Effect of heating and freezing treatments on time independent rheological properties of cress seed gum and xanthan gum

Foods are generally subjected to thermal treatments during processing operations, which affect the rheological properties of hydrocolloid solutions. In this study, cress seed gum and xanthan gum were prepared at 1% (w/w) and subjected to heating (60ºC-30min, 80ºC-23min, 100ºC-18min and 121ºC-15min) and freezing treatments (-18ºC-24h and -30ºC-15h). Then the rheological properties of hydrocolloid solutions were determined at 25ºC by a rotational viscometer (Bohlin Model). When the hydrocolloid samples were heated, an irreversible increase in viscosity of cress seed gum solutions was observed, whereas xanthan gum would not have the ability to stand against heat treatment. In freezing process, conversion of water to ice leads to an increment in molecular association and improved rheological characteristics of cress seed gum and xanthan gum.