According to our previous study (Li et al., 2011), the TPC level of
106 CFU/g in noodle samples was considered as the cut-off point
between spoiled and unspoiled. Thus, the analysis of the sample
was terminated when TPC exceeded 106 CFU/g. Firstly, the
microorganisms in control noodles increased rapidly during storage,
with TPC over 106 CFU/g immediately on the second day. After
MTLT and HTST dehydration, the samples presented a significantly
lower microbial growth rate compared with the control (Fig. 1b).
The TPC of 45 C dehydrated noodles reached 106 CFU/g after
3 days, whereas the TPC of 75 C samples exceeded 105 CFU/g after
three days and reached 106 CFU/g on the 4th day because of the
lower initial microbial content. In 120 C-treated semi-dried noodles,
a further reduced initial TPC and remarkable microbial stability
were observed, with no significant increase of TPC value
observed after one day of storage. This result may be attributed
to the damage effect of high temperature on microbial cells, thus
leading to a prolonged lag phase for microbial growth. The TPC
of 120 C samples increased to near 105 CFU/g at the 4th day and
then reached 6 lg CFU/g at the 6th day. Thus, we could conclude
that after HTST dehydration, the shelf-life of semi-dried noodles
was extended from 1 day of the control to about 5 days.