Sorption isotherms modeling approach of rice-based instant soup mix stored under controlled temperature and humidity

Figures & data

Table 1. Sorption isotherm models used

S. No.	Model Name	Equation
1	Chung-Pfost	$$M_e=A+B\text{ln}(-ln\left(ERH\right))$$
2	GAB	$$M_e=\frac{ABC(ERH)}{\left(1-C(ERH)\right)\left(1-C(ERH)+BC(ERH)\right)}$$
3	Henderson	$$M_e={\left(-\frac{ln\left(1-ERH\right)}{A}\right)}^{1/B}$$
4	Kuhn	$$M_e=\frac{A}{ln(ERH)}+B$$
5	Oswin	$$M_e=A{\left(\frac{ERH}{1-ERH}\right)}^B$$

Notes: A, B, C are the temperature-dependent product constants; M _e is the equilibrium moisture content (% db); ERH is the equilibrium relative humidity.

Figure 1. Sorption studies of rice-based instant soup mix

Table 2. Statistical parameters for sorption models

Model	Temperature (°C)	Model constants			R ^2	E%	RMSE	χ ^2
		A	B	C
Chung-Pfost	15	7.620	−8.591	–	0.888	28.123	2.557	8.717
	25	6.914	−8.248	–	0.893	28.806	2.396	7.656
	35	6.222	−7.603	–	0.893	29.906	2.210	6.510
	45	5.385	−7.235	–	0.882	34.912	2.219	6.564
GAB	15	4.700	31.309	0.965	0.986	8.919	0.928	1.378
	25	4.373	19.241	0.969	0.990	8.212	0.731	0.855
	35	4.029	15.010	0.968	0.988	9.105	0.743	0.883
	45	3.473	12.138	0.984	0.992	8.332	0.563	0.508
Henderson	15	0.080	0.977	–	0.963	19.344	1.631	3.545
	25	0.096	0.937	–	0.970	18.720	1.407	2.638
	35	0.109	0.922	–	0.971	18.169	1.273	2.161
	45	0.148	0.840	–	0.976	21.202	1.143	1.743
Kuhn	15	−3.754	3.010	–	0.978	8.020	1.130	1.703
	25	−3.607	2.483	–	0.985	6.260	0.905	1.091
	35	−3.321	2.146	–	0.982	6.534	0.895	1.067
	45	−3.194	1.433	–	0.991	4.449	0.606	0.490
Oswin	15	9.031	0.604	–	0.978	13.547	1.164	1.807
	25	8.212	0.627	–	0.985	12.359	0.926	1.142
	35	7.410	0.635	–	0.984	12.668	0.869	1.008
	45	6.349	0.687	–	0.989	13.039	0.713	0.678

Figure 2. Sorption studies of rice-based instant soup mix with curve fitting of GAB model

Figure 3. ln (e.r.h) vs. 1/T graphs for calculating the heat of sorption of rice-based instant soup mix

Figure 4. Variation in net isosteric heat of sorption with moisture content