The fermentation time (from inoculation until pH reached 4.55)
of yoghurts was significantly affected by the used strain combinations
(P < 0.0001) (Table 1). Yog-3 [CHCC-5213 (LB) þ CHCC-13140
(ST)] had the longest fermentation time (between 380 and
440 min). During fermentation, ropy texture appeared to develop
prior to gelation. The yoghurt gel was formed at pH ~4.94, but a
ropy thread (~12 cm) was detected at pH ~ 5.6 when a spoon was
dipped into the yoghurt milk and lifted up. Yog-1 [CHCC-10935
(LB) þ CHCC-13140 (ST)] sharing the same ST strain as Yog-3
showed a faster acidification (between 260 and 280 min), and the
length of the stretchable thread of the yoghurt was reduced
compared with Yog-3. Both Yog-2 [CHCC-10935 (LB) þ CHCC-3048
(ST)] and Yog-4 [CHCC-5213 (LB) þ CHCC-3048 (ST)] fermented
rapidly (200e210 min and 190e200 min, respectively) and neither
of these yoghurts showed the ability to form extendable threads. In
Yog-2, however, a smoother texture than Yog-4 could be perceived
by rubbing the yoghurt between two fingers. Thus the smoother
texture in Yog-2 could result from EPS produced by CHCC-10935
(LB), since the ST strain CHCC-3048 shared by Yog-2 and Yog-4
only produces negligible amounts of EPS (as informed by the
manufacturer).