ = 1064 nm; P = 200 mW; T = 30 s) | shift of 856 peak to 862 cm−1 (pectin); change in ratio between 1518 cm−1 and 1541 cm−1 peaks (carotenoids) | 1600 and 1630 cm−1 (phenylpropanoids) | Degradation of phenylpropanoids; a decrease in methylesterfication of pectin caused by the infections; suggest a decrease in the length of conjugated double bonds of carotenoids |
| Sorghum, grain | Ergot [15] | Handheld spectrometer (λ = 1064 nm; P = 200 mW; T = 30 s) | 1150, 940, 1124 and 1083 cm−1 (monomeric sugars); shift of 856 peak to 862 cm−1 (pectin); change in ratio between 1518 cm−1 and 1541 cm−1 peaks (carotenoids) | 1600 and 1630 cm−1 (phenylpropanoids) | ergot hydrolyzes starches to produce monomeric sugars; a decrease in methylesterfication of pectin caused by the infections; suggest a decrease in the length of conjugated double bonds of carotene |
| Maize, grain | Fusarium spp [16] | Handheld spectrometer (λ = 1064 nm; P = 200 mW; T = 30 s) | 1658 cm−1 (protein); 1153 cm−1 (starch) | 1600 and 1633 cm−1 (phenylpropanoids); 1547 cm−1 (shifted from 1523 cm−1 in healthy) species (carotenoids) | Fusarium infection is associated with degradation of phenylpropanoids and deposition of protein in maize kernels; pathogen converts monomeric sugars polymeric carbohydrates |
| Maize, grain | Aspergillus flavus [16] | Handheld spectrometer (λ = 1064 nm; P = 200 mW; T = 30 s) | 1003–1115 cm−1 (monomeric sugars); 1600–1633 (phenylpropanoids) | 1600 and 1633 cm−1 (phenylpropanoids); 1547 cm−1 (shifted from 1523 cm−1 in healthy) species (carotenoids); 1153 cm−1 (starch) | A. flavus is associated with a breakdown maize starch into monomeric sugars |
| Maize, grain | A. niger [16] | Handheld spectrometer (λ = 1064 nm; P = 200 mW; T = 30 s) | 1153 cm−1 (starch); 1600–1633 (phenylpropanoids) | 1600 and 1633 cm−1 (phenylpropanoids); 1547 cm−1 (shifted from 1523 cm−1 in healthy) species (carotenoids) | A. niger converts monomeric sugars polymeric carbohydrates |
| Maize, grain | Diplodia spp. [16] | Handheld spectrometer (λ = 1064 nm; P = 200 mW; T = 30 s) | 1003–1115 cm−1 (monomeric sugars) | 1153 cm−1 (starch) | Diplodia is associated with a breakdown maize starch into monomeric sugars |
| Abutilon hybridum, leaf | Abutilon mosaic virus [29] | Handheld spectrometer (λ = 1064 nm; P = 200 mW; T = 8 s) | 1605–1629 (phenylpropanoids); 1440–1460 cm−1 (aliphatic) | – | Abutilon mosaic virus is associated with an increase in phenylpropanoids in Abutilon hybridum |
| Tomatoes, leaf | Tomato yellow leaf curl Sardinia virus (TYCLSV) [45] | Benchtop spectrometer (λ = 780 nm; P = 2mW; T = 5–10 s) | 1608 cm−1 (phenolic); 1483 cm−1 (aliphatic) | 1526 cm−1 (carotenoids); 1420, 1483 cm−1 (aliphatic), 1500, 1608 cm−1 (phenolic); 1353 cm−1 (unidentified); | Small changes in plant biochemistry |
| Tomatoes, leaf | Tomato spotted wilt virus (TSWV) [45] | Benchtop spectrometer (λ = 780 nm; P = 2mW; T = 5–10 s) | 1608 cm−1 (phenolic); 1438 cm−1 (aliphatic); 1353 cm−1 (unidentified); | 1483 cm−1 (aliphatic) | Small changes in plant biochemistry |
| Wheat, leaf | Barley yellow dwarf virus (BYDV) [36] | Handheld spectrometer (λ = 830 nm; P = 495 mW; T = 1 s) | 1601–1630 cm−1 (phenylpropanoids) | 1000, 1115, 1156, 1186, 1218 and 1525 cm−1 (carotenoids) | BYDV is associated with an increase in phenylpropanoids and decrease in carotenoids |
| Wheat, leaf | Wheat streak mosaic virus (WSMV) [36] | Handheld spectrometer (λ = 830 nm; P = 495 mW; T = 1 s) | 1601–1630 cm−1 (phenylpropanoids) | 1000, 1115, 1156, 1186 and 1218 cm−1 (carotenoids) | WSMV is associated with an increase in phenylpropanoids and decrease in carotenoids |
| Potato, tubers | Zebra chip [112] | Handheld spectrometer (λ = 830 nm; P = 495 mW; T = 1 s) | – | 1153 (carbohydrates) | Zebra chip is associated with degradation of carbohydrates in tubers |
| Potato, tubers | Virus Y [112] | Handheld spectrometer (λ = 830 nm; P = 495 mW; T = 1 s) | 1153 cm−1 (carbohydrates) | Virus Y is associated with an increase in carbohydrates in tubers | |
| Abiotic stresses | |||||
| Coleus lime (Plectranthus scutellarioides), leaves | Saline, light, drought and cold [26] | Benchtop spectrometer (λ = 532 nm; P = 10 mW; T = 10 s) | 620 and 740 cm−1 (anthocyanins) | 1000 and 1170 cm−1 (carotenoids) | Saline, light, drought and cold stresses cause an increase in anthocyanins and a decrease in carotenoids |
| Arabidopsis thaliana, leaves | Nitrogen deficiency [10] | Postable spectrometer (λ = 830 nm; P = 100 mW; T = 10 s) | – | 1064 cm−1 (nitrate) | 1046 cm–1 peak intensity correlates with the nitrate content in Arabidopsis plants |
| Rice, leaves | Nitrogen deficiency [8] | Handheld spectrometer (λ = 830 nm; P = 495 mW; T = 1 s) | 1600–1630 cm−1 (phenylpropanoids) | 1115–1218 cm−1 (carotenoids) | Nitrogen deficiency is associated with a decrease in carotenoids and increase in phenylpropanoids |
| Rice, leaves | Phosphorus and potassium deficiencies [8] | Handheld spectrometer λ = 830 nm; P = 495 mW; T = 1 s) | Small changes in 1600–1630 cm−1 (phenylpropanoids) | Small changes in 1115–1218 cm−1 (carotenoids) | Phosphorus and potassium deficiencies are associated with a decrease in carotenoids and increase in phenylpropanoids |
| Identification of plant species and their varieties; nutritional analysis | |||||
| Poison ivy, leaves | Farber et al. [36] | Handheld spectrometer (λ = 830 nm; P = 495 mW; T = 1 s) | 1717 cm−1 (carboxyl or ester groups) | 1717 cm−1 band can be used to identify poison ivy | |
| Peanuts, leaves and seeds | Farber et al. [36] | Handheld spectrometer (λ = 830 nm; P = 495 mW; T = 1 s) |
Identification: all bands Nutritional analysis: 1005 cm−1 (proteins), 1301 cm−1 (carbohydrates), 1443 cm−1 (oils), 1606 cm−1 (fiber), 1656 cm−1 (unsaturated fatty acids), and 1748 cm−1 (esters) |
Identification of peanut varieties can be achieved though spectroscopic analysis of leaves and seeds with 80% and 95% accuracy, respectively. RS can be used to predict relative concentration of proteins, carbohydrates, oils, fiber, unsaturated fatty acids and esters in peanut seeds | |
| Potato, tubers | Morey et al. [34] | Handheld spectrometer (λ = 830 nm; P = 495 mW; T = 1 s) |
Identification: all bands Nutritional analysis: 1126 cm−1 (starch), 1527 cm−1 (carotenoids), 1600 cm−1 (phenylpropanoids), 1660 cm−1 (proteins) |
Identification of potato varieties can be achieved though spectroscopic analysis of tubers with 77.5% accuracy. RS can be used to predict relative concentration of proteins, carotenoids, starch and phenylpropanoids in potato tubers | |
| Corn, kernels | Krimmer et al. [21] | Handheld spectrometer (λ = 830 nm; P = 495 mW; T = 1 s) |
Identification: all bands Nutritional analysis: 479 cm−1 (starch), 1527 cm−1 (carotenoids), 1600/1632 cm−1 (phenylpropanoids), 1000/1660 cm−1 (proteins) |
Identification of corn varieties can be achieved though spectroscopic analysis of kernels with 95% accuracy. RS can be used to predict relative concentration of proteins, carotenoids, and starch in corn kernels | |
| Citrus, fruits | Feng et al. [74] | Benchtop spectrometer (λ = 514 nm; P = 20 mW; T = 10 s) | All bands | RS can be used to identify citrus fruits | |
| Loquat, fruits | Zhu et al. [47] | Benchtop spectrometer (λ = 532 nm; P = 25 mW; T = 1 s) | 1602 cm−1 (lignin) | RS can be used to determine fruit ripening | |
| Tomatoes, fruits | Martin et al. [77] | Benchtop spectrometer (λ = 532 nm; P = 46–50 mW; T = 10 s) | 1150, 1257 cm−1 (carotenoids) | RS can be used to predict tomato ripeness | |
| Mandarin oranges, fruits | Nekvapil et al. [79] | Benchtop spectrometer (λ = 532 nm; P = 200 mW; T = 10 s) | 1100–1250, 1527 cm−1 (carotenoids) | RS can be used to predict fruit freshness | |
| Wheat, grain | Piot et al. [80] | Benchtop spectrometer (λ = ’red light’; P = 8 mW) | 471–485 cm−1 (starch), 1065–1140 cm−1 (lipids), 1630–1670 cm−1 (protein) | RS can be used to probe concentration of starch, lipids and proteins in the grain | |
| Coffee, beans | Keidel et al. [81] | Benchtop spectrometer (λ = 1064 nm; P = 300 mW) |
Identification: all bands Kahweol concentration: 1479 and 1567 cm−1 |
RS can be used to predict the geographical origins of coffee beans | |
| Hemp and cannabis | Sanchez et al. [8] | Handheld spectrometer (λ = 830 nm; P = 495 mW; T = 1 s) |
Identification: all bands Cannabinoid content: 780, 1295, 1623, and 1666 cm−1 |
RS can be used to identify cannabis varieties and determine concentrations of cannabinoids in the plant | |