Near-Infrared Spectroscopy for Classification of Oranges and Prediction of the Sugar Content

Figures & data

Figure 1 Experimental setup for the spectral measurement of orange juice.

Figure 2 The original absorbance spectral curves of all samples.

Figure 3 The spectral curves after Savitzky-Golay smoothing and MSC of all samples.

Figure 4 Principal component scores image (PC1 × PC2) of four varieties of oranges.

Table 1 Prediction results for unknown samples by BP neural network model

Sample number	Predicted value	Standard value	Sample number	Predicted value	Standard value
(1)	1.00589	1	(31)	3.05929	3
(2)	1.03106	1	(32)	3.08202	3
(3)	1.01913	1	(33)	3.01581	3
(4)	1.00242	1	(34)	2.91456	3
(5)	1.00242	1	(35)	2.9687	3
(6)	1.00042	1	(36)	2.92575	3
(7)	1.02041	1	(37)	2.96902	3
(8)	1.00082	1	(38)	2.95132	3
(9)	1.02066	1	(39)	3.16438	3
(10)	1.08772	1	(40)	3.14563	3
(11)	1.04352	1	(41)	3.00095	3
(12)	1.0005	1	(42)	2.93608	3
(13)	1.00021	1	(43)	3.03401	3
(14)	1.00449	1	(44)	3.00027	3
(15)	1.00868	1	(45)	3.14278	3
(16)	2.0837	2	(46)	3.99963	4
(17)	2.08919	2	(47)	3.99909	4
(18)	2.07986	2	(48)	3.99932	4
(19)	2.0249	2	(49)	3.99894	4
(20)	2.04841	2	(50)	3.9993	4
(21)	2.04591	2	(51)	3.99941	4
(22)	2.0193	2	(52)	3.9987	4
(23)	2.08439	2	(53)	3.98585	4
(24)	1.99692	2	(54)	3.99961	4
(25)	2.0051	2	(55)	3.99965	4
(26)	2.02734	2	(56)	3.9988	4
(27)	2.09824	2	(57)	3.99905	4
(28)	2.01314	2	(58)	3.9986	4
(29)	2.14021	2	(59)	3.99912	4
(30)	2.13687	2	(60)	3.99523	4

Figure 5 First five principal components calculated from the Shatangju spectral curve in the training set of PCA model.

Figure 6 First five principal components calculated from the Huangyanbendizao orange spectral curve in the training set of PCA model.

Figure 7 Loadings of first five principal components from the Shatangju across the entire spectral region.

Figure 8 Loadings of first five principal components from the Huangyanbendizao across the entire spectral region.

Figure 9 Vis/NIR calibration results of sugar content for 55 Shatangju samples from the PLS model.

Figure 10 Vis/NIR prediction results of sugar content for 20 Shatangju samples from the PLS model.

Figure 11 Vis/NIR calibration results of sugar content for 55 Huangyanbendizao samples from the PLS model.

Figure 12 Vis/NIR prediction results of sugar content for 20 Huangyanbendizao samples from the PLS model.