Microwave-vacuum drying of pulsed vacuum osmotic dehydration-pretreated Yacon as an alternative for preserving fructo-oligosaccharides

Lopes, Francemir José; Corrêa, Jefferson Luiz Gomes; Petri Júnior, Irineu; Mello Júnior, Ronaldo Elias de; Souza, Amanda Umbelina de; Corona-Jiménez, Edith; Pereira, Michel Cardoso de Ângelis

doi:10.1590/1413-7054202448015523

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Food Science and Technology • Ciênc. agrotec. 48 • 2024 • https://doi.org/10.1590/1413-7054202448015523 copy

Microwave-vacuum drying of pulsed vacuum osmotic dehydration-pretreated Yacon as an alternative for preserving fructo-oligosaccharides

Secagem por microondas a vácuo de Yacon pré-tratado por desidratação osmótica pulsada como alternativa de preservação de fruto-oligosacarídeos

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

Yacon, a perennial plant from the Andean region, is particularly rich in fructo-oligosaccharides (FOS) and inulin. However, these saccharides are rapidly hydrolyzed after harvest, affecting the functional characteristics of yacon. Therefore, a preservation technology such as drying is warranted to preserve the FOS content of yacon products during the off-season. To this end, we dried yacon slices, either untreated or pretreated with pulsed vacuum osmotic dehydration (PVOD), in a microwave vacuum (MWV). PVOD was performed using a sorbitol solution (38 °Brix, 35 °C, and 681 mmHg during the first 10 min). A three-level experimental design with three initial power densities (PDs) of 3.6, 6.3, and 9.9 W.g⁻¹ and three vacuum pressures (VPs) of 0, 300, and 600 mmHg was employed to perform the MWV drying experiments. FOS content, drying kinetics, diffusivity, shrinkage, yacon temperature, and rehydration were investigated. We observed that during PVOD, as microwave PD increased, the drying time, moisture, and water activity decreased. Moreover, an increase in PD positively affected FOS retention, diffusivity, temperature, and shrinkage. Furthermore, VP significantly affected FOS retention in pretreated samples and facilitated drying. In addition, microwaves with a higher PD increased the effective diffusivity and facilitated FOS retention. VP also affected the drying and FOS retention of pretreated samples. In general, yacon browning was observed under all treatment conditions, independent of pretreatment. For osmotically dehydrated samples, processing conditions with a PD of 9.9 W.g⁻¹ and vacuum pressure of 600 mmHg are ideal for drying yacon slices via microwave vacuum, thereby increasing the FOS content by approximately 40%.

Index terms:
Pulsed vacuum osmotic dehydration; prebiotic; fructo-oligosaccharides; tubercle; fructans.

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[1] *Corresponding author: irineu.junior@ufla.br

Assay	Content of fructans [%, d.b]		Retention of fructans [%]
Assay	Without PVOD	With PVOD^*	Without PVOD	With PVOD
1	29.20	43.32	46.15	68.47
2	19.73	50.97	31.19	80.56
3	17.95	55.37	28.37	87.53
4	28.87	54.85	45.64	86.70
5	33.91	52.75	53.59	83.38
6	44.87	60.57	70.98	95.74
7	51.04	54.68	80.68	86.43
8	40.63	59.16	64.22	93.51
9	42.87	59.87	67.77	94.64

Assay	∆E	h^°	C^*	L ^*
Assay	Without PVOD
1	5.99	76.39	16.34	50.15
2	5.52	75.73	21.16	54.59
3	6.52	84.73	21.62	55.11
4	8.68	73.82	14.21	46.38
5	6.26	74.04	19.18	52.01
6	8.37	79.78	19.66	60.58
7	7.23	69.26	14.76	47.87
8	5.36	73.61	17.53	51.41
9	5.92	77.11	19.39	55.81
	With PVOD
1	10.95	72.43	11.23	55.81	44.33
2	10.48	64.88	12.66	45.06
3	6.72	69.21	17.28	49.48
4	9.72	76.49	11.52	45.28
5	10.08	67.09	12.98	44.98
6	9.89	73.34	13.69	45.07
7	13.69	65.88	10.94	41.83
8	13.70	63.60	12.52	41.29
9	12.41	66.03	12.28	42.87

Assay	Shrinkage [%]
Assay	Without PVOD	With PVOD
1	81.16	60.32
2	81.88	62.59
3	72.12	55.75
4	73.90	51.88
5	74.22	50.25
6	70.27	53.04
7	67.47	48.83
8	64.43	46.15
9	65.06	40.11

Assay	Drying time [min]
Assay	Without PVOD	Water activity (a _w )	With PVOD	Water activity (a _w )
1	130.0	0.480±0.055	95.2	0.485±0.026
2	96.8	0.539±0.017	77.8	0.367±0.038
3	81.7	0.560±0.004	67.0	0.376±0.062
4	38.8	0.552±0.021	36.8	0.474±0.064
5	45.7	0.551±0.289	35.5	0.498±0.009
6	35.7	0.533±0.022	27.0	0.460±0.069
7	32.2	0.573±0.019	22.0	0.472±0.021
8	31.0	0.554±0.053	21.8	0.485±0.043
9	28.5	0.549±0.031	12.3	0.407±0.097

Without PVOD
Assay	Without shrinkage				With shrinkage
Assay	D_eff [m²s^-1]	R²	RSME	χ²	D_eff [m²s^-1]	R²	RSME	χ²
1	1.05x10^-10	0.894	0.102	0.017	3.15 x10^-10	0.917	0.062	0.017
2	1.32 x10^-10	0.904	0.097	0.003	4.69 x10^-10	0.963	0.060	0.011
3	1.99 x10^-10	0.916	0.094	0.001	8.16 x10^-10	0.965	0.061	0.009
4	2.21 x10^-10	0.807	0.101	0.017	6.01 x10^-10	0.917	0.013	0.020
5	2.04 x10^-10	0.779	0.165	0.009	7.59 x10^-10	0.924	0.097	0.011
6	3.03 x10^-10	0.887	0.171	0.004	1.36 x10^-9	0.938	0.128	0.008
7	3.31 x10^-10	0.758	0.194	0.004	1.04 x10^-9	0.921	0.111	0.010
8	3.43 x10^-10	0.809	0.164	0.003	1.99 x10^-9	0.841	0.149	0.002
9	3.21 x10^-10	0.713	0.215	0.015	1.06 x10^-9	0.877	0.141	0.018
With PVOD
1	1.06 x10^-10	0.853	0.120	0.009	3.00 x10^-10	0.922	0.050	0.007
2	1.36 x10^-10	0.832	0.138	0.008	3.08 x10^-10	0.974	0.054	0.007
3	1.22 x10^-10	0.746	0.176	0.017	3.60 x10^-10	0.950	0.078	0.007
4	2.29 x10^-10	0.750	0.110	0.011	6.42 x10^-10	0.922	0.100	0.008
5	2.28 x10^-10	0.841	0.202	0.014	6.49 x10^-10	0.907	0.114	0.011
6	3.53 x10^-10	0.999	0.002	0.001	9.88 x10^-10	0.854	0.101	0.001
7	3.87 x10^-10	0.814	0.141	0.002	1.08 x10^-9	0.982	0.043	0.001
8	3.94 x10^-10	0.749	0.183	0.009	1.55 x10^-9	0.852	0.140	0.008
9	8.98 x10^-10	0.914	0.094	0.003	3.26 x10^-9	0.974	0.051	0.002

Assay	Coded variables		Actual variables
	X₁	X₂	PD [Wg^-1]	VP [mmHg]
1 (Without PVOD)	-1	-1	3.6	0^*
2 (Without PVOD)	-1	0	3.6	300
3 (Without PVOD)	-1	1	3.6	600
4 (Without PVOD)	0	-1	6.3	0^*
5 (Without PVOD)	0	0	6.3	300
6 (Without PVOD)	0	1	6.3	600
7 (Without PVOD)	1	-1	9.9	0^*
8 (Without PVOD)	1	0	9.9	300
9 (Without PVOD)	1	1	9.9	600
1 (With PVOD)	-1	-1	3.6	0^*
2 (With PVOD)	-1	0	3.6	300
3 (With PVOD)	-1	1	3.6	600
4 (With PVOD)	0	-1	6.3	0^*
5 (With PVOD)	0	0	6.3	300
6 (With PVOD)	0	1	6.3	600
7 (With PVOD)	1	-1	9.9	0^*
8 (With PVOD)	1	0	9.9	300
9 (With PVOD)	1	1	9.9	600

Parameters	Predicted values
FOS retention [%]	98.717
Time [min]	10.77
Shrinkage [%]	44.85
C^*	14.37
h^°	68.8
L ^*	42.32
∆E	12.79

Without PVOD
Factor	Drying time		Retention fructans		Shrinkage		∆E		h^°		C^*		L ^*
Factor	RE	p	RE	p	RE	p	RE	p	RE	p	RE	p	RE	p
M/I	400.67	0.003	54.28	0.00	72.28	0.00	6.82	0.00	76.05	2.5 x 10^-11	19.29	1.05 x10^-7	52.66	1.9 x 10^-11
PD (L)	-361.33	0.001	17.83	0.00	-6.37	0.002	-	-	-2.81	0.01	-1.24	0.01	-	-
PD (Q)	266.33	0.042	-	-	-	-	-1.66	0.01	-	-	-	-	-	-
VP (L)	-	-	-	-	-	-	-	-	3.69	0.00	2.56	0.00	4.52	-
VP (Q)	-	-	-	-	-	-	1.40	0.01	-	-	-1.63	0.03	-	-
R²	0.951	-	0.764	-	0.764	-	0.833		0.851		0.951		0.799
With PVOD
M/I	331.00	0.0001	86.33	0.00	52.11	0.00	10.85	0.00	68.73	0.00	12.79	0.00	44.47	0.00
PD (L)	-306.50	0.0000	6.34	0.01	-7.26	0.001	1.94	0.02	-	-	-	-	-2.15	0.02
PD (Q)	162.50	0.0078	-	-			-	-	-5.30	0.03	-	-	-	-
VP (L)	-79.50	0.0150	6.05	0.01			-	-	-	-	1.58	0.03	-	-
VP (Q)	-	-	-	-			-	-	5.37	0.03	-	-	-	-
R²	0.978	-	0.806	-	0.822		0.785		0.757		0.750		0.797

Statistical parameters Drying time Retention fructans		Without PVOD
Statistical parameters Drying time Retention fructans		Shrinkage	∆E	h°	C^*	L ^*
SS Error Total	Regression	9252.38	1906.61	243.20	9.42	129.16	53.81	122.71
	1280.58	693.58	75.11	1.88	22.51	2.79	30.77
	10532.96	2600.19	318.31	11.29	151.67	2.79	153.49
df Error Total	Regression	2	1	1	2	2	3	1
	6	7	7	6	6	5	7
	8	8	8	8	8	8	8
MS Error	Regression	4626.19	1906.61	243.20	4.72	64.58	17.94	122.71
MS Error	213.43	99.08	10.73	0.31	3.75	0.56	4.4
F_cal	Regression	21.68	19.24	22.66	14.99	17.22	32.15	27.91
p-value	Regression	0.001	0.003	0.002	0.00	0.00	0.00	0.00
F _tab 0.05%	Regression	5.14	5.59	5.59	5.14	5.14	5.41	5.59
R²		0.950	0.764	0.764	0.833	0.851	0.950	0.799
		With PVOD
SS Error Total	Regression	6543.87	460.71	316.44	22.66	113.91	15.07	27.61
	143.78	111.20	68.78	16.04	40.62	13.36	18.72
	6687.66	571.99	385.23	38.7	154.52	28.42	46.31
df Error Total	Regression	3	2	1	1	2	1	1
	5	6	7	7	6	7	7
	8	8	8	8	8	8	8
MS Error	Regression	2181.29	230.35	316.44	22.66	56.95	15.07	27.61
MS Error	28.76	18.53	9.83	2.29	6.77	1.91	2.67
F_cal	Regression	75.85	12.429	32.20	9.89	8.41	7.92	10.33
p-value	Regression	0.00	0.007	0.0007	0.02	0.016	0.03	0.01
F _tab 0.05%	Regression	5.41	5.14	5.59	5.59	5.14	5.59	5.59
R²		0.978	0.806	0.821	0.785	0.757	0.751	0.797