Portable optical spectroscopy and machine learning techniques for quantification of the biochemical content of raw food materials

Table 2 PLSR accuracy on pomegranate TSS, TA, pH, vitamin C and gallic acid by means of the best combinations of pre-processing techniques in the season 2021 and 2020–2021 (TSS only)

Parameter	DEV. ST	Pre-processing combination	RMSE	R²	RPD	LVs
Calibration
TSS 2021	3.06	Raw spectra	1.05	0.88	2.93	8
TSS 2021	3.06	2nd Der, SNV	1.07	0.88	2.87	5
TA	7.23	Log, 2nd Der, SNV	4.25	0.65	1.70	3
TA	7.23	1st Der, SNV	4.23	0.66	1.71	4
pH	0.24	1st Der, SNV	0.10	0.83	2.41	5
pH	0.24	2nd Der, SNV	0.10	0.84	2.49	5
Vitamin C	1.59	Raw spectra	1.33	0.30	1.20	7
Vitamin C	1.59	1st Der, SNV	1.29	0.34	1.23	4
Gallic acid	1.43	Log, 2nd Der, SNV	1.34	0.12	1.07	1
Gallic acid	1.43	2nd Der, SNV	1.34	0.12	1.07	1
TSS 20–21	2.94	Log, 2nd Der, SNV	1.07	0.87	2.75	6
TSS 20–21	2.94	2nd Der, SNV	1.08	0.87	2.73	6
Validation
TSS 2021	2.93	Raw spectra	1.04	0.87	2.82	8
		2nd Der, SNV	1.28	0.80	2.29	5
TA	7.04	1st Der, SNV	5.43	0.40	1.30	3
		Log, 2nd Der, SNV	5.19	0.46	1.36	4
pH	0.21	2nd Der, SNV	0.15	0.49	1.40	5
		1st Der, SNV	0.15	0.47	1.40	5
Vitamin C	3.15	1st Der, SNV	2.19	0.36	1.44	7
		Raw spectra	2.27	0.32	1.39	4
Gallic acid	3.04	Log, 2nd Der, SNV	3.04	0.06	1.00	1
		2nd Der, SNV	3.04	0.06	1.00	1
TSS 20–21	2.78	Log, 2nd Der, SNV	1.29	0.78	2.16	6
		2nd Der, SNV	1.25	0.80	2.23	6

ISSN: 2662-4044