Yoghurt made from lactose hydrolysed or unhydrolysed milks in presence of
yoghurt bacteria (Lactobacillus delbrueckii ssp. bulgaricus LX and Streptococcus
thermophilus S3) and four strains of bifidobacteria (B. bifidum DSM 20456, B. bifidum
DSM BB12, B. longum DSM 20097 and B. infantis DSM 20090) were assessed
during 15 days of refrigerated. A reduction in milk lactose of 42.3% was achieved
using Maxilact, 20000. Milk was inoculated at a level of 2% (v/v) with a bacterial
mixture of Bifidobacterium spp. :Str. thermophilus :L. delbrueckii ssp. bulgaricus using
a ratio of 2:1:1 (v/v/v). During storage, hydrolysed yoghurt showed higher titratable
acidity and lower pH values than unhydrolysed yoghurt. Hydrolysed yoghurt showed
higher acetaldehyde and soluble tyrosine contents but lower lactose content and (3-
galactosidase activity than unhydrolysed yoghurt. Sensory assessment data showed
that hydrolysed yoghurt containing B. longum or B. bifidum gained the highest flavour,
texture and overall scores. While, standard yoghurt and yoghurt containing B. infantis
scored lower because of the appearance of bitter off-flavour in the former and
unpleasant flavour in the latter samples. In conclusion, B. longum proved to be a
promising candidate to be used as dietary adjunct in fermented milk with probiotic
properties.