Geographical origin traceability of foxtail millet based on the combination of multi-element and chemical composition analysis

Figures & data

Table 1. Information on the foxtail millet varieties employed in this study, and weather conditions in the growing seasons in different regions.

Region	Varieties	Latitude(°)	Longitude(°)	Accumulative temperature (°C)	Sunshine duration (h)	Precipitation (mm)
Hebei province (HB)	Jigu 19, Heng 2015–3, 14–628, RS358, 14–697, Heng 2015–2, G239	38N	114E	3 032	572.3	169.4
Henan province (HN)	Jigu 19, Heng 2015–3, 14–628, RS358, 14–697, Heng 2015–2, G239	34N	113E	3 091	641.9	117.7
Shandong province (SN)	Jigu 19, Heng 2015–3, 14–628, RS358, 14–697, Heng 2015–2, G239	36N	117E	3 144	802.7	245.3

Table 2. Mineral content in foxtail millets from different regions.

Mineral element	Hebei	Henan	Shandong	Mean	SEM	P-value
Ca (mg/kg)	100.22^a	108.87^a	112.23^a	107.11	6.20	0.307
K (g/kg)	1.91^b	2.13^a	2.18^a	2.07	0.14	0.010
Mg (mg/kg)	866.01^b	885.45^a	887.17^a	879.54	11.75	0.009
P (g/kg)	2.73^b	3.10^a	3.12^a	2.98	0.22	0.003
Fe (mg/kg)	20.39^a	27.61^a	20.55^a	22.85	4.12	0.111
Mn (mg/kg)	12.42^a	13.28^a	12.23^a	12.64	0.56	0.195
Cu (mg/kg)	5.85^ab	6.14^a	5.41^b	5.80	0.37	0.109
Zn (mg/kg)	26.08^b	30.33^a	29.89^a	28.77	2.34	0.017
Se (μg/kg)	36.55^b	36.85^a	38.99^a	37.46	1.33	0.033
Mo (μg/kg)	291.29^b	363.90^a	334.49^ab	329.89	36.52	0.018
Co (μg/kg)	23.20^a	9.10^b	7.83^b	13.38	8.53	0.000
Ni (μg/kg)	714.32^a	484.80^b	480.91^b	560.01	133.65	0.000
Rb (mg/kg)	4.14^b	12.02^a	10.60^a	8.92	4.20	0.000
Sr (mg/kg)	0.82^b	1.64^a	1.58^a	1.35	0.46	0.000
Cs (μg/kg)	14.18^b	55.80^a	47.79^a	39.26	22.08	0.000
Ba (μg/kg)	424.66^a	321.21^b	303.54^b	349.80	65.43	0.002

Note: Means in the same row with different superscripts indicate a significant difference (P < 0.05).

Table 3. Chemical composition of foxtail millets from different regions.

Components	Hebei	Henan	Shandong	Mean	SEM	P-value
Protein content (g/100g)	10.87^a	9.88^b	10.08^b	10.28	0.52	0.006
Fat content (g/100g)	2.70^b	3.99^a	3.52^c	3.40	0.65	0.000
Dietary fiber content (g/100g)	1.68^c	2.59^b	2.83^a	2.37	0.61	0.000
Amylose content (g/100g)	20.35^b	21.61^a	22.46^a	21.47	1.06	0.003
Ash content (g/100g)	1.31^b	1.45^a	1.41^a	1.39	0.07	0.004

Note: Means in the same row with different superscripts indicate a significant difference (P < 0.05).

Figure 1. Principal component analysis of millets from different regions. (a) PCA of mineral elements; (b) PCA of the combination of mineral elements and chemical compositions.

Table 4. Classification of foxtail millet samples in different regions and the percentage of observations that were correctly classified.

			Predicted group membership^a
			HB	HN	SD	Total
Original	Count	HB	7			7
		HN		7		7
		SD		1	6	7
	%		100	100	85.7	95.2^b
Cross-validated	Count	HB	7			7
		HN		7		7
		SD		1	6	7
	%		100	100	85.7	95.2^c

Note: ^aThe numbers of correctly classified observations are tabulated diagonally; ^b 95.2% of empirically grouped observations were correctly classified; ^c 95.2% of cross-validated grouped observations were correctly classified.

Figure 2. Score plot of discriminant functions 1 and 2 to discriminate millet from different regions.