Since At-405 rice variety showed the least
consumer acceptability for most sensory attributes,
At-405 rice incorporated yogurts did not include in
assessing bifidobacteria viability. Only the control,
and two other rice yogurt samples representing one
local rice variety (At-309) and the imported rice
variety (Thai Jasmine rice) which demonstrated an
appropriate sensory acceptability were included in
this study. B. animalis subsp. lactis BB-12 counts
in yogurts slightly increased up to 7th day of storage
and gradually decreased thereafter in the present
study (Figure 2). In At-309 rice yogurt, initial
Bifidibacterium count (8.59±0.69 log cfu.g-1) was
decreased to 8.50±0.51 log cfu.g-1 while in Thai rice
yogurt, initial Bifidibacterium count was decreased
from 8.40±0.57 log cfu.g-1 to 8.38±0.45 log cfu.g-1
at the end of storage. Highest viability loss for
bifidobacteria was observed in plain yogurt. Initial
Bifidibacterium count in rice yogurt (8.29±0.58 log
cfu.g-1) was decreased to 7.26±0.47 log cfu.g-1 at
the end of storage. Parmijit et al. (2011) suggested
that the reduction of Bifidibacterium viability during
storage might be attributed to hydrogen peroxide
produced by starter culture Lactobacilli. On the other
hand Bari et al. (2009) reported that the dissolved
oxygen content might directly affect the survival of
probiotic cultures. According to Champagne et al.
(2005) oxygen affects the probiotic cultures in two
ways. The first is direct toxicity to cells. Certain
probiotic cultures are very sensitive to oxygen and
die in its presence, presumably due to the intracellular
production of hydrogen peroxide. When oxygen is
in the medium, certain cultures, particularly, yogurt
starter culture L. delbrueckii, excrete peroxide in the
medium and thereby indirect inhibition of probiotics
such as Bifidibacterium may also occur.