Dynamic Isopiestic Method (DIM): Measuring Moisture Sorption Isotherm of Freeze-Dried Garlic Powder and Other Potential Uses of DIM

Figures & data

Figure 1 Schematic flow diagram of a dynamic isopiestic method used in SGA–100.

Table 1 Adsorption moisture isotherm data of garlic by isopiestic and SGA methods.

Adsorption		Symmetrical Gravimetric Analyzer (SGA)
Isopiestic ^a 20°C		10°C		20°C		40°C		60°C
aw	%Xw	aw	%Xw	aw	%Xw	aw	%Xw	aw	%Xw
0.113	5.91 (0.32)	0.05	2.45	0.05	2.57 (0.15)	0.05	2.80 (0.14)	0.05	3.03 (0.47)
0.216	7.46 (0.44)	0.10	3.15	0.10	3.18 (0.18)	0.10	3.61 (0.22)	0.10	3.91 (0.31)
0.336	7.40 (0.33)	0.15	3.58	0.15	3.85 (0.14)	0.15	4.26 (0.02)	0.15	4.35 (0.63)
0.431	9.49 (0.45)	0.20	4.17	0.20	4.55 (0.18)	0.20	4.99 (0.13)	0.20	4.47 (0.50)
0.529	12.00 (0.56)	0.25	4.77	0.25	5.33 (0.18)	0.25	5.77 (0.14)	0.25	5.02 (0.77)
0.577	13.49 (0.41)	0.30	5.76	0.30	6.01 (0.10)	0.30	6.55 (0.24)	0.30	6.02 (0.49)
0.708	19.35 (0.62)	0.35	6.74	0.35	6.93 (0.21)	0.35	7.33 (0.14)	0.35	6.94 (0.75)
0.877	27.22 (0.68)	0.40	7.84	0.40	7.99 (0.25)	0.40	8.33 (0.32)	0.40	7.31 (0.46)
0.985	33.87 (0.86)	0.45	9.05	0.45	9.10 (0.35)	0.45	9.01 (0.22)	0.45	8.14 (0.56)
		0.50	10.35	0.50	10.45 (0.27)	0.50	10.59 (0.48)	0.50	10.27 (0.12)
		0.55	12.03	0.55	12.06 (0.32)	0.55	12.03 (0.22)	0.55	11.60 (0.76)
		0.60	13.88	0.60	13.78 (0.40)	0.60	13.27 (0.26)	0.60	12.90 (0.80)
		0.65	15.47	0.65	15.63 (0.36)	0.65	15.47 (0.36)	0.65	14.25 (1.33)
		0.70	17.82	0.70	17.64 (0.48)	0.70	16.91 (0.41)	0.70	16.12 (1.50)
		0.75	20.69	0.75	20.50 (0.76)	0.75	19.87 (0.47)	0.75	19.33 (0.79)
		0.80	22.29	0.80	23.30 (0.46)	0.80	22.93 (0.63)	0.80	22.19 (0.76)
		0.85	27.54	0.85	27.40 (2.85)	0.85	26.56 (0.49)	0.85	26.17 (1.36)
		0.90	29.75	0.90	33.64 (1.46)	0.90	32.58 (2.14)	0.90	31.71 (2.15)
Desorption		10°C		20°C		40°C		60°C
		aw	%Xw	aw	%Xw	aw	%Xw	aw	%Xw
		0.05	14.43	0.05	13.55 (1.52)	0.05	9.88 (0.94)	0.05	7.37 (0.65)
		0.10	14.66	0.10	13.67 (1.52)	0.10	10.23 (0.72)	0.10	7.33 (0.36)
		0.15	14.64	0.15	13.80 (1.44)	0.15	10.41 (0.83)	0.15	7.16 (0.77)
		0.20	15.15	0.20	13.90 (1.40)	0.20	10.48 (0.75)	0.20	7.25 (1.15)
		0.25	15.30	0.25	13.99 (1.37)	0.25	10.88 (0.53)	0.25	7.60 (1.20)
		0.30	15.63	0.30	14.11 (1.31)	0.30	10.94 (0.74)	0.30	8.03 (1.10)
		0.35	15.91	0.35	14.25 (1.27)	0.35	11.32 (0.73)	0.35	8.59 (0.84)
		0.40	16.22	0.40	14.46 (1.17)	0.40	11.60 (0.65)	0.40	8.79 (0.50)
		0.45	16.30	0.45	14.67 (1.70)	0.45	12.05 (0.77)	0.45	9.69 (1.02)
		0.50	16.94	0.50	15.02 (0.92)	0.50	12.77 (0.39)	0.50	10.56 (1.29)
		0.55	17.53	0.55	15.66 (0.85)	0.55	13.53 (0.57)	0.55	11.49 (0.50)
		0.60	17.56	0.60	16.34 (0.96)	0.60	14.50 (0.72)	0.60	12.73 (0.26)
		0.65	17.85	0.65	17.41 (1.20)	0.65	16.10 (0.70)	0.65	14.71 (0.62)
		0.70	19.55	0.70	19.51 (1.37)	0.70	17.99 (0.28)	0.70	15.42 (2.63)
		0.75	24.61	0.75	22.22 (1.85)	0.75	21.06 (0.66)	0.75	17.82 (1.25)
		0.80	28.64	0.80	25.15 (1.43)	0.80	24.55 (0.50)	0.80	21.54 (0.87)
		0.85	29.91	0.85	29.55 (1.16)	0.85	28.76 (1.04)	0.85	26.44 (1.09)
		0.90	29.75	0.90	33.64 (1.46)	0.90	32.58 (2.14)	0.90	31.71 (2.15)
^aAl-Waili et al.[10]; %Xw : kg water/100 kg sample.

Figure 2 Comparisons with data from Pezzutti and Crapiste.[19]

Figure 3 Moisture adsorption isotherms of freeze-dried garlic powder measured by static and dynamic isopiestic methods.

Figure 4 Moisture adsorption isotherms of freeze dried garlic powder as a function of temperature measured by dynamic method.

Figure 5 Moisture desorption isotherms of freeze dried garlic powder as a function of temperature measured by dynamic method.

Figure 6 Moisture sorption hysteresis of freeze-dried garlic powder at 20°C.

Figure 7 Moisture sorption hysteresis of freeze-dried garlic powder at 60°C.

Table 2 Model parameters for BET, GAB, and Norrish.

BET (aw : 0.05–0.4)
Adsorption					Desorption
T (°C)	Mb	B		MSE	Mb	B		MSE
10°C	0.062	6.29		2.7 × 10^−5	0.101	−62.40		2.4 × 10^−4
20°C	0.061	7.92		1.5 × 10^−5	0.107	−58.14		3.2 × 10^−4
40°C	0.059	11.84		8.8 × 10^−6	0.082	−73.02		1.0 × 10^−4
60°C	0.050	21.15		1.5 × 10^−6	0.059	−78.91		7.9 × 10^−6
GAB (aw : 0.05–0.9)
T (°C)	Mg	C	K	MSE	Mg	C	K	MSE
10°C	0.125	1.750	0.841	9.8 × 10^−5	0.112	−110.90	0.706	2.9 × 10^−4
20°C	0.084	3.661	0.937	3.0 × 10^−5	0.100	−54.83	0.885	4.3 × 10^−4
40°C	0.077	5.464	0.940	2.7 × 10^−5	0.081	−71.97	0.929	1.3 × 10^−4
60°C	0.073	5.012	0.943	6.0 × 10^−5	0.061	−98.50	0.967	3.5 × 10^−5
Norrish (aw : 0.05–0.9)
T (°C)	E	k		MSE	E	k		MSE
10°C	0.054	−2.855		4.5 × 10^−4	−0.056	−8.19		9.3 × 10^−3
20°C	0.052	−3.276		1.9 × 10^−4	−0.044	−11.62		1.1 × 10^−2
40°C	0.045	−4.787		1.1 × 10^−4	−0.015	−79.86		5.3 × 10^−3
60°C	0.042	−4.774		5.9 × 10^−4	0.006	−270.50		3.6 × 10^−3
Mb and Mg : kg water/kg solids.

Al-Waili , N.S. , Rahman , M.S. and Sablani , S.S. 2005 . Moisture adsorption isotherm of freeze-dried garlic powders . Proceedings of the International Conference on Postharvest Technology and Quality Management in Arid Tropics held in Sultan Qaboos University . 31 January–2 February 2005 , Muscat, Sultanate of Oman.

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Pezzutti , A. and Crapiste , G.H. 1997 . Sorption equilibrium and drying characteristics of garlic . Journal of Food Engineering , 31 : 113 – 123 . [CROSSREF]

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