Drying kinetics and thermodynamic properties of patawa pulp (Oenocarpus bataua Mart.)

Santos, Dyego da Costa; Costa, Tiago Nascimento da; Franco, Fabiana Braga; Castro, Risle da Costa; Ferreira, João Paulo de Lima; Souza, Marcel Alexandre da Silva; Santos, Johnson Clay Pereira

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Brazilian Journal of Food Technology

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ORIGINAL ARTICLE • Braz. J. Food Technol. 22 • 2019 • https://doi.org/10.1590/1981-6723.30518 copy

Drying kinetics and thermodynamic properties of patawa pulp (Oenocarpus bataua Mart.)

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

The patawa is an Amazonian fruit that, due to its sensory and nutritional properties, has aroused the interest of the scientific community. However, its high moisture content confers high perishability to the fresh product. Thus the convective drying kinetics were studied and the thermodynamic properties of the patawa pulp determined. Drying was carried out at different temperatures (40, 50 and 60 °C) and layer thicknesses (0.3 and 0.6 cm), with a constant air velocity of 1.8 m s^-1. Different thin layer drying models were adjusted to the experimental data. Increasing the air temperature and decreasing the layer thickness increased the moisture removal rate and thus reduced the overall process time. Based on the statistical parameters, the Midilli model was the one that best described the drying kinetics of the samples under all conditions evaluated. The effective diffusion coefficients increased with increase in air temperature, showing magnitudes to the order of 10^-10 m² s^-1, and its temperature dependence was represented by the Arrhenius equation, with the activation energy (Ea) from 32.41 and 40.10 kJ mol^-1 for the thicknesses of 0.6 and 0.3 cm, respectively. The variations in enthalpy (ΔH) and entropy (ΔS) decreased with increasing drying temperature, being lowest in the sample dehydrated in a 0.6 cm layer, while the variation in Gibbs free energy (ΔG) increased with the increase in temperature, being higher when dried in a 0.3 cm layer.

Keywords:
Amazonian fruit; Dehydration; Mathematical modelling; Diffusivity; Activation energy; Enthalpy

Designação	Modelo	Equação
Dois termos	$RX = a exp (- k t) + b exp (- q t)$	(2)
Logarítmico	$RX = a exp (- k t) + c$	(3)
Midilli	$RX = a exp (- {k t}^{n}) + b t$	(4)
Newton	$RX = exp (- k t)$	(5)
Page	$RX = exp (- {k t}^{n})$	(6)

Modelo	Espessura (cm)	Temperatura (°C)	Parâmetros do modelo	R²	DQM	χ² (×10^-4)
Dois termos	0,3	40	a: 0,5264; k: 0,0081; b: 0,5265; q: 0,0081	0,9823	0,0454	23,7062
		50	a: 0,5311; k: 0,0145; b: 0,5299; q: 0,0145	0,9992	0,0094	0,9990
		60	a: 0,5138; k: 0,0189; b: 0,5137; q: 0,0189	0,9885	0,0359	15,0580
	0,6	40	a: 0,4565; k: 0,0061; b: 0,5321; q: 0,0061	0,9955	0,0224	5,7053
		50	a: 0,5070; k: 0,0105; b: 0,5133; q: 0,0105	0,9900	0,0318	11,9468
		60	a: 0,5341; k: 0,0132; b: 0,5342; q: 0,0132	0,9885	0,0370	15,7225
Logarítmico	0,3	40	a: 1,1274; k: 0,0067; c: -0,0927	0,9889	0,0359	14,2922
		50	a: 1,1029; k: 0,0128; c: -0,0578	0,9993	0,0086	0,7912
		60	a: 1,0618; k: 0,0168; c: -0,0500	0,9927	0,0286	9,1599
	0,6	40	a: 0,9953; k: 0,0060; c: -0,0090	0,9964	0,0199	4,3609
		50	a: 1,0369; k: 0,0099; c: -0,0230	0,9939	0,0249	7,0047
		60	a: 1,0955; k: 0,0122; c: -0,0368	0,9908	0,0330	12,0355
Midilli	0,3	40	a: 0,9559; k: 0,0010; n: 1,4051; b: -3,8×10^-5	0,9955	0,0228	5,9802
		50	a: 0,9698; k: 0,0030; n: 1,3389; b: -2,4×10^-5	0,9993	0,0089	0,8783
		60	a: 0,9542; k: 0,0061; n: 1,2533; b: -4,9×10^-5	0,9987	0,0122	1,7467
	0,6	40	a: 0,9830; k: 0,0056; n: 1,0161; b: -0,6×10^-5	0,9974	0,0171	3,3295
		50	a: 0,9793; k: 0,0054; n: 1,1332; b: -1,3×10^-5	0,9968	0,0179	3,7923
		60	a: 0,9703; k: 0,0022; n: 1,3800; b: -0,4×10^-5	0,9986	0,0129	1,9212
Newton	0,3	40	k: 0,0075	0,9779	0,0508	26,6688
		50	k: 0,0135	0,9990	0,0106	1,1464
		60	k: 0,0183	0,9840	0,0423	18,5843
	0,6	40	k: 0,0062	0,9950	0,0236	5,7578
		50	k: 0,0102	0,9891	0,0332	11,4375
		60	k: 0,0122	0,9833	0,0445	20,4381
Page	0,3	40	k: 0,0020; n: 1,2829	0,9933	0,0280	8,3957
		50	k: 0,0042; n: 1,2734	0,9991	0,0103	1,1278
		60	k: 0,0093; n: 1,1695	0,9979	0,0154	2,5425
	0,6	40	k: 0,0067; n: 0,9866	0,9970	0,0182	3,5436
		50	k: 0,0066; n: 1,2734	0,9951	0,0222	5,3436
		60	k: 0,0033; n: 1,3033	0,9980	0,0154	2,5239

Temperatura (°C)	Espessura (cm)	Deff (m² s^-1)	R²
40 °C	0,3	0,5666 × 10^-10	0,9967
40 °C	0,6	2,6943 × 10^-10	0,9981
50 °C	0,3	1,0499 × 10^-10	0,9971
50 °C	0,6	4,6079 × 10^-10	0,9990
60 °C	0,3	1,4245 × 10^-10	0,9962
60 °C	0,6	5,6702 × 10^-10	0,9981

Espessura (cm)	Temp. (°C)	ΔH (kJ mol^-1)	ΔS (kJ mol^-1 K^-1)	ΔG (kJ mol^-1)
0,3	40	37,5008	-0,3130	135,5253
	50	37,4177	-0,3133	138,6569
	60	37,3345	-0,3135	141,7911
0,6	40	29,8025	-0,3246	131,4560
	50	29,7194	-0,3249	134,7034
	60	29,6363	-0,3251	137,9535

Instituto de Tecnologia de Alimentos - ITAL Av. Brasil, 2880, 13070-178 Campinas - SP / Brasil, Tel 55 19 3743-1762 - Campinas - SP - Brazil
E-mail: bjftsec@ital.sp.gov.br

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[1] *Corresponding Author: Dyego da Costa Santos, Instituto Federal de Educação, Ciência e Tecnologia do Acre (IFAC), Departamento de Tecnologia em Agroindústria, Rua Coronel Brandão, 1622, Centro, CEP: 69930-000, Xapuri/AC - Brasil, e-mail: dyego.csantos@gmail.com