Microstructure of Yogurt Stabilized with Milk Proteins

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Abstract
Skim milk yoghurts were stabilized with a variety of casein- and whey protein-based ingredients. Experimental yoghurts contained 1.5% added protein and were compared to a reference yoghurt prepared with 0.5% gelatin (225 Bloom strength). Scanning and transmission electron microscopy revealed extensive fusion of casein micelles in yoghurts prepared with additional casein. Yoghurts prepared with skim milk powder and milk protein concentrate were composed of casein micelle chains held together by short links. Sodium caseinate induced formation of large and extensively fused micelles. Yoghurts prepared with 3 types of commercial whey protein concentrate were similar in structure but differed distinctively from casein-based yoghurts in that casein micelles were individual in nature, with intermicellar spaces spanned with flocculated protein.