EFFECT OF FREEZING RATE AND XANTHAN GUM ON THE PROPERTIES OF CORN STARCH AND WHEAT-FLOUR PASTES

The effects of freezing rate on exudate production, rheological behavi our, ice crystal size, and starch retrogradation of corn starch and wh eat flour pastes (10% w/w) with and without xanthan gum (0.3% w/w) wer e studied by means of capillary suction, rotational viscometry, indire ct microscopy, and differential scanning calorimetry (DSC). Higher fre ezing rates preserved textural characteristics and produced less exuda te. In corn starch pastes, rates <1 mm h-1 caused a marked spongy stru cture, undesirable for a sauce-like product, but only a slightly spong y structure in wheat flour pastes. Xanthan gum addition maintained the smoothness characteristic of the unfrozen pastes, avoiding amylose re trogradation. However, effects on ice crystal formation and amylopecti n retrogradation were not observed. Although high freezing rates are m ostly recommended, low levels of xanthan gum maintained quality charac teristics even at low freezing rates, decreasing equipment cost.