Elizabeth Morrow and Shelly J. Schmidt

Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign

Amorphous sugars are key ingredients in food and pharmaceutical products due to their encapsulation abilities, high dissolution rates, and high solubility. However, amorphous sugars often undergo undesirable heat and/or moisture-induced physical changes, including stickiness, caking, and recrystallization. Though the physical stability of amorphous sugars has stimulated substantial research, one aspect of physical stability requiring further study is the effect of amorphization method on moisture-induced crystallization behavior. Thus, the objectives of this research were to compare the moisture-induced crystallization behavior of amorphous sucrose prepared by various amorphization methods, including freeze-drying, spray-drying, ball-milling, melt-quenching, and spin-melt-quenching, and to assess the thermal behavior of the resultant crystals. Moisture sorption profiles of amorphous sucrose, prepared using the aforementioned amorphization methods, were obtained from 10 to 90%RH at 10%RH increments at 25°C using a Dynamic Vapor Sorption instrument. For %RH values from 10% to 40%, samples were held at the desired %RH for 2000 minutes; for %RH values from 50% to 90%, samples were held at the desired %RH until a dm/dt criterion of 0.0005% was achieved for 10 consecutive minutes. All %RH samples, as well as “as-is” amorphous samples prepared by each amorphization method, were analyzed for glass transition, cold crystallization, and melting parameters using a TA Instruments Q2000 DSC. Under the experimental conditions employed, the minimum %RH for moisture-induced crystallization at 25°C was found to differ by amorphization method. Ball-milled sucrose recrystallized at and above 30%RH; freeze-dried, spray-dried, and spin-melt-quenched sucrose recrystallized at and above 40%RH; melt-quenched sucrose recrystallized at and above 50%RH. Although freeze-dried, spray-dried, and spin-melt-quenched sucrose shared the same minimum %RH for recrystallization, notable differences in the shape of the moisture sorption profiles for each sample demonstrate that amorphization method influenced moisture sorption behavior. When recrystallized at their minimum %RH, all sample types exhibited two endothermic DSC peaks. However, the onset temperature for both peaks varied as a function of amorphization method, with ball-milled samples showing the lowest values. Overall, this research provides the food and pharmaceutical industries with new connections between commercially relevant processing methods and their impacts on stability, quality, and storage conditions of amorphous sugar-based products.