THE MANUFACTURE OF SET-TYPE NATURAL YOGURT CONTAINING DIFFERENT OILS .2. RHEOLOGICAL PROPERTIES AND MICROSTRUCTURE

Yoghurts rich in poly- and mono-unsaturated fatty acids were manufactu red from reconstituted skimmed milk powder using vegetable oils (olive , groundnut, sunflower ol maize) to replace the milkfat. They were com pared 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] w ere different fi om;he control yogurt containing AMF. When separation was higher and firmness was lower for all vegetable oil-containing yog hurts than for the product containing AMF. Scanning electron microscop y revealed similar microstructure, including the distribution of void spaces filled with milk serum (porosity of the protein matrices), wher eas transmission electron microscopy showed the interaction of the veg etable oil droplets with casein micelles and their participation in th e formation of the gel matrices. Copyright (C) 1996 Elsevier Science L imited