Stress relaxation and low field proton magnetic resonance studies of cheese analog

Cheese analog samples were prepared using two different sources of fat, milkfat and vegetable oil. The rheological properties of the samples, which ranged in moisture from 42.5 to 50%, were examined using compression and stress relaxation tests. The values of peak stress (sigma at 50% strain) from the compression tests and the initial stress (sigma (0)), equilibrium stress (sigma (e)), and elastic constant (g(1)) from the stress relaxation tests, were compared. All four values were higher for the samples containing milkfat as compared to the samples containing vegetable oil. For both analog formulations, moisture content was negatively correlated with values of sigma (0) (R-2 > 0.91), sigma (e) (R-2 > 0.80) and g(1) (R-2 > 0.94) at 40 mm/min crosshead speed. The CPMG-T-2 relaxation curves of the samples were determined using a low field (5.35 MHz) proton magnetic resonance sensor. The T-2 relaxation data were fit to a two-term exponential model having time constants T-2a and T-2b. In the model, the coefficients alpha and beta indicated, respectively, the contribution of T-2a and T-2b to the T-2 relaxation. The T-2a value was associated with the water in the analog cheese while the T-2b value was associated with the oil. The T-2a value was correlated (R-2 > 0.95) with the relative proportion of water in each sample. It increased as the moisture content increased. There were negative correlations between T-2a and sigma (0), sigma (e), and g(1) from the stress relaxation tests.