Discriminant Analysis of Multiple Physicochemical Properties for Thai Rough Rice Varietal Authentication

Figures & data

Table 1  Rough rice samples collected from different areas in Thailand

Variety	Number of samples	Number of locations	Number of provinces
KDML105	66	66	16 ^a
PTT1	50	50	9 ^b
SPR60	39	39	10 ^c
CNT1	51	51	10 ^d
PSL2	53	53	7 ^e
^aKDML105 grains originated from Nakhon Ratchasima, Korn Kaen, Burirum, Mahasarakham, Roi Et, Si Sa Ket, Ubonratchathani, Udon Thani, Surin, Mukdahan, Yasothon, Kamphaeng Phet, Phayao, Lamphun, Chiang Rai, and Chiang Mai.
^bPTT1 grains originated from Pathum Thani, Nakhon Sawan, Nakhon Pathom, Phetchaburi, Ratchaburi, Phra Nakhon Si Ayutthaya, Chai Nat, Suphan Buri, and Kanchanaburi.
^cSPR60 grains originated from Nakhon Pathom, Ratchaburi, Phetchaburi, Phra Nakhon Si Ayutthaya, Suphan Buri, Chai Nat, Kanchanaburi, Sing Buri, Saraburi, and Nakhon Sawan.
^dCNT1 grains originated from Nakhon Pathom, Ratchaburi, Phra Nakhon Si Ayutthaya, Suphan Buri, Chai Nat, Uthaithani, Ang Thong, Kanchanaburi, Nakhon Sawan, and Nakhon Ratchasima.
^ePSL2 grains originated from Nakhon Pathom, Phitsanulok, Ratchaburi, Phra Nakhon Si Ayutthaya, Suphan Buri, Chai Nat, and Kanchanaburi.

Table 2  Pearson correlation coefficients for association of physicochemical properties of Thai rough rice samples

	A	B	C	D	E	F	G	H	I	J	K	L
A	1
B	0.042	1
C	0.059	0.072	1
D	−0.004	0.729**	−0.628**	1
E	−0.075	0.296**	−0.164**	0.346**	1
F	−0.174**	−0.356**	0.304**	−0.485**	0.513**	1
G	0.106	0.658**	−0.479**	0.844**	0.482**	−0.504**	1
H	−0.747**	−0.001	−0.013	0.006	0.056	0.106	−0.053	1
I	0.207**	−0.065	0.207**	−0.191**	−0.174**	−0.106	−0.065	−0.219	1
J	−0.400**	−0.060	0.088	−0.108	−0.074	0.080	−0.158*	0.211	0.692**	1
K	−0.023	0.072	−0.009	0.066	0.472**	0.151*	0.313**	−0.039	−0.228**	−0.213**	1
L	−0.221**	−0.195**	0.062	−0.200**	−0.271**	−0.105	−0.160**	0.368**	0.346**	0.290**	−0.524**	1
A: hundred-rough rice grain weight (g dry basis); B: rough rice length (mm); C: rough rice width (mm); D: rough rice length to width ratio; E: brown rice length (mm); F: brown rice width (mm); G: brown rice length to width ratio; H: rough rice moisture content (g/100 g); I: brown rice crude protein content (g/100 g dry solids); J: milled rice crude protein content (g/100 g dry solids); K: apparent amylose content (g/100 g dry solids); L: alkali spreading value.
*Significant at P ≤ 0.05 (2-tailed); **P ≤ 0.01 (2-tailed).

Table 3  Physicochemical properties of five Thai rough rice varieties

	Mean and standard deviation
Properties	KDML105	PTT1	SPR60	CNT1	PSL2
Hundred grains weight (g dry basis)	2.50 ± 0.02^a	2.36 ± 0.04^d	2.31 ± 0.07^e	2.48 ± 0.04^b	2.43 ± 0.02^c
Rough rice length (mm)	10.64 ± 0.38^bc	10.79 ± 0.49^ab	10.60 ± 0.36^bc	10.90 ± 0.50^a	10.68 ± 0.41^ac
Rough rice width (mm)	2.67 ± 0.09^a	2.69 ± 0.06^a	2.63 ± 0.08^b	2.67 ± 0.11^a	2.70 ± 0.10^a
Rough rice length to width ratio	3.99 ± 0.20^ad	4.02 ± 0.21^ac	4.04 ± 0.17^ab	4.10 ± 0.26^a	3.96 ± 0.20^bcd
Brown rice length (mm)	7.67 ± 0.24^b	7.72 ± 0.29^b	7.98 ± 0.27^a	8.01 ± 0.23^a	7.99 ± 0.30^a
Brown rice width (mm)	2.18 ± 0.10^c	2.21 ± 0.09^b	2.26 ± 0.08^a	2.23 ± 0.07^ab	2.21 ± 0.08^b
Brown rice length to width ratio	3.53 ± 0.13^b	3.49 ± 0.14^b	3.54 ± 0.13^b	3.60 ± 0.11^a	3.61 ± 0.14^a
Initial moisture content (g/100 g)	16.16 ± 1.72^c	19.85 ± 2.41^a	21.18 ± 3.08^a	15.72 ± 0.82^c	18.35 ± 1.93^b
Brown rice protein content (g/100 g dry solids)	9.23 ± 0.23^b	9.60 ± 0.58^a	8.03 ± 0.51^d	8.52 ± 0.24^c	9.81 ± 0.24^a
Milled rice protein content (g/100 g dry solids)	6.98 ± 0.20^d	8.14 ± 0.49^a	7.29 ± 0.47^c	6.81 ± 0.18^e	7.60 ± 0.35^b
Apparent amylose content (g/100 g dry solids)	15.58 ± 1.12^d	16.30 ± 1.07^c	24.07 ± 1.93^b	28.43 ± 1.14^a	28.58 ± 1.18^a
Alkali spreading value	6.96 ± 0.08^a	6.91 ± 0.14^ab	6.62 ± 0.53^c	5.21 ± 0.20^d	6.87 ± 0.11^b
In a row, means and standard deviation tagged with the same alphabet are not significant difference (P < 0.05).

Table 4  Discriminant coefficients of variety group based on individual physicochemical attribute

	Identification function coefficients*
Attribute	KDML105	PTT1	SPR60	CNT1	PSL2
Hundred-grain weight (g dry basis)	1250.309	1181.725	1149.807	1241.338	1213.609
	(-1563.783)	(-1397.101)	(-1322.737)	(-1541.446)	(-1473.419)
Brown rice length (mm)	125.303	127.544	132.269	132.472	131.730
	(-480.818)	(-498.114)	(-535.579)	(-537.220)	(-531.238)
Brown rice width (mm)	337.495	348.501	352.823	348.251	345.702
	(-366.360)	(-390.536)	(-400.356)	(-389.979)	(-384.314)
Brown rice length to width ratio	216.514	213.389	218.425	221.750	222.006
	(-385.134)	(-374.144)	(-391.935)	(-403.908)	(-404.838)
Rough rice moisture content (g/100 g)	3.252	4.017	4.339	3.187	3.773
	(-27.409)	(-40.992)	(-47.548)	(-26.395)	(-36.3538)
Brown rice crude protein (g/100 g dry solids)	67.068	69.155	58.114	61.528	71.144
	(-314.070)	(-333.821)	(-236.205)	(-264.584)	(-353.208)
Milled rice crude protein (g/100 g dry solids)	61.059	70.526	63.381	59.170	66.847
	(-217.255)	(-289.309)	(-233.972)	(-204.122)	(-260.076)
Apparent amylose content (g/100 g dry solids)	8.371	8.952	12.818	15.247	15.380
	(-66.917)	(-76.289)	(-154.729)	(-218.251)	(-222.043)
Alkali spreading value	106.825	106.202	101.160	79.267	104.997
	(-372.744)	(-368.432)	(-334.424)	(-205.960)	(-360.156)
*Based on Fisher's linear discrimination function.
Values in parentheses are constant (β0). Significances of the discriminate function by Wilks’ Lambda method equal to 0.000.

Table 5  Varietal discrimination results of samples in validation set based on individual physicochemical attribute

Attribute and varieties	n	TP	FP	Sensitivity	Specificity	% Total accuracy
Hundred-grain weight (g dry basis)						65.38
KDML105	33	23	11	0.6765	0.8866
PTT1	25	19	13	0.5938	0.8762
SPR60	20	8	3	0.7273	0.9727
CNT1	25	13	14	0.4815	0.8667
PSL2	27	22	3	0.8800	0.9709
Rough rice moisture content (g/100 g)						30.77
KDML105	33	10	26	0.2778	0.7320
PTT1	25	3	16	0.1579	0.8476
SPR60	20	11	14	0.4400	0.8727
CNT1	25	8	13	0.3810	0.8762
PSL2	27	8	20	0.2857	0.8058
Brown rice crude protein (g/100 g dry solids)						55.38
KDML105	33	22	12	0.6471	0.8763
PTT1	25	6	11	0.3529	0.8952
SPR60	20	12	6	0.6667	0.9455
CNT1	25	19	18	0.5135	0.8286
PSL2	27	13	10	0.5652	0.9029
Milled rice crude protein (g/100 g dry solids)						47.69
KDML105	33	11	13	0.4583	0.8660
PTT1	25	16	3	0.8421	0.9714
SPR60	20	5	13	0.2778	0.8818
CNT1	25	22	26	0.4583	0.7524
PSL2	27	8	12	0.4000	0.8835
Apparent amylose content (g/100 g dry solids)						54.62
KDML105	33	20	15	0.5714	0.8454
PTT1	25	10	13	0.4348	0.8762
SPR60	20	19	2	0.9048	0.9818
CNT1	25	11	15	0.4231	0.8571
PSL2	27	11	13	0.4583	0.8738
Alkali spreading value						52.31
KDML105	33	27	34	0.4426	0.6495
PTT1	25	3	12	0.2000	0.8857
SPR60	20	8	7	0.5333	0.9364
CNT1	25	26	1	0.9630	0.9905
PSL2	27	4	7	0.3636	0.9320
TP: true positive; FP: false positive; Sensitivity: the proportion of correctly classified actual positives that was calculated from the division of the number of true positives by all testing samples number; Specificity: the proportion of correctly classified actual negatives that was calculated from the ratio of the number of true negatives to all testing samples number.

Table 6  Standardized canonical discriminant function coefficients based on calibration samples

	Function
Properties	1	2	3	4
Hundred-grain weight (g dry basis)	−0.300	−0.298	−0.420	−0.017
Brown rice crude protein (g/100 dry solids)	−4.666	0.768	1.010	0.238
Milled rice crude protein (g/100 dry solids)	4.959	−0.020	0.101	0.420
Apparent amylose content (g/100 dry solids)	0.016	−0.600	0.883	−0.111
Alkali spreading value (g/100 dry solids)	0.362	1.104	0.726	−0.386

Table 7  Discriminant coefficients of variety group multiple attributes excluding rough rice moisture content and identification results in validation set

	Identification function coefficients*
Attribute	KDML105	PTT1	SPR60	CNT1	PSL2
Hundred-rough rice weight (g dry basis)	830.8727	708.1769	709.7672	890.0582	741.6108
Brown rice crude protein (g/100 g dry solids)	259.2553	104.5739	−2.06733	180.2293	239.0522
Milled rice crude protein (g/100 g dry solids)	−103.357	92.06089	194.8669	−40.1259	−53.6603
Apparent amylose content (g/100 g dry solids)	14.14344	15.74797	19.15129	21.4284	23.01027
Alkali spreading value	228.0604	256.3647	237.979	171.7532	241.9112
Constant	−2785.2	−2732.65	−2534.9	−2485.92	−3030.8
Correct identification (%)	100	100	100	100	100
Sensitivity	1.00	1.00	1.00	1.00	1.00
Specificity	1.00	1.00	1.00	1.00	1.00
*Based on Fisher's linear discrimination function.
Significance of the discriminate function by Wilks’ Lambda method equal to 0.000.

Figure 1 Discrimination plot of first two functions of rough rice varieties (KDML105, PTT1, SPR60, CNT1 and PSL2) in calibration set based on hundred rough rice weight, brown rice crude protein, milled rice crude protein, apparent amylose content, and alkali spreading value.

Figure 2 Discrimination plot of first two functions of rough rice varieties (KDML105, PTT1, SPR60, CNT1 and PSL2) in validation set based on hundred rough rice weight, brown rice crude protein, milled rice crude protein, apparent amylose content, and alkali spreading value.