A non-conventional TD-NMR approach to monitor honey crystallization and melting. (March 2021) - Berk, Berkay
Abstract: Crystallization of glucose is a natural process that could occur in honey due to several reasons and glucose is one of them. In this study, a non-conventional TD-NMR pulse sequence, Magic Sandwich Echo (MSE), was used to monitor the crystallization of honey at 14 °C. Honey samples were seeded with glucose to induce crystallization. T1 and T2 relaxation times were also measured during 96 h of storage. Mono-exponential and bi-exponential relations were used to explain T1 and T2, respectively. As a complementary method to NMR, crystal melting enthalpy was measured by differential scanning calorimetry (DSC). High correlations were detected between NMR and DSC results. T1 relaxation times did not change, whereas both components of T2 decreased with increasing time. In addition to crystallization, the melting of crystallized honey was performed at 50 °C inside the NMR system. Crystal melting was monitored in real-time, and the rate of crystal removal was fitted to a mono-exponential decay model. Highlights: Honey crystallization was monitored by DSC and different TD-NMR approaches. Magic Sandwich Echo (MSE) sequence was used for the 1st time for honey crystallization. Two proton pools with different T2 s were detected in honey during crystallization. DSC and T2 times and MSE results were found well correlated. Real time crystal melting process was successfully monitored by TD-NMR.