STRESS RELAXATION AND LOW FIELD PROTON MAGNETIC RESONANCE STUDIES OF CHEESE ANALOG*

Abstract

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 (s̀ at 50% strain) from the compression tests and the initial stress (s̀o), equilibrium stress (s̀e), and elastic constant (g1) 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 s̀o (R2 > 0.91), s̀o (R2 > 0.80) and g1 (R2 > 0.94) at 40 mm/min crosshead speed. The CPMG‐T2 relaxation curves of the samples were determined using a low field (5.35 MHz) proton magnetic resonance sensor. The T2 relaxation data were fit to a two‐term exponential model having time constants T2a and T2b In the model, the coefficients α and β indicated, respectively, the contribution of T2b and T2b to the T2 relaxation. The T2a value was associated with the water in the analog cheese while the T2b value was associated with the oil. The T2a value was correlated (R2 > 0.95) with the relative proportion of water in each sample. It increased as the moisture content increased. There were negative correlations between T2a and s̀o, s̀e, and g1 from the stress relaxation tests.