الفهرس 
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Abstract
The studies aimed for the microbiological evaluation of some
foods available in the local market to determine their acceptability
for human consumption. The study included the following:-
I- Survey samples :
1. Canned foods (low acid canned foods) :
2. Frozen foods: A- Vegetables (green beans - okra)
B- Frozen meat, frozen minced meat.
11-Storage samples :
To study the effect of storage temperature and period of
storage:
1- low acldCnnned food.
2- Frozen vegetables and frozen meat.
III- Longevity samples :
To study the longevity of Staph. aureus, E. coli and
Salmonella sp. in frozen minced meat and frozen vegetables.
Survey samples :
I. Canned foods : The cans were opened and examined for
colour, appearance, ... etc. and the study of the contents of the cans
revealed the following.-
- pH decreased in some samples, but pH was normal in the
majority of samples.
and the microbiological examination of the contents of the
cans showed the following:
- Samples of the canned fish were free from the mesophilic
anaerobes and thermophilic anaerobes also the examined cans were
free from yeasts and moulds and free from H2S producing bacteria
except one sample contained H2S producing bacteria.
- The aerobic bacteria was present in low numbers and the
mesophilic aerobes were higher than thermophilic aerobes.
2. Frozen vegetables (green beans and okra) :
a- Frozen green beans:
- Total count:
Samples taken in 1994 were within the valid limits (100 000
cel1/g of sample) in the majority of samples. However, some
samples exceeded the valid limits of total count.
- In 1995 and 1996 the examination of the samples showed
the same trend i.e the majority of the sampleswere within the valid
limit, but some samples were out of limit.
The results of T.C. showed that counts varied from company
to another company and also differed from year to year for the
same company.
- Concerning yeasts and moulds counts in frozen green beans
it was found that some samples of 1994 and 1995 contained higher
yeasts and moulds counts than the valid limits (less than 50 cell/g),
but the remaining samples were within the valid limits. But
samples examined during 1996 were within the valid limits of
yeasts and moulds.
- Samples of frozen green beans were free from Salmonella
sp. and Clostridium perfringens during 1994, 1995 and 1996.
- Staph. aureus was present in frozen green beans samples
during 1994. However, Staph. counts were reduced greatly in
samples taken during 1995 and 1996.
-E. coli was present in some samples of 1994 and was less
frequent in samples of 1995 and disappeared completely in
samples of 1996.
Concerning frozen okra which was examined during 1994,
1995 and 1996, T.C. for the exam ined samples during 1994 was
within the valid limits (100000 cell/g) except some samples which
exceeded the valid limits. T.C. of samples of okra during 1995 and
1996 were within the valid limits.
- Yeasts and moulds in frozen okra increased in the samples
examined during 1994 and 1995, but their numbers decreased
greatly during 1996.
- Samples of frozen okra examined during 1994, 1995 and
1996 were free from the pathogens Salmonella and Clostridium
perfringens.
- E. coli which is an indicator of pollution was detected in
two samples during 1994 and one okra frozen sample during 1995
and disappeared completely in all investigated okra frozen samples
during 1996.
b - fiot.zcn IIlinced meat S~1I11plesr
- T.e. of the investigated minced meat samples was within
the valid limits (less than t 06/g) for all examined samples during
1994, 1995 and 1996.
- Yeasts and moulds counts were higher than the valid limits
(50 cell/g) for samples of 1994, 1995 and 1996.
- All frozen minced meat samples examined during 1994,
1995 and 1996 were free from Salmonella and ct. perfringens.
II· Storage samples :
- Canned sardine:
Canned sardine stored at 37°C yielded the following:
• No gas production in the stored cans during the storage
period (6 months) indicating the absence of gas producing
bacteria and no reactions between the food material and the
metal of the cans.
• No pronounced change In the pH of the examined sardine
cans indicating the absence of acid-producing organisms.
• T.e. of stored sardine cans were low at the beginning due to
the drastic effect of the heat treatment. However. there was a
trend of increasing T.C. by increasing the storage period.
• Yeasts and moulds disappeared completely from the
examined sardine cans.
• All investigated samples were free from I-hS producing
bacteria except one sample showed H2S production after 4
months storage.
- Canned sardine at 55°C showed the following :-
• Aerobes counts were higher than the counts of anaerobes.
• Thermophiles counts were higher than mesophiles.
• There was a slight change in pH in the majority of
investigated samples. Only one sample- in which pH
decreased greatly.
• There was coincidence between microbial counts and pH. As
total count increased pH decreased.
• Yeasts and moulds didn’t appear in samples stored at 55°C.
• Gas formation appeared at the late periods of storage (4-6
months) in cans stored at 55°C.
• H2S appeared only in one can after 4 months storage.
The storage of frozen vegetables showed the following results :-
- Total microbial counts of frozen vegetables, which were stored
frozen for 18 months, were within the valid limits (100 000 cell/g).
95
Generally, there was a trend, which showed that as storage period
increased r.c. decreased.
-Psychrophiles counts in frozen vegetables were moderate and
there was a general trend, as storage period increased Psychrophilic
organisms increased.
- Yeasts and moulds In frozen vegetables were within the valid
limits (less than 50 cell/g) and decreased as storage period
increased to disappear completely after 12 - 15 months storage.
- Coliforrns counts decreased greatly as storage period increased.
- E. coli didn’t appear in some frozen vegetables samples and
appeared in some samples where it decreased by increas ing storage
period to disappear completely after 15 - 18 months.
- Concerning pathogens, Salmonella and Clostridium perfringens
were absent in frozen vegetables, but Staph. aureus was found and
their counts decreased by increasing the freezing period to
disappear completely after 15 - 18 months.
Concerning the storage of frozen meat, results showed the
following:
- T.e. decreased as freezing period increased.
- Psychrophilic bacteria increased as freezing period increased.
- Yeasts and moulds counts decreased as freezing period increased.
- Coliform bacteria, in frozen meat, decreased as freezing period
increased.
III- Longevity of inoculated pathogens in frozen vegetables
and minced meat:
Longevity of inoculated pathogens in frozen vegetables and
frozen minced meat, stored for 3 months under freezing conditions
showed the following results:
The freezing process decreased Salmonella counts in frozen
minced meat to 50%.
Storage for 3 months freezing conditions decreased the
counts of Salmonella to disappear completely after 3 months in
frozen vegetables and to decrease greatly in frozen minced meat
after 3 months storage.
It seems that the components of minced meat protected
Salmonella to some extent from the drastic effect of freezing.
Concerning the longevity. of inoculated Staph. aureus to
frozen vegetables and frozen minced meat during freezing and
during storage at freezing conditions, results show the following:
- The freezing process caused .reduction in Staph. aureus
counts in vegetables and minced meat.
- The storage of frozen vegetables and frozen minced meat
under freezing caused continuous reduction in Staph. aureus
counts along the storage period (3 months).
- Concerning the longevity of inoculated E. coli in frozen
vegetables and frozen minced meat, it behaved as Staph. aureus,
since freezing caused reduction in E. coli counts and storage at
freezing conditions caused continuous reduction of E. coli counts.