Measurement and Modeling of Moisture Sorption Isotherm of Litchi (Litchi Chinensis Sonn.)

Figures & data

Table 1 Selected isotherm models for fitting experimental data

No.	Model name	Mathematical expression
1.	Day and Nelson model
2.	Modified Halsey model
3.	Modified Chung-Pfost model
4.	Modified Oswin model
5.	GAB model

Figure 1 Measured sorption isotherms (points) for litchi at the temperature levels of 30, 40, and 50°C.

Table 2 The coefficients of the selected models, reduced mean relative error (RMRE), standard error of estimate (RMSE) and the coefficient of determination (R²) for litchi

Model	Temperature (°C)	Coefficients				RMRE (%)	RMSE (%)	R^2
		b0	b1	b2	b3
Day and Nelson	30, 40, 50	6.95 × 10^−7	1.569446	2.325110	−0.04768	9.1898	6.0813	0.9638
Modified Halsey	30, 40, 50	10.6609	−0.031676	2.417281		6.7559	3.6633	0.9746
Modified Chung-Pfost	30, 40, 50	154.3127	−11.31032	0.033847		7.4331	5.0929	0.9869
Modified Oswin	30, 40, 50	98.6643	−0.829739	3.091631		5.9899	3.5929	0.9874
GAB	30	41.0223	325.7558	0.7749		3.1673	2.9749	0.9869
	40	34.5295	114.3076	0.7887		5.6869	3.3663	0.9464
	50	32.6566	18.1243	0.7723		2.0829	1.8129	0.9848

Figure 2 (a) Predicted and measured sorption isotherms for litchi at the temperature levels of 30, 40, and 50°C (GAB model); and (b) predicted and measured sorption isotherms for litchi at the temperature levels of 30°C, 40°C and 50°C (Modified Oswin model).

Table 3 Characteristic parameters of the GAB model

b10	b20	h1	h2
6.25 × 10^−10	0.884055	16484.28261	−70.10988

Figure 3 (a) Residuals of the predicted equilibrium moisture contents (GAB model); and (b) residuals of the predicted equilibrium moisture contents (Modified Oswin model).

Figure 4 Plot of ln (rh) as a function of 1/T_ab at constant moisture content.

Figure 5 Net isosteric heat of sorption (Q_st ) of litchi for different for different values of equilibrium moisture contents.