Moisture sorption behaviors, water activity-temperature relationships, and physical stability traits of spices, herbs, and seasoning blends containing crystalline and amorphous ingredients

[Display omitted] •Seasonings vary in moisture sorption behaviors and moisture content at a given aw.•Caking occurs when storage RH and temperature exceed the Tg of amorphous seasonings.•Blending amorphous spices with crystalline ingredients decreased physical stability.•The presence of multiple deliquescent ingredients increased caking tendency.•As seasoning blend complexity increased, sensitivity to moisture increased. Spices, herbs, and seasoning blends containing both crystalline and amorphous ingredients are common throughout the food industry but may exhibit unwanted clumping or caking during storage. Crystalline and amorphous ingredients are known to respond differently to increases in relative humidity (RH) and temperature. The aim of this study was to better characterize what happens to moisture sorption behaviors, water–solid interactions, and physical stability when crystalline and amorphous ingredients are co-formulated in seasoning blends. Spices, herbs, and seasoning blends, 25 in total, were studied individually and in blends of increasing complexity (binary, ternary, and quaternary) with sucrose, salt, and maltodextrin. The effects of increasing temperature and RH on moisture content, moisture sorption profiles, water activity (aw), glass transition temperature (Tg), including Gordon-Taylor modeling, physical appearance, and degree of clumping were measured. Crossover points, the temperature at which the aw of the amorphous ingredient(s) and the deliquescence RH of the crystalline ingredient(s) in a blend intersect, were also calculated. Caking was observed when storage conditions (RH and/or temperature) exceeded the Tg of a blend or the deliquescence RH of a crystalline ingredient in the blend. When amorphous and crystalline ingredients were blended, synergistic moisture sorption and increased caking was observed. When multiple crystalline ingredients were present, mutual deliquescence further increased the sensitivity of the blend to moisture. When environmental conditions exceeded the crossover temperature, degree of caking increased, and physical appearance was altered due to the induced deliquescence of the crystalline ingredient(s) by the aw of the amorphous ingredient(s). In general, as complexity of blends increased, sensitivity to moisture also increased, and physical stability of the blends decreased. The results of this study provide valuable information for increasing the physical stability of complex seasoning blends based on m