Solubility of Trehalose in Water + Ethanol Solvent System from

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Solubility of Trehalose in Water + Ethanol Solvent System from (288.15 to 318.15) K Peng Wang,*,†,‡ Jinxia Jiang,† Xiao’an Jia,† Linjie Jiang,‡,§ and Suye Li‡,§ †

School of Chemical Engineering, Changchun University of Technology, Changchun, Jilin 130012, People’s Republic of China Advanced Institute of Materials Science, Changchun University of Technology, Changchun, Jilin 130012, People’s Republic of China

‡

ABSTRACT: The solubility of trehalose in a water + ethanol solvent system was measured with the mole fraction of water ranging from 0.000 to 1.000 at temperatures from (288.15 to 318.15) K using the gravimetric method. There was a minimum point on each solubility curve at the mole fraction of water ranging from 0.040 to 0.050. The differential scanning calorimetry measurement results show that anhydrous trehalose (a white flocculent precipitate) appeared in the suspension at water content lower than the critical point. While higher than that point, the crystals in the slurry were still hydrous polymorph which is apparently different from the anhydrous one. The solubility data at water content lower and higher than the critical points were nonlinear surface fitted separately using the combination version of the Jouyban-Acree and van’t Hoff models which is a three-dimensional (3D) model. The average relative deviation (ARD) values for trehalose solubility at water content lower and higher than the critical point were 25.71 % and 11.62 %, respectively, which shows the model fitted the data well especially for the latter.

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INTRODUCTION Trehalose, also known as mycose or tremalose, is a functional sugar, which is a nonreducing disaccharide in which the two αglucose units are linked by a 1,1-glycoside bond, widely found in plants and animals in nature.1 The creatures that can survive in harsh environments have rich trehalose in their bodies. There are two kinds of polymorphs for trehalose, dihydrate and anhydrous, depending on the given thermodynamic conditions. Dihydrate trehalose is the most stable and easily obtained one. The anhydrous trehalose can be observed during the phase transition by different dehydration methods, including the α-, β-, γ-, and ε-forms obtained by different kinds of thermal treatments,2 and the porous anhydrous trehalose crystals obtained by the solvent method, typically in the low water content ethanol solvent mixtures.3 Detailed solubility data of trehalose not only can be used for the design of the crystallization process for dihydrate trehalose, but also for the deep studies of trehalose phase transition from dihydrate form to anhydrous form by the solvent method. The solubility data of trehalose in water at (283.15, 293.15, 303.15, and 313.15) K was first reported in the literature by Lammert using a two step method.4 Using an isothermal technique, the solubility of dihydrate trehalose in water at (298.15, 308.15, 318.15, 328.15, 338.15, 348.15, and 358.15) K was determined by Jónsdóttir.5 Besides the basic data obtained in aqueous solution, the solubility data of dihydrate trehalose in binary water + ethanol solvent system at 310 K was determined by Bouchard.6 The data at (278.2, 288.2, and 298.2) K correlated by the modified UNIQUAC model were also reported in literature by Gong.7 However, the solubility data in a binary © 2014 American Chemical Society

water + ethanol solvent system at low water content in the above literature are insufficient to reveal the difference in solubility behavior between anhydrous and dihydrate trehalose. Moreover the correlation results of dihydrate trehalose solubility using the activity coefficient model in Gong’s work show great deviations at low water content, and the ARD value is larger than 28 %. So it is necessary not only to improve the available trehalose solubility data but also select the appropriate model to correlate the data. In our work, the solubility of trehalose in a water + ethanol solvent system was measured in detail with the mole fraction of water ranging from 0.000 to 1.000 at temperatures from (288.15 to 318.15) K using the gravimetric method. The parameters for predicting trehalose solubility at different temperatures and solvent compositions were obtained by nonlinear surface fit using the combination version of the Jouyban-Acree and van’t Hoff models which is a 3D model. Under our experimental conditions, when in equilibrium, white flocculent precipitate was observed in the slurry at water content lower than the critical point. It was obviously different from the suspension at water content higher than that point. The two kinds of crystals were collected and measured by differential scanning calorimetry (DSC) to prove the phase transition of dihydrate trehalose to anhydrous one at low water content. Received: January 13, 2014 Accepted: May 6, 2014 Published: May 15, 2014 1872

dx.doi.org/10.1021/je5000428 | J. Chem. Eng. Data 2014, 59, 1872−1876

Journal of Chemical & Engineering Data

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substituting (1 − x1) for x2. A1, B1, A2, B2, J0, J1, and J2 are 3D model parameters regressed from experimental data. The average relative deviations (ARD) were calculated using the following equation:

EXPERIMENTAL SECTION Materials. Dihydrate trehalose (mass fraction purity higher than 98.0 %) was purchased from Hayashibara Co., Ltd. (Okayama, Japan) with no further treatment. The solvent used in this experiment was ethanol (analytical reagent grade with mass fraction higher than 99.7 %) and deionized water (electrical resistivity was 18.2 MΩ·cm at 25 °C produced by Merck Millipore Mingche-D 24UV ultrapure water system). Apparatus and Procedures. The solubilities of trehalose were determined using the same apparatus and following the same procedures for the gravimetric method described in our previous work.8 Solvent mixtures with different mole fraction of water were added into the equilibrium cell. The temperature of the cell was controlled by a thermostatic water bath (Shanghai Laboratory Instrument Works Co., Ltd. 501A, China). Then excess dihydrate trehalose crystals were weighed at 0.1 mg precision and placed into the above cell and mixed by a magnetic stirrer (Xiang Gang Instrument M590-O02, China) for 2 h. This shortest equilibrium time was determined by investigating the dissolution profile of dihydrate trehalose. The slurry settled for 1 h, and then 10 mL of supernatant solution were ultracentrifuged 5 min at 6000 r·min−1 (Kaida, TG16G, China) to obtain clear liquor. About 5 mL of a clear liquor was weighed and dried at 60 °C to obtain the mole fraction of trehalose, and the molecular weight of dihydrate trehalose was used to calculate all the data. Every experimental point was determined at least three times and represented by the mean value. The relative expanded uncertainties of the measurements were estimated to be 40 % for solvent mole fraction of water ranging from 0.000 to 0.250 or from 0.750 to 1.000 and 7 % for solvent mole fraction of water ranging from 0.250 to 0.750. Calorimetric measurements were carried out with a PerkinElmer Diamond DSC, and the underlying scan rate was 10 K· min−1. Models and Calculations. The combination version of the Jouyban-Acree and van’t Hoff models used to correlate the trehalose solubility with temperatures and mole fraction of water in binary solvents was listed as follows:9,10 ln(xA ) = x1 ln(xA,1) + x 2 ln(xA,2) +

x1x 2 T

ARD =

RESULTS AND DISCUSSION The 3D and 2D drawing of complete solubility data of trehalose in a binary water + ethanol solvent system at the temperatures ranging from (288.15 to 318.15) K determined by the gravimetric method are shown in Figures 1 and 2,

Figure 1. 3D scatter plot of trehalose solubility at different solvent compositions and temperatures.

respectively. The 2D drawing of partial enlargement for solubility at water content lower than 0.400 at different temperatures is illustrated in Figure 3. From Figure 3, there was

i=0

(1)

(2)

ln(xA,2) = A 2 +

B2 T

(3)

(5)

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2

B1 T

⎛ |x cal − x exp| ⎞ A A ⎟⎟ xAexp ⎝ ⎠

∑ ⎜⎜

where N represents the number of solubility data points and superscripts cal and exp represent calculated values and experimental solubility data, respectively.

∑ Ji (x1 − x2)i

ln(xA,1) = A1 +

1 N

⎛ ⎛ B ⎞ B ⎞ ln(xA ) = x1⎜A1 + 1 ⎟ + (1 − x1)⎜A 2 + 2 ⎟ ⎝ ⎠ ⎝ T T⎠ x (1 − x1) + 1 [J0 + J1(2x1 − 1) + J2 (2x1 − 1)2 ] T (4)

where xA,1 and xA,2 are the solute solubility in pure water (1) and ethanol (2) and can be expressed by van’t Hoff model as in eqs 2 and 3 and x1 and x2 are the mole fraction of water and ethanol in solute-free basis, respectively. Equation 4 is the 3D model used to correlate solubility xA with temperature T and water mole fraction x1. It was obtained by combining the van’t Hoff model with the Jouyban-Acree model (eq 1) and

Figure 2. 2D scatter plot of trehalose solubility at different solvent compositions and temperatures. 1873



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methods.3 The reason may be that the equilibrium temperature and pressure in the literature were both higher than those of our experiments, and the solution volumes (10 μL in literature, and 50 mL in our work) varied significantly. The experimental pressure, temperature, and volume may have an influence on the critical value of solvent composition for trehalose phase transition. Initially all the data, a total of 117 data points, was correlated using the combination version of the Jouyban-Acree and van’t Hoff models, and the 3D nonlinear surface fit plot is shown in Figure 5. The correlation results show great deviations around

Figure 3. 2D scatter plot of trehalose solubility at water content less than 0.400 and different temperatures.

a minimum point at every equilibrium temperature corresponding to a critical x1 value (water content) at 0.040−0.050. The suspension formed below the critical point was flocculent, apparently different from that above the critical point. The DSC thermograms of the two kinds of crystals are shown in Figure 4.

Figure 5. 3D nonlinear surface fit plot of ln(xA) versus T and x1 for trehalose solubility in the full range.

the critical points which led to large ARD value (54.13 %). To improve the correlation results of this model for trehalose solubility, a boundary formed by the critical points were set to divide the whole solubility surface into two parts, and then fitted separately using the 3D model. Figures 6 and 7 are 3D nonlinear surface fit plots for water content lower and higher than the boundary, respectively. The experimental solubility is listed in Table 1, and the correlated parameters and the Figure 4. DSC thermograms of trehalose collected from solubility determination: (a) hydrous crystals from suspension with water content higher than the critical point and (b) anhydrous flocculent crystals from suspension with water content less than the critical point.

The features of the thermograms for anhydrate and dihydrate trehalose agreed with the literature.1 The crystals in the slurries lower and higher than the critical point were proved to be anhydrous and hydrous, respectively. From Figures 2 and 3, it can be seen that the solubility behaviors of anhydrous and hydrous trehalose are different. The trehalose solubility increased as x1 increased when x1 was higher than the critical point and decreased with x1 as it was lower than the critical point. In the full range of data, the trehalose solubility increased with temperature, yet it varied little when x1 was lower than the critical point. The critical x1 values (mole fraction) in our work were all lower than the literature reported value of 0.096 (mole fraction) which was converted from mass fraction of 4 % at 65 °C, measured by DSC with an about 10 μL high pressure crucible pan using both isothermal and nonisothermal

Figure 6. 3D nonlinear surface fit plot of ln(xA) versus T and x1 for trehalose solubility at water content lower than the critical point. 1874



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25.71 % and 11.62 %, respectively, which indicates that the 3D model fitted the data well especially for the higher water content part. When the water content was lower than the critical point, the data fluctuation was relatively high. It might due to the dehydration of suspended dihydrate trehalose that would increase the water content in binary solvent and thus may influence the solubility of trehalose.3 So the solubility at minimum points was calculated using parameters fitted from the higher water content part. Comparison between literature reported values with the calculated values of trehalose solubility by the combination version of the Jouyban-Acree and van’t Hoff models in binary water + ethanol solvent system and aqueous solution are shown in Figures 8 and 9, respectively. The prediction results show great deviations in pure ethanol at (278.2, 288.2, 298.2, and 310) K and in pure water at temperature higher than 318.15 K. Except for the above data points, satisfactory prediction results were obtained, the ARD values were 17.50 % and 26.13 % for binary solvent system (x1 = 0.100−1.000) and aqueous solution [T = (283.15 to 318.15) K] respectively.

Figure 7. 3D nonlinear surface fit plot of ln(xA) versus T and x1 for trehalose solubility at water content higher than the critical point.

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CONCLUSIONS The trehalose solubility in solvent compositions from 0.000 to 1.000 at temperatures from (288.15 to 318.15) K was determined using the gravimetric method. The results indicate

2

adjusted coefficient of determination (adj. R ) are shown in Table 2. For water content lower and higher than the boundary, the adj. R2 values were 0.8936 and 0.9952, the ARD values were

Table 1. Experimental Mole Fraction Solubility xexp A of Trehalose in Binary Water (1) + Ethanol (2) Mixtures at Solvent Mole Fractions of Water x1 Lower and Higher than the Critical Point at Different Temperatures T and Atmospheric Pressurea x1 ≥ 0.040−0.050

x1 < 0.040−0.050 x1

103xexp A

0.000 0.009 0.012 0.020 0.025 0.039

0.6525 0.6307 0.4883 0.4719 0.2753 0.1928

0.000 0.011 0.019 0.037

0.7007 0.6733 0.6146 0.0822

0.000 0.011 0.019 0.043

0.7780 0.8095 0.3507 0.0421

0.000 0.012 0.020 0.030

0.8516 0.8651 0.7761 0.2594

x1 T 0.048 0.100 0.148 0.200 0.300 0.400 0.499 T 0.050 0.100 0.148 0.201 0.300 0.400 T 0.051 0.101 0.117 0.156 0.199 0.299 0.400 T 0.040 0.048 0.100 0.161 0.200 0.299 0.399

103xexp A = 288.15 K 0.0314 0.0828 0.0755 0.1127 0.1769 0.4704 1.0717 = 293.15 K 0.0403 0.0827 0.0838 0.1209 0.2417 0.5520 = 298.15 K 0.0464 0.1218 0.1376 0.1171 0.1704 0.3130 0.7255 = 303.15 K 0.0448 0.0511 0.1568 0.1611 0.2144 0.4034 0.9364

x1 ≥ 0.040−0.050

x1 < 0.040−0.050

x1

103xexp A

x1

103xexp A

0.599 0.700 0.798 0.897 1.000

2.3879 4.8475 9.1590 17.5972 34.4214

0.000 0.010 0.021 0.031

0.9053 0.9412 0.6846 0.6914

0.499 0.598 0.699 0.800 0.898 1.000

1.3668 2.9313 6.0955 11.1557 21.1164 38.0608

0.000 0.010 0.020

0.9885 1.0020 1.0160

0.500 0.597 0.700 0.800 0.898 1.000

1.6944 3.8425 8.1224 15.0212 26.1257 43.6626

0.000 0.011 0.030

1.0805 1.0413 0.1422

0.500 0.600 0.700 0.798 0.898 1.000

2.1738 4.5427 9.9425 19.2631 32.7518 54.4558

x1

103xexp A

T = 308.15 K 0.040 0.0669 0.049 0.1099 0.099 0.1960 0.140 0.2321 0.199 0.2580 0.299 0.5096 0.399 1.1863 T = 313.15 K 0.046 0.0932 0.050 0.1232 0.098 0.1370 0.146 0.2893 0.200 0.3445 0.299 0.6602 0.400 1.5213 T = 318.15 K 0.041 0.1139 0.051 0.1403 0.098 0.2008 0.148 0.3696 0.200 0.4889 0.299 0.9273 0.399 1.9407

x1

103xexp A

0.500 0.610 0.710 0.783 0.898 1.000

2.8007 6.5068 13.2056 24.9008 42.3724 63.5541

0.500 0.600 0.701 0.800 0.897 1.000

3.6079 8.3312 17.9826 31.3391 47.7290 68.2549

0.499 0.589 0.700 0.809 0.897 1.000

4.7141 10.3401 21.8481 40.8350 82.4981 114.2871

a The standard uncertainty for temperature is u(T) = 0.05 K, the relative standard uncertainty for solvent mole fraction of water is ur(x1) = 0.005, and the relative expanded uncertainties for the solubility are Ur(xexp A ) = 0.4 when 0.000 < x1 < 0.250 or 0.750 < x1 < 1.000, and Ur(xexp A ) = 0.07 when 0.250 < x1 < 0.750.

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Table 2. Model Parameters Correlated from Experimental Trehalose Solubility Data x1 = 0.000−1.000 x1 < 0.040−0.050 x1 ≥ 0.040−0.050

A1

B1

A2

B2

J0

J1

J2

adj. R2

14.1635 −101.5874 11.5625

−5116.2787 7.3992·108 −4389.8132

−1.1677 −0.6812 4.6515

−1922.2120 −1937.3276 −4440.2009

−969.9028 −1.3108·109 366.6893

3031.3040 −7.7244·108 388.2256

−4436.4714 −2.0153·108 698.3842

0.9261 0.8936 0.9952

trehalose solubility at lower and higher water content were 25.71 % and 11.62 % respectively, which indicates that after it is divided into two separate parts the modeling results were improved.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Tel.: +86-431-85717211. Author Contributions §

These authors contributed equally.

Funding

This work was financially supported by Changchun University of Technology Foundation for Scientific Research and Development (LG06). Notes

The authors declare no competing financial interest.

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Figure 8. Comparison between literature reported values with the calculated values of trehalose solubility by the combination version of the Jouyban-Acree and van’t Hoff models in a binary water + ethanol solvent system.

REFERENCES

(1) Sussich, F.; Urbani, R.; Princivalle, F.; Cesàro, A. Polymorphic Amorphous and Crystalline Forms of Trehalose. J. Am. Chem. Soc. 1998, 120, 7893−7899. (2) Ohashi, T.; Yoshii, H.; Furuta, T. Innovative crystal transformation of dihydrate trehalose to anhydrous trehalose using ethanol. Carbohydr. Res. 2007, 342, 819−825. (3) Verhoeven, N.; Neoh, T. L.; Furuta, T.; Yamamoto, C.; Ohashi, T.; Yoshii, H. Characteristics of dehydration kinetics of dihydrate trehalose to its anhydrous form in ethanol by DSC. Food Chem. 2012, 132, 1638−1643. (4) Lammert, A. M.; Schmidt, S. J.; Day, G. A. Water activity and solubility of trehalose. Food Chem. 1998, 61, 139−144. (5) Jónsdóttir, S. Ó .; Cooke, S. A.; Macedo, E. A. Modeling and measurements of solid-liquid and vapor-liquid equilibria of polyols and carbohydrates in aqueous solution. Carbohydr. Res. 2002, 337, 1563− 1571. (6) Bouchard, A.; Hofland, G. W.; Witkamp, G.-J. Properties of Sugar, Polyol, and Polysaccharide Water-Ethanol Solutions. J. Chem. Eng. Data 2007, 52, 1838−1842. (7) Gong, X.; Wang, C.; Zhang, L.; Qu, H. Solubility of Xylose, Mannose, Maltose Monohydrate, and Trehalose Dihydrate in EthanolWater Solutions. J. Chem. Eng. Data 2012, 57, 3264−3269. (8) Wang, P.; Jiang, J.; He, L.; Li, H.; Li, J.; Liu, J.; Liu, X.; Luo, M.; Ma, Z.; Qiu, S.; Wu, H.; Zhao, Y. Solubility of Isomalt in the Water + Ethanol Solvent System at (288.15, 298.15, 308.15, and 318.15) K. J. Chem. Eng. Data 2013, 58, 364−369. (9) Eghrary, S. H.; Zarghami, R.; Martinez, F.; Jouyban, A. Solubility of 2-Butyl-3-benzofuranyl 4-(2-(Diethylamino)ethoxy)-3,5-diiodophenyl Ketone Hydrochloride (Amiodarone HCl) in Ethanol + Water and N-Methyl-2-pyrrolidone + Water Mixtures at Various Temperatures. J. Chem. Eng. Data 2012, 57, 1544−1550. (10) Sardari, F.; Jouyban, A. Solubility of 3-Ethyl-5-methyl-(4RS)-2((2-aminoethoxy)methyl)-4-(2-chlorophenyl)-1,4-dihydro-6-methyl3,5-pyridinedicarboxylate Monobenzenesulfonate (Amlodipine Besylate) in Ethanol + Water and Propane-1,2-diol + Water Mixtures at Various Temperatures. J. Chem. Eng. Data 2012, 57, 2848−2854.

Figure 9. Comparison between literature reported values with the calculated values of trehalose solubility by the combination version of the Jouyban-Acree and van’t Hoff models in aqueous solution.

that the solubility of trehalose increases with temperature, and have minimum points corresponding to critical water contents x1 = 0.040−0.050. The DSC results show that it is anhydrate trehalose below the critical water content and dihydrate trehalose above the critical water content. The solubility behavior of the two kinds of polymorphs is different, dihydrate trehalose solubility increases with water content, while anhydrate polymorph decreases with water content. The combination version of the Jouyban-Acree and van’t Hoff models was chosen to correlate the experimental data with water content lower and higher than the critical points. The 3D nonlinear surface fit results show that the ARD values for the 1876


Solubility of Trehalose in Water + Ethanol Solvent System from

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