Hard candies produced by sucrose and doctoring agents such as glucose syrup (GS) and high fructose corn syrup (FS) have been investigated in terms of their final composition, glass transition temperature (Tg), degree of crystallinity, total soluble solids (TSS) content and water activity (aw). Additionally, time domain (TD) 1H NMR parameters of longitudinal relaxation time (T1) and second moment (M2) measurements have been used to understand the glassy state and crystallization characteristics of different hard candy formulations. Prepared candies include sucrose as the main sugar component and different levels of doctoring agents have been mixed with sucrose to obtain products with different characteristics. Results showed that addition of any doctoring agent to sucrose formulations decreased the Tg of the system significantly (p ≤ 0.05). Furthermore, GS or FS addition also induced significant changes in TSS and aw of the samples. T1 and M2 results were almost parallel to each other, both produced the highest values at the highest sucrose concentration (p ≤ 0.05). This study demonstrated that the glass transition and crystallization characteristics of hard candy formulations can be monitored and analyzed by TD NMR relaxometry, alternative to other frequently used conventional methods including differential scanning calorimetry (DSC) and X-ray diffraction.
