Study of caking in powdered foods using nuclear magnetic resonance spectroscopy

Twenty-three powdered foods and ingredients were subjected to 2 treatments: temperature scan from - 20 to 110 °C within 2 hours, and storage at 37 °C and 55 °C for 60 d. During temperature scans, the spin-spin relaxation time T₂ values of individual samples were determined using a nuclear magnetic resonance (NMR) technique, resulting in a temperature-T₂ curve for each sample. Four typical temperature-T₂ curve patterns were identified and were found to be closely related to the physical changes in the samples, including agglomeration, water vaporization, and caking observed during temperature scans. Based on the temperature-T₂ curve patterns, the samples were classified into 4 groups each having distinguished caking behavior. In the storage tests, the samples were removed from the incubators every half an hour during first 2 d of storage period and every day afterwards. The storage test also suggests a strong relationship between molecular mobility and caking. Monitoring changes in T₂ as a function of temperature provides information useful for predicting whether and when caking would occur.