The effect of starch based fat substitutes on the microstructure of set-style yogurt made from reconstituted skimmed milk powder

Seven different types of starch based fat substitutes were used for the production of set-style yogurt from reconstituted skimmed milk powder. The yogurt milks contained 14.0–15.8% total solids, 7.3–9.1% carbohydrates, 5.3–5.6% protein and 1.0–1.2% ash. The fat content of all the batches was 0.1% except the control (1.5%), which was made with anhydrous milk fat. Yogurts made with P-Fibre 150 C and 285 F contained 0.5 and 1.1% fibre respectively. Decrease in whey syneresis and increase in firmness in all the yogurts were observed during 20 days' storage at 5°C. Yogurt made with P-Fibre 150 C had the least amount of whey syneresis. Scanning electron microscopy and transmission electron microscopy revealed subtle differences in the microstructure of set-style yogurts due to the different starch based fat substitute used. 'Spikes' and 'hair' like structures were evident around the casein micelles in the milk base. They were lightly stained when compared with the caseins. Their detection in the yogurt was very difficult and only P-150 C and P-285 F substitutes were visualized whereas the others could not be detected even when their concentration was increased to 5%. Yogurt made with Lycadex® 100 was more porous and had slightly larger void spaces filled with milk serum. The use of a higher concentration (5%) of fat substitutes increased the firmness, but impaired the flavour and mouth feel of the yogurts.     

The effect of substitution of fat by microparticulate whey protein on the quality of set-type, natural yogurt

Low calorie yogurts were manufactured from reconstituted skimmed milk powder using microparticulate whey protein (Simplesse 100® in wet and dry form) as a fat substitute. They were compared with yogurt containing anhydrous milk fat (AMF 1·5%). The quality of whey protein based yogurts (at a 1·5% level of addition) was high and similar to that of the control samples containing AMF. However, serum separation was higher and firmness was lower for yogurts containing microparticulate whey protein than for those containing AMF. This difference between yogurt containing AMF and microparticulate whey protein was most marked when microparticulate whey protein (ie, wet type) was incorporated on an equivalent dry matter basis to AMF. The sensory panel identified significant differences (p<0·05) between products containing AMF and microparticulate whey protein only in terms of sour odour and perceived serum separation.