Solubility Study and Thermal Stability Analysis of Calcium Propionate

Abstract

Solubilities in water and ethanol-water mixtures as well as the thermal behavior of the food additive calcium propionate were investigated to clarify deviations in published data. Material purified by recrystallization was used to exclude influence of impurities. Investigation of the dissociation process of calcium propionate in aqueous solution indicated that the particular shapes of the solubility curves cannot be attributed to changes in pH. The substance purchased turned out to be a mixture of the monohydrate and anhydrous calcium propionate. A new polymorph of the anhydrous calcium propionate was found and characterized. The results provide a better understanding of calcium propionate and support the development of improved crystallization processes. IntroductionCalcium propionate appears as a white crystalline solid or powder with odors resembling propionate acids [1, 2]. It is mainly used as preservative in a broad variety of products, especially in the manufacturing of baked goods. The antimicrobial action of calcium propionate is based on its dissociation process to produce undissociated propionate acid, which could diffuse across the cytoplasmic membrane. On the one hand it releases a proton to increase the energy consumption of the organism for removing the proton out, while on the other hand it accumulates in the cell and blocks metabolism by inhibiting enzymes [3]. Therefore, the pH value of the substance to be preserved is of great importance to the antimicrobial action [2].A typical concentration of calcium propionate used in bread production is 0.2 % based on the flour weight [4]. No flavor or lip feel is detectable when the concentration of calcium propionate in aqueous solutions ranges between 30 and 50 mM, which could be used with chlorinated water as a sanitary treatment for fresh-cut melon [5]. Calcium propionate is more widely used than propionic acid because it is easier to handle the solid salt than the corrosive liquid acid [3, 4]. The common method employed for the preparation of calcium propionate is the neutralization of propionic acid with calcium hydroxide in aqueous solution. The methods to achieve the solid products include spray drying, evaporation crystallization in aqueous solution or a solvent-free process, which could cause environment pollution and high costs or strong aggregation problems [6]. So, improving the solid-liquid separation process, which includes the design of an optimal crystallization process to produce calcium propionate with desired crystal size distribution (CSD), shape, and solid-state form as well as with low energy consumption and simplified procedures, is of crucial importance.Crystallization is a key technology used as a purification and isolation process both on a laboratory and an industrial scale in a wide variety of chemical engineering fields. The solids produced in crystallization processes based on different operation could have various physical and chemical properties such as CSD, crystal morphology, and solid-state form, which have a strong e...

Experimental Assessment and Modeling of the Solubility of Malonic Acid in Different Solvents

“…Similar to other dicarboxylic acids, the solubility of malonic acid has already been investigated in some studies , , but most of the studies focused on the use of pure solvents at the macroscale level. On the one hand, co‐solvency is an important strategy when a single solvent cannot meet the requirements of crystallization . On the other hand, detailed information on the intermolecular interactions during the solvation process remains unknown.…”