Rheological and textural properties in a bakery product as a function of the proportions of the egg yolk fractions: Discussion and modelling

With the aim of widening our knowledge about the structural changes induced by the components of egg yolk granules and their relevance in baked goods, rheological and other physical parameters have been studied in a real food system and correlated with the proportion of plasma/granules added in each case. For this purpose, the whole egg yolk content was progressively substituted by its high protein-content granular fraction in a muffin recipe until a 100% granular recipe was obtained. Five different formulas, corresponding to different plasma/granules ratios, were used and another formula with 100% granules and containing mono-and diglycerides of fatty acids (E471) was tested too. Flow curves at 25 degrees C and mechanical spectra at 90 degrees C were obtained for each substitution in order to evaluate the effect of the granules on the structure of the batter. In addition, other physical parameters of the baked muffins, such as hardness, were determined. The effects of the granular fraction on the aeration of the batter and on the baked muffins were also assessed by means of image analysis. The progressive addition of granular proteins resulted in a non-linear increase in the consistency coefficient, the strength of the interactions and the hardness of the baked muffins, particularly from a plasma/granules ratio lower than 0.75. The addition of emulsifiers reverted the effects observed. These results suggest that the desirable effects of the egg yolk on the textural properties and shape of the muffin are due mainly to the effect of the plasma fraction. (C) 2015 Elsevier Ltd. All rights reserved.