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In-Depth Information
Table 1. Most Probable Number (MPN) of total colif-
orm of tuna sandwich prepared using two levels of hand
hygiene during 6 days of storage at two temperatures.
Good hand
hygiene
(MPN/g)
Poor hand
hygiene
(MPN/g)
Storage
temperature
Days of
storage
4°C
0
0.3
×
10
1
1.1
10
1
(0.7 × 10
1
- 4.6 × 10
1
)
×
3
0.9 × 10
1
3.8 × 10
1
(0.7 × 10
1
- 4.4 × 10
1
)
(2.9 × 10
1
-
1.4 × 10
2
)
6
0.3
×
10
1
2.3
×
10
1
(2.9
10
1
- 1.1
×
(1.8
10
1
- 1.1
×
Figure 1. Changes in Total Plate Count (TPC) on tuna
sandwich prepared under two hygiene prac-tices and
stored at 4°C and 30°C.
×
10
2
)
×
10
2
)
30°C
0
0.3 × 10
1
7.5 × 10
1
(5.8 × 10
1
- 2.7 × 10
2
)
3
1.1 × 10
3
2.4 × 10
2
higher TPC value compared to TPC in samples
prepared hygienically (P
(0.9
10
3
- 5.1
×
(2.0
×
10
2
-
×
10
3
)
1.2
×
10
3
)
0.05). The overall mean
of TPC of samples prepared with good hygiene
practices was 1.39E
<
6
2.4
×
10
2
(2.0
×
10
2
>
1.1
×
10
3
- 1.2
×
10
3
)
04 cfu/g and the correspond-
ing TPC of samples prepared with poor hygiene
was 2.34E
+
04 cfu/g. However, the TPCs were
not significantly affected by storage period. In the
study, TPC has been seen to decrease when the
samples were kept at 4°C and not at 30°C, although
the condition of culture media were not at opti-
mum condition, as it it became acidic. This is well
explained by Zymslowka (1999) who pointed out
that some bacteria such as
Bacillus cereus
and
B.
subtilis
may have a higher survival rate as these two
bacteria strains were resistant to unfavorable tem-
perature and environment because they have the
ability to form spores. Similar findings were also
reported by Terzieva
et al.
(1991).
+
been used to water the crops. The vegetables could
also have been contaminated with coliform during
harvesting, transportation, and marketing or by
consumer itself prior of usage.
3.2.3
Presumptive E.coli
Presumptive
E.coli
on sandwich stored at 30°C
shows different result from those of sandwich kept
at 4°C for both hygiene levels (Table 2). At day 0
and day 3 of storage,
E.coli
was not detected but its
presence was seen at day 6 for sandwich prepared
with good hand hygiene. This result indicates that
temperature had played important role in deter-
mining the growth of
E.coli
. The high depend-
ency of bacterial proliferation on temperature is
a general phenomenon and such results have been
reported in many studies (Gibson and Roberts,
1986; McCann et al., 2003; Lopez-Velasco et al.,
2010).When the samples were stored at 30°C, the
presumptive
E.coli
in sandwich prepared with
poor hand hygiene was detected at day 0 and simi-
lar results were continuously detected until day 6
of incubation. Such response was not observed for
samples stored at 4°C. Lack of positive growth of
E.coli
at low temperature is expected and has been
frequently reported in similar studies. Velasco et
al. (2009) found that there was a slight decreased
in
E.coli
0157:H7 numbers observed after 15 days
at 4°C, while storage at 10 oC resulted in a small
increase in
E.coli
0157:H7 count. Results obtained
in this study also agreed with those reported by
Raouf et al. (2006) which indicated that the survival
3.1.2
Coliform count
The amount of coliform on all sandwiches increased
markedly from day 0 to day 3 when stored at 30°C.
The MPN of coliform was maximum at day 6 of
storage for sandwich prepared with poor hand
hygiene. However, amount of coliform decreased
from day 3 to day 6 when the sandwich prepared
with good hand hygiene was stored at 30°C.The
progressive decrease in coliform number as the
duration of storage extended is expected as col-
iform were reported to be easily inactivated or
die-off naturally (USEPA, 2006). The presence
of coliform in the sandwich may come from the
environment as they are common inhabitants of
the soil and surface water (USEPA, 2006). In this
study, coliform may be present in vegetable used
(lettuce, cucumber and tomato) as the vegetables
may collect the coliform from the soil where they
were planted and from the water source that has
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