Dielectric properties of guava, mamey sapote, prickly pears, and Nopal in the microwave range

Figures & data

Table 1. Average physicochemical parameters of studied fruits and no pal.

Sample	pH	Total soluble solids (ºBx)	Titratable acidity	Maturity Index
Guava unripe	3.60 ± 0.010	11.9 ± 0.07	0.79 ± 0.02% citric acid	15.06
Guava ripe	3.86 ± 0.007	12.2 ± 0.07	0.66 ± 0.01% citric acid	18.48
Mamey sapote unripe	5.91 ± 0.010	25.0 ± 0.28	0.07 ± 0.003 % malic acid	357.14
Mamey sapote ripe	6.06 ± 0.007	33.0 ± 1.34	0.04 ± 0.004 % malic acid	825.0
Red prickly pear unripe	6.17 ± 0.007	10.6 ± 0.10	0.20 ± 0.01% citric acid	53.0
Red prickly pear ripe	6.23 ± 0.021	12.0 ± 0.07	0.19 ± 0.01% citric acid	63.15
White prickly pear unripe	6.08 ± 0.007	10.9 ± 0.07	0.05 ± 0.005% citric acid	272.50
White prickly pear ripe	6.11 ± 0.007	12.0 ± 0.07	0.04 ± 0.005% citric acid	300.0
Nopal	4.37 ± 0.007	3.6 ± 0.10	NA	NA

NA: Not applicable.

Table 2. Average dielectric constant (ε’), dielectric loss factor (ε”), and penetration depth (d_p) of guava and mamey sapote fruits, ripe, and unripe stages, at ISM (Industrial, Scientific and Medical) frequencies.

		Guava ripe			Guava unripe			Mamey Sapote ripe			Mamey Sapote unripe
T (°C)	Frequency (MHz)	915	2450	5800	915	2450	5800	915	2450	5800	915	2450	5800
20	‘	67.02	63.5	55.3	65.7	61.8	53.0	67.1	62.4	54.2	66.14	60.66	50.8
	‘‘	12.9	15.10	22.4	16.5	16.6	24.2	17.8	16.5	20.2	20.7	19.09	24.0
	dp (cm)	3.32	1.03	0.27	2.58	0.93	0.25	2.26	0.94	0.3	1.93	0.807	0.25
40	‘	65.0	61.5	53.3	63.7	59.8	51.0	64.8	60.2	52.27	63.9	58.3	48.6
	‘‘	13.8	12.6	19.4	17.8	14.8	19.0	17.24	15.8	19.3	24.2	19.3	22.5
	dp (cm)	2.86	1.21	0.31	2.2	1.02	0.31	2.3	0.96	0.31	1.63	0.78	0.25
60	‘	62.9	59.6	41.4	61.9	58.0	49.2	62.2	57.7	50.0	61.7	55.5	45.4
	‘‘	14.9	11.8	16.5	19.0	14.8	17.6	16.5	15.2	18.3	21.1	18.3	21.1
	dp (cm)	2.80	1.28	0.33	2.18	1.00	0.33	2.33	0.98	0.31	1.84	0.8	0.26

Table 3. Average dielectric constant (ε’), dielectric loss factor (ε”), and penetration depth (d_p) of prickly pear (or cactus pear fruit), white and red variety, ripe, and unripe stages, at ISM (Industrial, Scientific and Medical) frequencies.

		White prickly pear ripe			White prickly pear unripe			Red prickly pear ripe			Red prickly pear unripe
T (°C)	Frequency (MHz)	915	2450	5800	915	2450	5800	915	2450	5800	915	2450	5800
20	‘	80.6	74.4	63.78	70.9	68.73	62.85	73.25	70.6	62.5	69.02	66.2	58.3
	‘‘	9.7	14.3	24.6	8.44	11.18	19.9	9.32	14.15	23.71	10.4	13.88	22.81
	dp (cm)	4.54	1.18	0.27	4.80	1.45	0.32	4.5	1.16	0.27	3.9	1.14	0.27
40	‘	78.10	71.96	61.3	68.43	66.44	60.70	71.45	68.89	61.12	66.02	63.2	55.30
	‘‘	10.8	12.55	20.16	10.17	11.26	18.55	9.7	13.62	22.71	9.21	12.8	21.81
	dp(cm)	3.97	1.32	0.32	3.98	1.41	0.34	4.27	1.19	0.28	4.61	1.20	0.28
60	‘	75.52	69.21	58.5	67.63	65.24	59.9	69.05	66.6	58.9	64.02	61.2	53.3
	‘‘	10.84	10.08	15.13	9.04	9.57	15.6	9.7	13.15	21.82	8.21	11.7	20.61
	dp(cm)	3.90	1.60	0.41	4.44	1.64	0.40	4.19	1.21	0.30	4.76	1.31	0.30

Table 4. Average dielectric constant (ε’), dielectric loss factor (ε”), and penetration depth (d_p) of nopal (cladode from Opuntia) at ISM (Industrial, Scientific, and Medical) frequencies.

		Nopal
T (°C)	Frequency (MHz)	915	2450	5800
20	‘	68.2	66.1	58.9
	‘‘	17.8	13.3	21.4
	dp (cm)	2.27	1.19	0.3
40	‘	66.0	64.0	56.8
	‘‘	16.9	14.0	18.6
	dp (cm)	2.35	1.11	0.33
60	‘	64.1	61.8	54.3
	‘‘	19.9	13.5	15.4
	dp (cm)	1.98	1.14	0.4

Figure 1. Dielectric constant of (a) guava, (b) mamey, and (c) prickly pears and nopal at 20ºC.

Figure 2. Decreasing in dielectric constant due to increasing temperature for unripe fruits: (a) guava, (b) mamey sapote, and (c) red prickly pear.

Figure 3. Dielectric loss factor of (a) guava, (b) mamey sapote, and (c) red prickly pear and nopal at 20ºC.

Figure 4. Decreasing in dielectric loss factor due to increasing temperature for unripe fruits: (a) guava, (b) mamey sapote, and (c) nopal.