Development of FTIR spectroscopy in combination with chemometrics for analysis of rat meat in beef sausage employing three lipid extraction systems

Figures & data

Table 1. Formula of the beef–rat meat sausage.

Ingredients	Rat meat concentration and weight of each ingredient (g)
	0%	10%	20%	30%	40%	50%	60%	70%	80%	90%	100%
Beef	250	225	200	175	150	125	100	75	50	25	-
Rat meat	-	25	50	75	100	125	150	175	200	225	250
Tapioca flour, egg, and spices	190	190	190	190	190	190	190	190	190	190	190

Figure 1. FTIR spectra of the lipid extracted from beef–rat meat sausage at concentration 0% (beef lipid) and 100% (rat lipid) using Bligh and Dyer method (a), Folch method (b), and Soxhlet method (c). Rat lipid (green), beef lipid (red).

Figure 2. The overlay of FTIR spectra of the lipid extracted from beef–rat meat sausage at concentration 100% (rat lipid) using Bligh and Dyer (blue), Folch (red), and Soxhlet (green) method, (a) 1745 cm⁻¹ (b) 1711 cm⁻¹ (c) 1232 cm⁻¹ (d) 1161 cm⁻¹ (e) 1095 cm^−1.

Figure 3. Score plot of PCA of the spectrum of the lipid extracted from beef–rat meat sausage (rat lipid 100% and beef lipid 100%) with Bligh and Dyer (a), Folch (b), and Soxhlet (c) using PC1 vs PC2. Rat lipid group (A), beef lipid group (B).

Figure 4. Score plot of PCA of lipid extracted from beef–rat meat sausage (rat lipid 100% and beef lipid 100%) and the market samples with Soxhlet method using PC1 vs PC2 (a), PC2 vs PC3 (b), and PC3 vs PC4 (c). Rat lipid group (A), beef lipid group (B), and market sample group (S).

Table 2. PLS regression analysis result of the spectra of rat lipid and beef lipid extracted using three different lipid extraction methods.

Lipid extraction methods	Calibration equation (calibration)	R^2 (calibration)	RMSEC	Calibration equation (calibration)	R^2 (validation)	RMSEP
Bligh and Dyer	y = 0.919 x + 4.360	0.945	2.73%	NA	NA	NA
Folch	y = 0.999 x – 0.265	0.991	1.73%	y = 0.698 x + 9.720	0.458	18.90%
Soxhlet	y = 1.002 x + 0.089	0.992	1.69%	y = 0.966 x + 1.250	0.983	4.21%

*NA: not available

Table 3. Relative percentage of fatty acid compositions of rat lipid and beef lipid extracted using three different extraction methods.

	Rat			Beef
Fatty acid	Bligh and Dyer	Folch	Soxhlet	Bligh and Dyer	Folch	Soxhlet	Significant value
C6:0	0.00	0.00	0.00	0.00	0.00	0.00	-
C8:0	0.02	0.02	0.03	0.01	0.01	0.01	0.057
C10:0	0.07	0.07	0.12	0.03	0.04	0.04	0.090
C11:0	0.01	0.01	0.01	0.00	0.00	0.00	-
C12:0	0.97	0.98	1.60	0.10	0.12	0.13	0.036*
C13:0	0.01	0.01	0.02	0.01	0.02	0.02	0.519
C14:0	2.26	2.43	2.89	2.28	2.76	2.47	0.925
C15:0	0.12	0.15	0.14	0.82	0.95	0.84	0.002*
C16:0	27.43	28.59	28.35	21.49	23.70	20.80	0.003*
C17:0	0.71	0.21	0.17	2.36	1.74	1.42	0.011*
C18:0	6.60	7.23	5.89	1.15	0.97	1.13	0.000*
C20:0	0.30	0.18	0.15	0.19	0.19	0.16	0.557
C21:0	0.00	0.01	0.00	0.02	0.02	0.01	0.047*
C22:0	0.00	0.07	0.07	0.03	0.03	0.00	0.353
C23:0	0.01	0.01	0.05	0.01	0.02	0.00	0.411
C24:0	0.05	0.07	0.12	0.03	0.02	0.23	0.861
Total of saturated fatty acid	38.56	40.04	39.60	28.54	30.59	27.24	0.001*
C14:1	0.17	0.17	0.23	0.47	0.56	0.59	0.001*
C15:1	0.00	0.00	0.00	0.03	0.00	0.00	0.423
C16:1	4.27	4.58	5.15	3.12	3.39	3.30	0.007*
C17:1	0.00	0.13	0.00	0.89	0.92	0.87	0.000*
C18 unsaturated	47.15	49.48	46.84	53.51	58.46	54.17	0.013*
C20 unsaturated	3.65	2.09	1.29	2.64	0.79	1.09	0.405
C22 unsaturated	1.06	0.37	0.23	0.33	0.04	0.04	0.203
C24:1	0.00	0.04	0.16	0.00	0.00	0.00	0.300
Total of unsaturated fatty acid	56.30	56.86	53.89	60.98	64.17	60.06	0.017*
Total of unknown compound	5.14	3.10	6.51	10.48	5.24	12.70	Not tested

*Significant at p = 0.95.

Figure 5. Chromatogram of 37 Component FAME Mix mixture standard. Peak elution order: 1.C6:0, 2.C8:0, 3.C10:0, 4.C11:0, 5.C12:0, 6.C13:0, 7.C14:1 cis 9, 8.C14:0, 9.C15:1 cis 9, 10.C15:0, 11.C16:1 cis 9, 12.C16:0, 13.C17:1 cis 10, 14.C17:0, 15–18.Unsaturated C18, 19.C18:0, 20–24.Unsaturated C20, 25.C20:0, 26.C21:0, 27–29.Unsaturated C22, 30.C22:0, 31.C23:0, 32.C24:1 cis 15, 33.C24:0.