Quantitative Identification of Adulterated Sichuan Pepper Powder by Near-Infrared Spectroscopy Coupled with Chemometrics

Table 2

Results of PLS calibration models with different mathematical pretreatments on spectra.

Components	Mathematical pretreatment	Number of principal components	PLS
			Calibration set; ()		Prediction set; ()
				SEC/%		SEP/%	RPD
Sichuan pepper powder	No processing	10	0.961	3.29	0.929	4.38	3.75
	SNV	10	0.984	2.10	0.970	2.87	5.73
	MSC	10	0.984	2.12	0.971	2.81	5.84
	Maximum/minimum normalized	10	0.974	2.67	0.962	3.21	5.12
	First derivative + SNV	9	0.969	2.90	0.967	2.99	5.51
	Second derivative + MSC	9	0.969	2.92	0.936	4.15	3.98
Wheat bran	No processing	10	0.965	2.64	0.846	5.29	2.55
	SNV	10	0.977	2.11	0.912	3.99	3.38
	MSC	9	0.977	2.13	0.909	4.24	3.18
	Maximum/minimum normalized	10	0.973	2.32	0.899	4.27	3.16
	First derivative + SNV	10	0.974	2.27	0.969	2.38	5.66
	Second derivative + MSC	10	0.959	2.84	0.900	4.26	3.16
Rice bran	No processing	10	0.897	4.44	0.860	5.21	2.68
	SNV	10	0.945	3.25	0.937	3.49	4.00
	MSC	10	0.944	3.29	0.948	3.19	4.38
	Maximum/minimum normalized	10	0.928	3.71	0.940	3.41	4.09
	First derivative + SNV	10	0.928	3.71	0.940	3.41	4.09
	Second derivative + MSC	9	0.897	4.44	0.797	6.27	2.23
Corn flour	No processing	10	0.979	2.05	0.916	3.89	3.46
	SNV	10	0.986	1.66	0.944	3.18	4.23
	MSC	9	0.987	1.59	0.946	3.13	4.29
	Maximum/minimum normalized	9	0.984	1.75	0.930	3.54	3.80
	First derivative + SNV	10	0.982	1.89	0.967	2.46	5.47
	Second derivative + MSC	10	0.969	2.46	0.922	3.76	3.58
Rosin powder	No processing	10	0.984	1.75	0.989	1.45	9.69
	SNV	10	0.996	0.83	0.994	1.10	12.8
	MSC	10	0.996	0.87	0.995	1.03	13.7
	Maximum/minimum normalized	9	0.991	1.28	0.989	1.50	9.38
	First derivative + SNV	7	0.993	1.13	0.992	1.24	11.4
	Second derivative + MSC	6	0.993	1.20	0.989	1.49	9.41