Drying temperatures on the functional properties of purple-fleshed sweet potato

Vidal, Herbert Gama; Araujo, Leticia Figueiredo de; Barbosa Junior, José Lucena

doi:10.1590/0103-8478cr20201044

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FOOD TECHNOLOGY • Cienc. Rural 52 (6) • 2022 • https://doi.org/10.1590/0103-8478cr20201044 copy

Drying temperatures on the functional properties of purple-fleshed sweet potato

Efeito das temperaturas de secagem nas propriedades funcionais da batata doce de polpa roxa

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT:

Purple-fleshed sweet potatoes are rich in phenolic compounds, such as anthocyanins, and also exhibit hypoglycemic properties. Anthocyanins are natural antioxidants with the capacity to inhibit or delay injuries caused by free radicals. Drying is one of the most commonly used vegetable preservation methods; although,it has parameters that affect the sensory and physicochemical properties of the final product. The present study assessed the impact of drying temperatures (40, 50, and 60 °C) on the purple-fleshed sweet potato. Cut, unpeeled potato slices of 4 cm in diameter and 3 mm in thickness were dried in an oven with hot air circulation. The effect of the different temperatures on the antioxidant capacity, phenolic compound content, and total and monomeric quantities of anthocyanins in purple sweet potato were measured, and a mathematical model describing the drying kinetics was determined. According to the results observed, the process at 40 °C better preserved the phenolic compounds; however, drying at 50 °C was more efficient for conserving the antioxidant capacity measured by the H + capture method performed by DDPH, and for the total and monomeric quantities of anthocyanins. The mathematical models that best described the kinetic curves were those of Henderson and Pabis, and Page.

Key words:
anthocyanins; bioactive compounds; Henderson and Pabis; Page model; drying kinetics; Ipomoea potatoes

Universidade Federal de Santa Maria Universidade Federal de Santa Maria, Centro de Ciências Rurais , 97105-900 Santa Maria RS Brazil , Tel.: +55 55 3220-8698 , Fax: +55 55 3220-8695 - Santa Maria - RS - Brazil
E-mail: cienciarural@mail.ufsm.br

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[1] E-mail: lucenadta@gmail.com. ^*Corresponding author

------------------------------------------------Data used in the construction of the Drying Kinetic Curve-----------------------------------------------
	--------------Drying at 40 °C-------------			--------------Drying at 50 °C-------------			--------------Drying at 60 °C-------------
Time (min)	Xbs	Xbus	Dimensionless	Xbs	Xbus	Dimensionless	Xbs	Xbus	Dimensionless
0	1.923	0.658	1.000	1.752	0.637	1.000	1.923	0.658	1.000
20	1.455	0.593	0.896	1.252	0.556	0.867	1.122	0.529	0.794
40	1.145	0.534	0.803	0.922	0.480	0.742	0.785	0.440	0.651
60	0.906	0.475	0.710	0.674	0.403	0.616	0.472	0.321	0.461
100	0.613	0.380	0.558	0.374	0.272	0.401	0.248	0.199	0.266
140	0.407	0.289	0.414	0.208	0.172	0.237	0.156	0.135	0.164
180	0.255	0.203	0.277	0.123	0.110	0.135	0.097	0.088	0.089
240	0.148	0.129	0.159	0.068	0.064	0.059	0.068	0.064	0.050
300	0.099	0.090	0.098	0.050	0.048	0.033	0.055	0.052	0.031
360	0.073	0.068	0.062	0.043	0.041	0.022	0.047	0.045	0.020
420	0.056	0.053	0.038	0.039	0.037	0.015	0.043	0.041	0.014
480	0.045	0.043	0.022	0.036	0.035	0.012	0.040	0.039	0.010
1440	0.030	0.029	0.000	0.029	0.028	0.000	0.034	0.033	0.001
1500	0.030	0.029	0.000	0.029	0.028	0.000	0.034	0.033	0.000

Models	--------------------------------------------------Model Designation--------------------------------------------------
Fick - with 6 terms	$Y = \frac{8}{π^{2}} \sum_{i}^{=} \frac{1}{{(2 i + 1)}^{2}} \exp (- {(2 i + 1)}^{2} π^{2} D_{ef} \frac{t}{4 L^{2}})$	(BROOKER et al., 1992BROOKER, D.Bet al. Drying and storage of grains and oilseeds. The AVI Publishing Company, Westport, Connecticut, USA,1992.)	(6)
Henderson; Pabis	$Y = a.exp (- k.t)$	(HENDERSON& PABIS, 1961)	(7)
Page	$Y = \exp (- k. t^{n})$	(PAGE, 1949)	(8)
Peleg	$Y = 1 - \frac{t}{(a + b.t)}$	(PELEG, 1988)	(9)

Model	T (°C)	--------------------------------Parameters-------------------------------				R²	R² (adj)		RMSE	E (%)
		Def	k	n	a	b
Fick	40 °C	3.1675E-10	-	-	-	-	0.9781	0.6781	0.0388	25.0980
	50 °C	4.5273E-10	-	-	-	-	0.9792	0.6792	0.0300	27.4081
	60 °C	5.5245E-10	-	-	-	-	0.9792	0.6792	0.0231	15.5659
Henderson & Pabis	40 °C	-	0.0070	-	1.0376	-	0.9976	0.9143	0.0131	9.1773
	50 °C	-	0.0100	-	1.0463	-	0.9972	0.9138	0.0130	10.5615
	60 °C	-	0.0128	-	1.0167	-	0.9990	0.9157	0.0280	19.2568
Page	40 °C	-	0.0026	1.1859	-	-	0.9996	0.9163	0.0048	2.7007
	50 °C	-	0.0031	1.2389	-	-	0.9997	0.9164	0.0087	6.7135
	60 °C	-	0.0090	1.0752	-	-	0.9993	0.9159	0.0059	6.9479
Peleg	40 °C	-	-	-	110.7582	0.8437	0.9824	0.8991	0.0383	39.2784
	50 °C	-	-	-	75.1932	0.8635	0.9793	0.8960	0.0371	44.9725
	60 °C	-	-	-	53.1257	0.8963	0.9861	0.9027	0.0280	32.7852

Extract	Phenolic Compounds^a	DPPH ^b	Phosphomolybdenum^c	Total Anthocyanins^d	Monomeric Anthocyanins^d
In Natura	11.86 ± 0.33^f	29.81 ± 3.75^f	-	24.86 ± 0.78^f	5.07 ± 0.43^f
Flour 40 °C	32.02 ± 0.52^g	40.97 ± 2.66^g	240.39 ± 50.44^g	38.19 ± 1.02^g	7.67 ± 1.05^g
Flour 50 °C	25.94 ± 0.35^h	56.47 ± 3.08^h	629.52 ± 25.82^h	72.07 ± 2.69^h	14.96 ± 2.46^h
Flour 60 °C	18.24 ± 0.21ⁱ	32.03 ± 3.57^f	929.31 ± 49.15ⁱ	37.09 ± 0.76^g	7.36 ± 0.99^g

Variety name	Anthocyanins^a	Method	References
Stokes Purple	328^b	pH differential	TRUONGet al. (2010TRUONG, V.-D. et al. Characterization of anthocyanins and anthocyanidins in purple fleshed sweet potatoes by HPLC-DAD/ESI-MS/MS. Journal of Agricultural and Food Chemistry , v.58, n.1, 404-410, 2010. Available from: <Available from: https://pubmed.ncbi.nlm.nih.gov/20017481/ >. Accessed: Oct. 29, 2020. doi: 10.1021/jf902799a. https://pubmed.ncbi.nlm.nih.gov/20017481... )
NC 415	178^b
Okinawa	65^b
Shinzami	1342	HPLC	KIMet al. (2012KIM, H. W. et al. Anthocyanin changes in the Korean purple-fleshed sweet potato, Shinzami, as affected by steaming and baking. Food Chemistry , v.130, n.4, p.966-972, 2012. Available from: <Available from: https://www.sciencedirect.com/science/article/abs/pii/S0308814611011630 >. Accessed: Oct. 29, 2020. doi: 10.1016/j.foodchem.2011.08.031. https://www.sciencedirect.com/science/ar... )
12 Variedades da China Central	78 - 695	HPLC	ZHU et al. (2010ZHU, F. et al. Anthocyanins, hydroxycinnamic acid derivatives, and antioxidant activity in roots of different Chinese purple fleshed sweet potato genotypes. Journal of Agricultural and Food Chemistry , v.58 n.13, p.7588-7596, 2010. Available from: <Available from: https://pubmed.ncbi.nlm.nih.gov/20524661/ >. Accessed: Oct. 29, 2020. doi: 10.1021/jf101867t. https://pubmed.ncbi.nlm.nih.gov/20524661... )
NDOP5847-1	175	pH differential	RODRIGUEZ-SAONA et al. (1998RODRIGUEZ-SAONA, L. E. et al. Anthocyanin pigment composition of red-fleshed potatoes. Journal of Food Science, v.63, n.3, p.458-465, 1998.)
P40	1390	HPLC	JIANTENG XUet al. (2015JIANTENG, XU et al. Characterisation and stability of anthocyanins in purple-fleshed sweet potato P40. Food Chemistry , v.186, p.90-96, 2015.)
ILS 16	1112^b	pH differential	VIZZOTTOet al. (2017VIZZOTTO, M. et al. Physicochemical and antioxidant capacity analysis of colored sweet potato genotypes: in natura and thermally processed. Ciência Rural, v.47, 2017. Available from: <Available from: https://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-84782017000400751 >. Accessed: Oct. 29, 2020. doi: 10.1590/0103-8478cr20151385. https://www.scielo.br/scielo.php?script=... )
ILS 56	1072^b
ILS 71	361^b
CNPH 0005	88,6	pH differential	PILON et al. (2020PILON, L., et al. Avaliação físico-química e compostos bioativos de farinhas de batatas-doces de polpa roxa. Brasília: EMBRAPA, 2020. (Boletim de pesquisa e desenvolvimento 202).)
CNPH 0080	60,6
CNPH 1261	57
CNPH 1399	193,8
CNPH 1402	56,2
CNPH 1405	200