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 degrees C within 2 hours, and storage at 3 7 degrees C and 55 degrees C for 60 d. During temperature scans, the spin-s pin relaxation time T-2 values of individual samples were determined using a nuclear magnetic resonance (NMR) technique, resulting in a temperature-T- 2 curve for each sample. Four typical temperature-T-2 curve patterns were i dentified and were found to be closely related to the physical changes in t he samples, including agglomeration, water vaporization, and caking observe d during temperature scans. Based on the temperature-T-2 curve patterns, th e samples were classified into 4 groups each having distinguished caking be havior. 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 afterwa rds, The storage test also suggests a strong relationship between molecular mobility and caking. Monitoring changes in T-2 as a function of temperatur e provides information useful for predicting whether and when caking would occur.