A method is described for determining the solubility of multicomponent crystalline compounds from clear points upon sample dilution at a constant temperature. Clear points are established by continuously adding a solvent mixture to a suspension of known composition until a clear solution appears. For validation, this solvent addition method is compared to the traditional equilibrium concentration method at constant temperature and the more recent temperature variation method with which clear point temperatures are determined upon increasing the sample temperature. Solubility data of binary systems (1 solute, 1 solvent) measured using the solvent addition method are obtained relatively quickly compared to the equilibrium concentration method. These solubility data are consistent with those of the temperature variation and the equilibrium concentration method. For the temperature variation method, the results are dependent on the heating rate. Likewise, for the solvent addition method, they are dependent on the addition rate. Additionally, for ternary systems involving antisolvent or cocrystals, solubilities are determined at a constant temperature using the solvent addition method. The use of the solvent addition method is especially valuable in the case of solvent mixtures and other complex multicomponent systems, in which the temperature variation method cannot be applied easily. ■ INTRODUCTIONIn production often a crystallization step is required for purification and final crystalline particulate product formation. 1,2 The solubility or phase diagram of such compounds is essential information for efficient and reliable crystallization process design and operation. 3−6 The phase diagram indicates the most stable phases at specific compositional and temperature conditions, 1,4−6 determines the achievable yield, 7 and enables the monitoring of the supersaturation during the crystallization process. 7,8 Traditionally the solubility is measured through equilibration of a suspension. 1 The solubility is then equal to the concentration in the equilibrated solution, which can be sampled and determined by, for example, a gravimetric method or HPLC (Figure 1 (left)). Although the Equilibrium Concentration (EqC) method is widely accepted and considered accurate, 1 it is laborious and time-consuming. Currently, commercial equipment from various suppliers is available that streamlines measurements through a temperature variation (TV) method in which clear points are measured. 9−11 In the TV method the solubility is changed by changing the temperature, until it matches the concentration. A clear point is then the temperature at which, upon increasing the temperature, a suspension turns into a clear solution. Figure 1 (center) shows the principle of a clear point measurement using the TV method. If the heating rate is sufficiently small, the crystal dissolution rate is fast and the clear point can be assumed to be equal to the saturation temperature. 10 This TV method is much less labor intensive, is much faster, and allows f...

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This version is available at https://strathprints.strath.ac.uk/59904/ Strathprints is designed to allow users to access the research output of the University of Strathclyde. Unless otherwise explicitly stated on the manuscript, Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Please check the manuscript for details of any other licences that may have been applied. You may not engage in further distribution of the material for any profitmaking activities or any commercial gain. You may freely distribute both the url (https://strathprints.strath.ac.uk/) and the content of this paper for research or private study, educational, or not-for-profit purposes without prior permission or charge. The aim of this paper is to produce spherical encapsulates of wheat gluten in a food-15 grade biopolymer for preparing sheared meat analogs, in order to prevent instant 16 fibrilization of the gluten during a pre-mixing step. The hydrogel should release the 17 gluten inside the Couette Cell, as a result of the higher temperature and shear in the 18 process. Both sodium alginate and -carrageenan were used as encapsulants. 19Spherical particles of hydrogel-gluten mixtures were produced by means of a 20 dripping method using an encapsulator. While the particle properties of -21 carrageenan surpassed those of alginate in terms of controlled release of the core, the 22 particle production using the encapsulator was more complicated. carrageenan, a layer of oil on top of the cross-linking bath fluid, as well as through 24 the outer orifice of a concentric nozzle were required to obtain a good sphericity of 25 2 the particles. For the alginate particles the use of oil was not necessary. Gluten 26 loadings of 7 % w/w were achieved with 1.5 % w/w alginate and with 2 % w/w 27 -carrageenan. The water content of the particles can be easily controlled by a 28 subsequent partial drying step. A mixture of Soy Protein Isolate (SPI) and particles 29 was sheared in the Couette Cell. Controlled release of the gluten from the alginate 30 particles was not achieved properly by temperature or shear. The controlled release 31 of the gluten was achieved at the processing conditions only with -carrageenan. 32Some fibrilization was observed in the sheared product, but the macrostructure was 33 not yet well developed. However, an optimization of the shearing process for the use 34 of the particles may lead to an improved structure for the meat analogs. 35 36 Practical applications 37This paper investigated the effect of encapsulation in hydrogels on the fibrilization 38 behavior of wheat gluten upon contact with water. A cheap and easily scalable 39 dripping technique was used to create spherical particles in which the gluten did not 40 fibrilize, although the coating material consists of ≥95% of water. Upon reaching the 41 process conditions in the shearing device, the gluten are released and able to form 42 fibers. The results show that hydrogels can mechanically protect the c...