Milk-gel structure. IV. Microstructure of yoghurts in relation to the presence of thickening agents

Abstract

Summary The effects of 3 different thickening agents on the microstructure of yoghurt were examined by scanning and transmission electron microscopy. Unsupplemented yoghurt consisted of casein micelles fused together and linked in long chains; they seldom appeared in clusters. The addition of 0·5% gelatin caused no observable change in the yoghurt structure. Carrageenan (0·4%) formed a markedly fibrillar microstructure which connected large clusters of casein micelles. The fibres were thin and long and no free terminations were observed. Pregelatinized waxy maize starch (2%) appeared under scanning electron microscopy in the form of short fibres and sheets. The fibres frequently had free terminations and only some of them were connected with small clusters of casein micelles. Transmission-electron microscopy did not distinguish between pregelatinized starch and carrageenan additives.