Instrumental Texture, Syneresis, and Microstructure of Yoghurts Prepared from Ultrafiltrated Goat Milk: Effect of Degree of Concentration

The objective of this study was to determine the effect of concentration degree (1.5-fold, 2-fold, and 2.5-fold [v/v]) of ultrafiltrated goat milk on instrumental texture, syneresis, and microstructure of set-yoghurt. The milk for control yoghurt was non-concentrated. The concentration of goat milk by ultrafiltration caused an increase in the hardness, the adhesiveness, the extrusion force of yoghurt, and a reduction in the syneresis. The microstructure of yoghurts from ultrafiltrated milk showed a compact protein matrix, a small amount of void spaces, and large casein micelles in comparison to the microstructure of yoghurts from non-concentrated milk. The best texture and the smallest syneresis of goat milk yoghurts could be obtained at 1.5- or 2-fold [v/v] goat milk concentration. Yoghurt from 2.5-fold concentrated milk was characterized by a too hard and compact structure with a consistency typical for cream cheese, not yoghurt.