Pre-treatment	Optimization parameters		Training set accuracy	Test set accuracy
Pre-treatment	c	g	Training set accuracy	Test set accuracy
Original spectra	default	default	86.88% (53/61)	70.00% (14/20)
MSC	default	default	88.52% (54/61)	75.00% (15/20)
SNV	default	default	90.16% (55/61)	75.00% (15/20)
First derivative	default	default	93.44% (57/61)	85.00% (17/20)
Second derivative	default	default	91.80% (56/61)	80.00% (16/20)