Comparison of the Sorption Isotherm Characteristics of Two Cassava Products

Figures & data

Table 1 Initial Composition of the two materials.

	Garifiedwt %	Ungarified wt %
Moisture	13.62	20.50
Carbohydrates	84.27	77.41
Crude Protein	1.03	1.03
Fat	0.25	0.24
Total phosphorus	0.82	0.81
Others	< 0.01	< 0.01

Table 2 Equilibrium moisture contents, g H₂O/100 g solids at different water activities for the two materials.

	Garified			Ungarified
Water activity aw	20°C	30°C	40°C	20°C	30°C	40°C
0.11	4.6	4.34	4.06	3.32	3.01	2.21
0.23	6.23	6.30	5.70	4.68	3.97	3.85
0.33	8.52	8.52	8.30	5.78	5.33	4.96
0.43	9.01	9.28	8.78	6.42	5.91	5.74
0.57	9.88	9.64	9.39	7.17	6.94	6.45
0.67	13.03	12.61	12.42	10.67	10.14	9.55
0.75	16.89	16.23	16.10	14.81	14.34	14.01
0.79	21.93	20.24	19.54	19.42	18.78	18.24
0.93	26.80	25.24	25.02	21.09	20.64	19.40

Figure 1 Comparison of the adsorption isotherms for the two products at 30°C.

Table 3 Estimated parameters by nonlinear regression for GAB, BET, and Modified BET Models—garified product.

	Fitting range, (aw)	XM Monolayer Moisture, g · H2O/100 g solid	C Constant	K Correction factor	r ^2 Correlation coefficient	%RMS
GAB, (°C)	0–0.93
20		5.21	5.44	0.79	0.978	17.79
30		5.26	5.62	0.77	0.978	16.16
40		5.54	5.63	0.73	0.979	16.42
BET, (°C)	0–0.43
20		3.37	7.19		0.998	26.48
30		3.62	8.13		0.994	20.21
40		3.45	6.53		0.998	23.65
Modified BET, (°C)	0–0.75
20		11.25	2.94		0.984	3.87
30		12.25	3.81		0.987	10.63
40		11.98	3.00		0.989	6.88

Table 4 Estimated parameters by nonlinear regression for GAB, BET, and Modified BET models—ungarified product.

	Fitting range, (aw)	XM Monolayer Moisture, g · H2O/100 g solid	C Constant	K Correction factor	r ^2 Correlation coefficient	%RMS
GAB, (°C)	0–0.93
20		12.97	3.55	0.487	0.943	2.70
30		12.97	7.29	0.728	0.954	5.28
40		12.97	5.08	0.422	0.960	4.46
BET, (°C)	0–0.43
20		8.78	1.72		0.971	24.27
30		5.90	1.97		0.948	23.65
40		7.31	1.81		0.956	23.89
Modified BET, (°C)	0–0.75
20		7.21	1.84		0.976	21.05
30		2.94	2.94		0.986	16.46
40		5.65	1.44		0.991	19.19

Table 5 Excess heat of sorption, kJ/mol as a function of moisture content for both materials.

Moisture Content g H2O/g solids	Garified material	Ungarifeid material
1	39.47	26.98
3	38.60	25.25
5	34.23	21.17
6	30.26	18.46
8	21.23	13.47
10	14.57	10.11
11	12.34	8.96
13	9.30	7.33
15	7.41	6.27
16	6.72	5.87
18	5.78	5.24
20	4.92	4.79

Table 6 Estimated shelf-life (days) for safe storage at a_w 0.7 at different initial moisture content, (dry basis) for the garified product.

Initial moisture content, % (d.b)	20°C	30°C	40°C
5	209	148	86
8	163	65	53
10	85	58	37
12	54	38	20

Table 7 Estimated shelf-life (days) for safe storage at a_w 0.7 at different initial moisture content, (dry basis) for the ungarified product.

Initial moisture content, % (d.b)	20°C	30°C	40°C
5	169	121	73
8	123	53	38
10	52	37	22
12	27	18	8