Effect of protein concentration on the properties and structure of concentrated yogurts

Concentrated yogurts were produced by traditional (control), direct reconst itution, ultrafiltration and reverse osmosis techniques. The membrane techn iques were applied either before or soon after incubation. The physical pro perties of the samples were monitored using a penetrometer (set yogurt) and viscometer (stirred yogurt), and the results indicated that different manu facturing techniques led to differences in the rheology of the concentrated yogurts. As expected, samples with high protein contents had greater gel s trengths. Also, the concentration techniques caused large differences betwe en the samples, even at the same protein level. The rheological properties correlated well with the microstructure as monitored by confocal laser scan ning microscopy. In general, larger compartments in the network were associ ated with a weaker structure.