Extruded Maize Flour as Texturizing Agent in Acid-Unheated Skim Milk Gels

Abstract

Starches have been used to improve the textural properties, substitute fats or increase satiety in yoghurts and acidified milk gels, however studies involving addition of flours are scarce. The objective of this study was to analyze the effect of skim milk substitution by pregelatinized extruded maize flour on the acidification process (changes in pH and rheology), textural properties, syneresis and microstructure of acidified milk gels (15% w/w solids). To this end, pregelatinized flour was used to replace 17, 33 and 50% of the skim milk powder. A greater proportion of flour resulted in a faster acidification process and a higher pH at the gelation point, indicating a faster gelation. The substitution of milk by flour up to 33% increased the firmness and consistency of the set gel, but these changes were reversed with greater substitution levels due to the lack of a connected protein structure. In addition, a greater syneresis of the gels was observed as the milk content was reduced, an effect that was reversed by increasing the percentage of solids in the mixture.