Effect of freezing rate on the rheological behaviour of systems based on starch and lipid phase
1995
Navarro, A.S. | Martino, M.N. | Zaritzky, N.E.
Starch gelatinized pastes with a lipid phase are important components of precooked frozen foods. These non-equilibrium systems undergo rheological modifications on freezing. The effect of freezing rate was analysed on different formulations containing wheat flour and corn and wheat starches. shortening and xanthan gum. Gelation characteristics of the pastes were also studied. The viscoelastic behaviour of the formulations was analysed by their transient shear stress curves (tau versus time) obtained with a rotational viscometer. The Bird-Leider model fitted the experimental curves satisfactorily. Viscoelasticity and relaxation time parameters from the model quantified the rheological changes. High freezing rates maintained the textural characteristics of the unfrozen samples. Low freezing rates increased the viscoelasticity of the pastes and decreased their apparent viscosity. These changes would reduce consumer acceptability of the product. Wheat proteins were responsible for the better performance of frozen wheat flour pastes. No effect of freezing rate was observed when xanthan gum was added to the pastes. Thus, the presence of the stabilizer (0.3%) reduces the negative effect of low freezing rates without losing product quality.
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