Effect of addition of gelatin on microstructure of acidic milk gels and yoghurt and on their rheological properties

A study was made of the effect of the addition of gelatin on the microstruc ture of acid-heat-induced milk gels (90 degrees C, pH = 5.3) and yoghurt wi th and without the addition of 5% of milk solids, and a comparison was made with the microstructure of acidic milk gelatin gels obtained without heati ng(pH = 5.3). It was seen that in the acid-heat-induced gels and in yoghurt the gelatin interacted with the network of milk proteins as a connection b etween the clusters formed, whereas it was the gelatin alone that was the b asis of the formation of the gel when the milk did not reach the casein coa gulation point (pH = 5.3, unheated). The results of firmness tests indicate d that the addition of 1.5% of gelatin developed fairly firm, deformable sy stems in all the cases studied, with a definite break point and almost tota l absence of syneresis. Dynamic rheology showed that the yoghurts with adde d gelatin exhibited more solid-like behaviour than the ones prepared withou t it. (C) 2000 Elsevier Science Ltd. All rights reserved.