Effects of Chloride and Sulfate Salts on the Inhibition or Promotion of Sucrose Crystallization in Initially Amorphous Sucrose-Salt Blends.

The effects of salts on the stability of amorphous sucrose and its crystallization in different environments were investigated. Chloride (LiCl, NaCl, KCl, MgCl, CaCl, CuCl, FeCl, FeCl, and AlCl) and sulfate salts with the same cations (NaSO, KSO, MgSO, CuSO, Fe(II)SO, and Fe(III)SO) were studied. Samples (sucrose controls and sucrose:salt 1:0.1 molar ratios) were lyophilized, stored in controlled temperature and relative humidity (RH) conditions, and monitored for one month using X-ray diffraction. Samples were also analyzed by differential scanning calorimetry, microscopy, and moisture sorption techniques. All lyophiles were initially amorphous, but during storage the presence of a salt had a variable impact on sucrose crystallization. While all samples remained amorphous when stored at 11 and 23% RH at 25 °C, increasing the RH to 33 and 40% RH resulted in variations in crystallization onset times. The recrystallization time generally followed the order monovalent cations < sucrose < divalent cations < trivalent cations. The presence of a salt typically increased water sorption as compared to sucrose alone when stored at the same RH; however, anticrystallization effects were observed for sucrose combined with salts containing di- and trivalent cations in spite of the increased water content. The cation valency and hydration number played a major role in dictating the impact of the added salt on sucrose crystallization.