STABILITY OF FROZEN STARCH PASTES - EFFECT OF FREEZING, STORAGE AND XANTHAN GUM ADDITION

Starch pastes act as protective systems of the solid elements in precooked frozen foods, minimizing their dehydration and chemical changes during storage. The effect of xanthan gum (0.3 % w/w) on com starch and wheat flour pastes (10 % w/w), frozen at different freezing rates and stored between -5 and -20C, was analyzed. Freezing modified the quality attributes of the starch pastes increasing exudate production, structure deterioration and rheological changes compared to the unfrozen samples. Starch pastes showed a pseudoplastic behavior and apparent viscosities decreased in frozen samples. High freezing rates led to smaller ice crystals (indirect microscopic observation) and the absence of starch retrogradation. Starch retrogradation and ice recrystallization, both contributed to the deterioration of the frozen paste during storage (spongy structure, marked decrease of apparent viscosity and increase of syneresis). The addition of xanthan gum minimized spongy structure formation, exudate production and rheological changes, however, no protective effect was observed on ice crystal sizes and on amylopectin retrogradation by Differential Scanning Calorimetry.