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at 50°C or below in order to deter the growth of
bacteria. Proper cooking will kill certain bacteria.
The growth of
E.coli
and the risk of developing
a food-borne illness from properly cooked foods
are low. However, in the case of RTE foods, since
the food will not be cooked again, there is no way
to kill bacteria that get on the food after its initial
cooking process. Therefore, it is essential that RTE
protein-containing foods be properly refrigerated
to prevent bacteria growth (NIAID, 2011).
Considering the growing importance in food
safety in RTE food and the current global issues,
the present study aim to evaluate the microbio-
logical quality of tuna sandwich stored at dif-
ferent temperatures. This study would generate
information on the importance of practicing
good hand hygiene in the preparation of RTE as
well as keeping the food at the appropriate tem-
perature in ensuring acceptable microbiologically
safe food. Information generated from this study
could become the basis for further investigation on
the issues as to the best of our knowledge, there
is no information available on the effects of hand
hygiene on bacterial contamination on sandwich in
Malaysia.
stomacher bag and shaken for 60 seconds. The
homogenized (1 ml) was sampled from the bag and
it was serially diluted to obtain 10
−1
, 10
−2
and 10
−3
dilution.The plates then were incubated at 30°Cin
inverted condition. After 72
3 h of incubation,
numbers of colonies per plate were counted using
a colony counter.
±
2.2.2
Detection and enumeration of coliform
Detection and enumeration of coliforms were per-
formed following ISO 7521:2005 (E) procedures
which employing Most Probable Number (MPN)
technique using a three tubessystem.According to
this procedure, a sufficient number of dilutions
were prepared to ensure all the tubes for final dilu-
tions will yield a negative result.The number of
tubes which shows positive result were counted.
Concentrations of coliforms were estimated using
MPN table as in Table B.5 in ISO 7218: 2007 (E)
(Appendix 1).
2.2.3
Detection and enumeration of E.coli
Detection and enumeration of
E.coli
were per-
formed following ISO 7251:2005 (E) employing
MPN technique using a three tubes system.The
presence of
E.coli
was indicated by the formation
of red colour in the solution (Figure 3.3). The
number of tubes with red colour formation were
counted as '
2
MATERIALS AND METHOD
ve result' and the concentration of
E.coli
were estimated using the MPN technique
according to ISO 7218: 2007 (E).
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2.1
Experimental design
All the ingredients required were purchased from
a local supermarket one day before preparation of
the sandwiches. Lettuce, cucumber and tomatoes
were kept refrigerated prior to use. The vegeta-
bles were thoroughly washed in running tap water
before cut into small pieces. Both cucumber and
tomatoes were cut at about 2 mm thick while let-
tuce was shredded with a clean knife and surface.
The tuna and salmon spreads were used and the
cans were opened just before the preparation.The
weight of each piece sandwich was standardized
to 25 g in room with a temperature of 24°C. The
preparation of the sandwiches for this was con-
ducted at the Food Service Complex, Faculty of
Food Science and Technology, Universiti Putra
Malaysia. Then the samples were stored at 4 and
30°C for 6 days.
dilutionwas performed for further microbiologi-
cal analyses which were TPC, fecal coliform count,
and presumptive E. coli detection and count.
2.3
Statistical analysis
Data on total plate counts were subjected to analy-
sis of variance (ANOVA) using Statistical Analysis
System Ver. 9.2. (SAS Institute, Cary, North Caro-
lina, USA). Mean differences between treatment
were compared using Duncan's Multiple Range
Test at P
0.05. For total coliforms and presump-
tive
E. coli
counts, MPN values were generated
based on MPN table using a three tubes system as
in ISO 7218: 2007 (E).
<
3
RESULTS AND DISCUSSION
3.1
Microbiological quality for tuna sandwiches
3.1.1
Total plate count
By overall TPC of samples prepared with poor
hand hygiene were higher (1.22E
07cfu/g)
than those prepared with good hand hygiene
(2.19E
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2.2
Microbiological analysis
2.2.1
Total plate count
Total plate counts were determined using ISO
4833:2003 (E) procedures. 25 g of sandwich
were added to 225 ml of 1% peptone water in a
06cfu/g) (Figure 1).Results showed that
TPC in tuna sandwich were markedly affected by
levels of hygiene practiced but it was dependent on
storage temperature. At 4°C storage temperature,
samples prepared with poor hand hygiene had a
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