Sorbitol Crystallization: Factors Impacting Crystal Growth and Polymorphism in Confectionery Systems
Abstract
Sorbitol has widespread use as a bulk sweetener in sugar-free confections. While it has many desirable properties, its crystallization behavior is difficult to control and is not well understood in complex systems. This study aims to determine and quantify the effects of formulation (moisture content, seed crystals, and other sweeteners: mannitol, maltitol, glycerol, and higher saccharides) and processing conditions (shear, temperature, and aging time) relevant to confectionery manufacture on sorbitol crystal growth and polymorphism. Utilizing torque rheology and a novel TD-NMR method to quantify sorbitol crystal content, kinetic measurements for crystallization with and without shear were paired with structural measurements to determine crystallization behavior as a function of formulation and processing variables. Expectedly, gamma sorbitol seed crystals promoted crystallization in all systems studied. Seed crystals accelerated the onset of crystallization and promoted the formation of the most stable gamma polymorph. Shear had a similar impact; when shear was applied, the crystallization onset time was reduced, and crystallization of more stable polymorphs was promoted. Regardless of the presence of seeds or shear, crystallization temperature had a major impact on crystallization kinetics and crystal structure. As crystallization temperature decreased, crystallization rate increased due to increased supersaturation. Likewise, decreasing moisture content promoted crystallization through the same mechanism. While crystallization rate was elevated at lower temperatures, higher temperatures promoted the formation of more thermodynamically stable polymorphs. Sorbitol crystallization behavior was also modulated through the addition of polyols with similar molecular structures. When polyol impurities were added, crystallization was inhibited and less thermodynamically stable sorbitol crystals formed. Of the polyol impurities tested, mannitol was most effective at inhibiting sorbitol crystallization; the ability of mannitol to inhibit the onset of sorbitol crystallization was proportional to the amount added. When multiple polyol impurities were added to the system simultaneously, intermediate crystallization onset times and crystal melting points were observed; enhanced abilities to inhibit sorbitol crystallization were not achieved through the addition of impurity blends. This quantitative understanding of how key formulation and manufacturing parameters impacted sorbitol crystallization can be applied to the development of sorbitol-based products with desired physical properties and processing efficiencies.
- Publication:
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Ph.D. Thesis
- Pub Date:
- 2018
- Bibcode:
- 2018PhDT........15D
- Keywords:
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- Food science;Physical chemistry;Materials science