Anthocyanins are widely used in the food industry as an additive, improving antioxidant
capacity and strengthening the human immune system. However, rapid and
nondestructive detection methods are lacking. This study aimed to
develop a rapid and nondestructive method to detect anthocyanin
content in fresh purple maize leaves using hyperspectral reflectance.
Sensitivity bands were screened by analyzing the correlation between
the spectrum and anthocyanin, chlorophyll, and moisture content in
maize leaves with models constructed. Through a combination of the
sensitivity bands of the three components, the interference of
chlorophyll and moisture on the spectral detection of anthocyanin in
fresh leaves was analyzed. The results showed that the anthocyanin
sensitivity band was approximately 550 nm. The determination
coefficient and root mean square error of the optimal hyperspectral
model were 0.766 and 4.215 mg/g, respectively. After excluding
chlorophyll and moisture interference, the anthocyanin content
detection accuracy was improved by only 2% compared to that of the
original. These results indicate that hyperspectral technology can be
used to nondestructively detect anthocyanin content in fresh purple
maize leaves with good accuracy. Chlorophyll and moisture in the
leaves did not significantly influence anthocyanin content.
Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request.
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Hyperspectral Function Expression of Anthocyanin Content with the Sensitivity Band as the Independent Variable
Function
Expression
Linear
Quadratic
Power
Exponential
Logarithmic
Table 2.
Statistical Parameters of Foliar Main Components in Fresh Leaves (mg/g)
Foliar
Standard
Components
Minimum
Maximum
Mean
Median
Deviation
Anthocyanin
3.62
55.86
27.61
25.74
10.35
Chlorophyll
2.93
5.21
4.03
3.99
0.53
Moisture
637.79
773.45
725.99
726.71
26.29
Table 3.
Sensitivity Bands and Correlation Coefficients of Three Components Based on Different Transformations of Spectral Reflectance (P)
Anthocyanin
Chlorophyll
Moisture
Transformation
Sensitivity Band (nm)
Correlation Coefficient
Sensitivity Band (nm)
Correlation Coefficient
Sensitivity Band (nm)
Correlation Coefficient
P
548
−0.56
549
−0.52
975
−0.49
1/P
544
0.60
552
0.55
978
0.52
lg P
551
−0.62
563
−0.50
975
−0.48
1/lg P
546
0.58
549
0.53
978
0.54
550
0.68
746
0.63
947
−0.64
550
−0.81
748
−0.70
947
0.72
552
0.77
750
0.64
947
−0.69
558
−0.75
741
−0.68
949
0.66
Table 4.
Hyperspectral Models of Foliar Anthocyanin Content in Their Sensitive Bands Based on Different Transformations of Spectral Reflectance (P)a
Transformation
Sensitivity Band (nm)
Hyperspectral Model
(training sets)
(validating sets)
P
548
0.311
0.306
0.430
0.423
0.329
0.308
0.403
0.389
0.426
0.410
1/P
544
0.354
0.344
0.452
0.413
0.387
0.358
0.461
0.453
0.448
0.430
lg P
551
0.352
0.344
0.418
0.395
0.340
0.310
0.426
0.412
1/lg P
546
0.329
0.322
0.405
0.411
0.340
0.319
0.453
0.446
P′
550
0.511
0.497
0.697
0.652
0.361
0.339
0.685
0.681
0.596
0.602
550
0.593
0.567
0.716
0.719
0.498
0.562
0.772
0.766
0.568
0.518
552
0.575
0.553
0.718
0.709
0.316
0.277
0.711
0.715
0.616
0.610
558
0.501
0.488
0.718
0.713
0.510
0.481
0.717
0.698
0.678
0.640
${{\rm{W}}_{548}}$ represents reflectance at 548 nm.
Table 5.
Hyperspectral Model of Foliar Anthocyanin Content Excluding the Interference of Chlorophyll Based on Different Transformations of Spectral Reflectance (P)a
Transformation
Integration
Hyperspectral Model
(training sets)
(validating sets)
P
0.424
0.381
1/P
0.443
0.426
lg P
0.421
0.397
1/lg P
0.447
0.415
P′
0.709
0.691
0.788
0.780
0.722
0.696
0.719
0.711
${P_{\rm{ant}}} + {P_{\rm{chl}}}$, ${P_{\rm{ant}}} - {P_{\rm{chl}}}$, ${P_{\rm{ant}}} \times {P_{\rm{chl}}}$, and ${P_{\rm{ant}}}/{P_{\rm{chl}}}$ represent the addition, subtraction, multiplication, and division integration of anthocyanin and chlorophyll sensitivity bands, respectively. ${{\rm{W}}_{548 \cdot 549}}$ represents the integrated reflectance of anthocyanins at 548 nm and chlorophyll at 549 nm.
Table 6.
Hyperspectral Model of Foliar Anthocyanin Content Excluding the Interference of Moisture Based on Different Transformations of Spectral Reflectance (P)a
Transformation
Integration
Hyperspectral Model
(training sets)
(validating sets)
P
0.427
0.406
1/P
0.459
0.425
lg P
0.431
0.425
1/lg P
0.450
0.420
0.698
0.656
0.778
0.765
0.724
0.701
0.721
0.717
${P_{\rm{ant}}} + {P_{\rm{moi}}}$, ${P_{\rm{ant}}} - {P_{\rm{moi}}}$, ${P_{\rm{ant}}} \times {P_{\rm{moi}}}$, and ${P_{\rm{ant}}}/{P_{\rm{moi}}}$ represent the addition, subtraction, multiplication, and division integrations of anthocyanin and moisture-sensitivity bands, respectively. ${{\rm{W}}_{548 \cdot 975}}$ represents the integrated reflectance of anthocyanins at 548 nm and moisture at 975 nm.
Tables (6)
Table 1.
Hyperspectral Function Expression of Anthocyanin Content with the Sensitivity Band as the Independent Variable
Function
Expression
Linear
Quadratic
Power
Exponential
Logarithmic
Table 2.
Statistical Parameters of Foliar Main Components in Fresh Leaves (mg/g)
Foliar
Standard
Components
Minimum
Maximum
Mean
Median
Deviation
Anthocyanin
3.62
55.86
27.61
25.74
10.35
Chlorophyll
2.93
5.21
4.03
3.99
0.53
Moisture
637.79
773.45
725.99
726.71
26.29
Table 3.
Sensitivity Bands and Correlation Coefficients of Three Components Based on Different Transformations of Spectral Reflectance (P)
Anthocyanin
Chlorophyll
Moisture
Transformation
Sensitivity Band (nm)
Correlation Coefficient
Sensitivity Band (nm)
Correlation Coefficient
Sensitivity Band (nm)
Correlation Coefficient
P
548
−0.56
549
−0.52
975
−0.49
1/P
544
0.60
552
0.55
978
0.52
lg P
551
−0.62
563
−0.50
975
−0.48
1/lg P
546
0.58
549
0.53
978
0.54
550
0.68
746
0.63
947
−0.64
550
−0.81
748
−0.70
947
0.72
552
0.77
750
0.64
947
−0.69
558
−0.75
741
−0.68
949
0.66
Table 4.
Hyperspectral Models of Foliar Anthocyanin Content in Their Sensitive Bands Based on Different Transformations of Spectral Reflectance (P)a
Transformation
Sensitivity Band (nm)
Hyperspectral Model
(training sets)
(validating sets)
P
548
0.311
0.306
0.430
0.423
0.329
0.308
0.403
0.389
0.426
0.410
1/P
544
0.354
0.344
0.452
0.413
0.387
0.358
0.461
0.453
0.448
0.430
lg P
551
0.352
0.344
0.418
0.395
0.340
0.310
0.426
0.412
1/lg P
546
0.329
0.322
0.405
0.411
0.340
0.319
0.453
0.446
P′
550
0.511
0.497
0.697
0.652
0.361
0.339
0.685
0.681
0.596
0.602
550
0.593
0.567
0.716
0.719
0.498
0.562
0.772
0.766
0.568
0.518
552
0.575
0.553
0.718
0.709
0.316
0.277
0.711
0.715
0.616
0.610
558
0.501
0.488
0.718
0.713
0.510
0.481
0.717
0.698
0.678
0.640
${{\rm{W}}_{548}}$ represents reflectance at 548 nm.
Table 5.
Hyperspectral Model of Foliar Anthocyanin Content Excluding the Interference of Chlorophyll Based on Different Transformations of Spectral Reflectance (P)a
Transformation
Integration
Hyperspectral Model
(training sets)
(validating sets)
P
0.424
0.381
1/P
0.443
0.426
lg P
0.421
0.397
1/lg P
0.447
0.415
P′
0.709
0.691
0.788
0.780
0.722
0.696
0.719
0.711
${P_{\rm{ant}}} + {P_{\rm{chl}}}$, ${P_{\rm{ant}}} - {P_{\rm{chl}}}$, ${P_{\rm{ant}}} \times {P_{\rm{chl}}}$, and ${P_{\rm{ant}}}/{P_{\rm{chl}}}$ represent the addition, subtraction, multiplication, and division integration of anthocyanin and chlorophyll sensitivity bands, respectively. ${{\rm{W}}_{548 \cdot 549}}$ represents the integrated reflectance of anthocyanins at 548 nm and chlorophyll at 549 nm.
Table 6.
Hyperspectral Model of Foliar Anthocyanin Content Excluding the Interference of Moisture Based on Different Transformations of Spectral Reflectance (P)a
Transformation
Integration
Hyperspectral Model
(training sets)
(validating sets)
P
0.427
0.406
1/P
0.459
0.425
lg P
0.431
0.425
1/lg P
0.450
0.420
0.698
0.656
0.778
0.765
0.724
0.701
0.721
0.717
${P_{\rm{ant}}} + {P_{\rm{moi}}}$, ${P_{\rm{ant}}} - {P_{\rm{moi}}}$, ${P_{\rm{ant}}} \times {P_{\rm{moi}}}$, and ${P_{\rm{ant}}}/{P_{\rm{moi}}}$ represent the addition, subtraction, multiplication, and division integrations of anthocyanin and moisture-sensitivity bands, respectively. ${{\rm{W}}_{548 \cdot 975}}$ represents the integrated reflectance of anthocyanins at 548 nm and moisture at 975 nm.