Prediction of Polyphenol Fraction in Virgin Olive Oil Using Mid-Infrared Attenuated Total Reflectance Attenuated Total Reflectance Accessory–Mid-Infrared Coupled With Partial Least Squares Regression

Figures & data

Figure 1 The absorbance spectra of a virgin olive oil in the MIR spectral region (4000–600 cm^–1).

Figure 2 Principal component analysis (PCA) performed on the (first derivative pre-treated) absorbance spectra of all olive oil samples (n = 100). The red filled circles are the two spectral outliers in the olive oil samples. PC-1: principal component-1; PC-2: principal component-2.

Figure. 3 Plot of the predicted and measured values for total phenolic content, obtained from the final PLS model developed from the MIR spectra.

Table 1 Explained variances (%) of PCs used in the PLS model

Explained	Factor	Factor	Factor	Factor	Factor	Factor	Factor
	1	2	3	4	5	6	7
Calibration	40,61	83,14	94,2	97,88	98,71	99,03	99,24
Validation	33,55	70,7	90,05	96,1	97,52	98,07	98,44

Table 2 Prediction of total phenolic content of external validation

Samples	y-Predicted	y-Deviation	y-Reference
71	6,4474	0,3389	6,4560
72	7,0879	0,2791	7,1200
73	3,9566	0,3009	3,9850
74	8,2307	0,1859	8,4500
75	6,8376	0,2272	6,8460
76	4,5312	0,3167	4,5300
77	6,8230	0,1460	6,7700
78	6,3490	0,2996	6,2800
79	7,9074	0,2832	7,9300
80	7,5223	0,2649	7,5000
81	6,0080	0,2833	5,9800
82	5,4139	0,2786	5,4000
83	6,2790	0,3173	6,2500
84	4,5533	0,2986	4,5800
85	6,3593	0,4967	6,3760
86	1,1440	0,4473	1,1700
87	7,6532	0,4394	7,6700
88	1,2334	0,5244	1,2950
89	6,2466	0,5178	6,2400
90	7,1615	0,5004	7,1700
91	5,2579	0,5173	5,4580
92	7,0076	0,6189	7,1100
93	6,3081	0,6519	6,3200
94	7,5277	0,7387	7,5300
95	6,9973	0,3014	6,9700
96	9,6707	0,1593	9,6500
97	8,2466	0,1827	8,3890
98	2,8696	0,2059	2,8670
99	1,1902	0,2541	1,3200
100	6,3279	0,5663	6,3300

Table 3 Statistical parameters carried out by external validation on PLS

External validation	LVs	Rp^2	RMSEP	Bias	RPD	REP%
	7	0.998	0.0719	–0.0264	13.88	1.1375