The manufacture of set-type natural yoghurt containing different oils .2. Rheological properties and microstructure

Yoghurts rich in poly- and mono-unsaturated fatty acids were manufactured from reconstituted skimmed milk powder using vegetable oils (olive, groundnut, sunflower ol maize) to replace the milkfat. They were compared with a yoghurt-containing anhydrous milk fat [AMF, 1.5% (w/w)]. The vegetable oil-based yoghurts [at a 1.5% (w/w) level of addition] were different fi om;he control yogurt containing AMF. When separation was higher and firmness was lower for all vegetable oil-containing yoghurts than for the product containing AMF. Scanning electron microscopy revealed similar microstructure, including the distribution of void spaces filled with milk serum (porosity of the protein matrices), whereas transmission electron microscopy showed the interaction of the vegetable oil droplets with casein micelles and their participation in the formation of the gel matrices. Copyright (C) 1996 Elsevier Science Limited