Dynamic rheology and thermal transitions in meat-based strained baby foods

Dynamic (viscoelastic) and conventional rheology (steady flow) of three commercial meat puree based strained baby foods (chicken, lamb and beef) were evaluated in the temperature range of 5-80 degrees C using a controlled rate rheometer and their thermal transitions were evaluated using a standard differential scanning calorimeter (0-100 degrees C). All samples showed a strong viscoelastic behavior with consistently higher value of storage modulus (G') as compared to loss modulus (G") in the entire frequency (omega) range studied (0.1-10 Hz). Both G' and G" values decreased with an increase in temperature at studied omega ranges between 5 and 50 degrees C. A change in the pattern was noticed for G' and G' for chicken and lamb meat was found at and above 65 degrees C while beef exhibited similar changes at 80 degrees C indicating protein denaturation related events. A power-type relationship was found satisfactory (R-2 > 0.90) to represent dynamic rheological data (storage and loss modulus-frequency). Under steady state flow, shear-thinning behavior of baby foods was generally noticed within shear rate range between 0.1 and 100 s(-1). Herschel Bulkley model represented flow data (shear stress-shear rate) adequately in the temperature range of 5-50 degrees C. The rheological relationships were not stable or satisfactory at and above 65 degrees C for both dynamic and flow rheology. Thermal transition behavior evaluated using DSC confirmed the denaturation of meat proteins in the range 65 and 80 degrees C, which was believed to be the primary reason for the unexpected rheological behavior in this temperature zone, expected contributed by individual or group of proteins. (c) 2006 Elsevier Ltd. All rights reserved.