Possibilities of Using Electrical Parameters of Milk for Assessing its Adulteration with Water

Figures & data

Figure 1 Scheme of a measuring system of electric properties of food products: Z–impedance, R–resistance, C_s–equivalent serial capacitance, C_p–equivalent parallel capacitance, M–measuring device.[15]

Table 1 The values of electrical parameters of raw milk and distilled water applied for milk dilution

		Conductance parameters				Capacitance parameters
Experimental material	Statistical measure	Z [Ω]	Y [mS]	R [Ω]	G [mS]	Cp [μF]	Cs [μF]
Raw milk		92.245	10.843	91.986	10.830	1.243	240.875
	V [%]	1.679	1.661	1.661	1.624	9.879	9.675
		Z [kΩ]	Y [μS]	R [kΩ]	G [μS]	Cp [nF]	Cs [μF]
Distilled water		150.974	7.831	151.027	7.832	0.018	9.889
	V [%]	36.227	47.771	36.213	47.773	9.128	87.864
Table 1–2 explanation: Z–impedance, Y–admittance, R–resistance, G–conductance, Cs –equivalent serial capacitance, Cp –equivalent parallel capacitance, –mean value, V–coefficient of variation.

Table 2 Changes of electrical parameters of experimental milk dependently percentage addition of distilled water

		Conductance parameters				Capacitance parameters
Addition of water [%]	Statistical measure	Z [Ω]	Y [mS]	R [Ω]	G [mS]	Cp [μF]	Cs [μF]
0		91.674	10.914	91.331	10.881	1.407	212.032
	V [%]	1.672	1.658	1.657	1.662	10.850	11.144
2		92.275	10.842	91.951	10.809	1.373	218.564
	V [%]	1.691	1.682	1.679	1.695	9.672	9.735
4		93.400	10.712	93.097	10.682	1.303	224.734
	V [%]	1.799	1.790	1.781	1.804	9.461	9.905
6		94.673	10.568	94.381	10.540	1.255	227.128
	V [%]	1.945	1.937	1.931	1.946	10.006	10.870
8		95.706	10.452	95.428	10.428	1.201	232.794
	V [%]	1.805	1.781	1.783	1.815	10.642	11.263
10		97.361	10.272	97.121	10.248	1.154	233.801
	V [%]	1.709	1.685	1.677	1.703	10.103	10.590
15		100.583	9.948	100.338	9.929	1.070	235.777
	V [%]	2.273	2.330	2.275	2.346	10.641	10.389
20		105.275	9.503	105.025	9.484	0.978	235.199
	V [%]	1.634	1.624	1.611	1.638	9.436	9.823
25		109.842	9.110	109.612	9.094	0.874	251.586
	V [%]	2.200	2.154	2.181	2.165	10.424	23.542
30		114.784	8.716	114.556	8.703	0.815	237.397
	V [%]	1.907	1.870	1.884	1.888	8.941	10.186
35		121.729	8.219	121.505	8.208	0.726	232.150
	V [%]	1.857	1.850	1.846	1.856	9.775	13.102
40		128.564	7.782	128.349	7.772	0.656	235.694
	V [%]	1.909	1.864	1.895	1.875	8.272	9.571

Figure 2 Mathematical dependence between percentage water addition (W) to experimental milk in function of admittance, at 100 Hz frequency measured.

Table 3 Regression analysis of percentage water addition (W) to experimental milk in function of electrical parameters (Z, Y, R, G, C _p , C _s )

Electrical parameters	r	α	Regression equations
Z	0.989	0.000**	W [%] = − 96.478 + 1.086 × Z
Y	- 0.998	0.000**	W [%] = 139.200 – 12.606 × Y
R	0.990	0.000**	W [%] = − 95.900 + 1.083 × R
G	- 0.998	0.000**	W [%] = 139.823 – 12.698 × G
Cp	- 0.995	0.000**	W [%] = 72.623 – 52.800 × Cp
Cs	0.764	0.003**	W [%] = − 271.947 + 1.250 × Cs
Table 3 explanation: α–significance level–calculated, r–correlation coefficient, **–correlation significance, α < 0.01.

Table 4 The results of calculation of water content in full fat milk on the basis of determined regression equations for selected electrical parameters

	Water added to full fat milk on the basis of determined regression equations (Table 3):
Real amount of water added [%]	Z	Y	Cp	Cs
0	3.08	1.62	1.67	6.91
2	3.73	2.53	0.13	1.26
4	4.95	4.16	3.82	8.97
6	6.34	5.98	6.36	11.96
8	7.46	7.44	9.21	19.04
10	9.26	9.71	11.69	20.30
15	12.76	13.80	16.13	22.77
20	17.85	19.41	20.98	22.05
25	22.81	24.36	26.48	42.54
30	28.18	29.33	29.59	24.80
35	35.72	35.59	34.29	18.24
40	43.14	41.10	37.99	22.67

Żywica , R. , Pierzynowska–Korniak , G. and Wójcik , J. 2005 . Application of food products electrical model parameters for evaluation of apple purée dilution . Journal of Food Engineering , 67 : 413 – 418 .

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