Rheology and sensory profiling of set-type fermented milks made with different commercial probiotic and yoghurt starter cultures

Varieties of set-type probiotic fermented milks and yoghurt were made from recombined skimmed milk powder, anhydrous milk fat and commercial starter cultures (direct-to-vat inoculation, DVI). Serum separation of fermented milks and yoghurt with high initial rates of syneresis proceeded more slowly than separation of those with low initial rates of syneresis; the decrease during the storage period was linear and the rate of decrease was dependent on the type of starter culture used. The firmness of these products increased over the time period, and the rate of increase was linear and independent of the starter culture. The production of exopolysaccharide material by the starter microflora also influenced syneresis and firmness of the probiotic fermented milks. The average profiles of organic acids of all the products were similar with the exception of two starter cultures that generated the highest level of acetic acid. After cross-validation, classification of the starter type using the organic acids values correctly predicted the type of starter culture used for 23 out of 24 samples. All the sensory attributes were influenced by the type of starter culture used and the trial, with the exception of viscosity character; acetic acid production by the microbial species of the starter cultures had the greatest influence on the flavour attribute.