DETERMINATION OF THE COOKING RATE OF STARCH IN INDUSTRIAL SAUCES - COMPARISON OF NUCLEAR-MAGNETIC-RESONANCE RELAXOMETRY AND RHEOLOGICAL METHODS

Flow properties and viscoelastic behaviour of starchy sauces were comp ared with relaxation parameters obtained from Nuclear Magnetic Resonan ce (NMR). The aim of this work is to study the interest of NMR relaxom etry to evaluate the cooking degree of starch in industrial sauces hea ted under various conditions. Rheological properties discriminate the cooking conditions of sauces; variance analysis shows a significant ef fect of the cooking time and the cooking temperature on the viscosity and the storage and loss modulus (G', G ''). The evolution of the NMR relaxation parameters enables to discriminate the cooking treatment; t he time and the temperature significantly influence the T1 and T2 para meters. The correlation study shows that the transversal relaxation me asurement T2 is negatively correlated to the rheological parameters. S o the parameter T2 is an indicator of the cooking rate of starch and c an consequently be an indirect, rapid and non invasive measurement of textural properties of sauces.