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37
BACTERIOLOGICAL SAMPLING
Table 25
The Local Authority is responsible for food hygiene in all its aspects. In particular, the fitness or
otherwise of foodstuffs and the prevention of food borne illness. Bacteriology and sampling for bacteriological
examination is a necessary part of this duty, and during the year 239 samples of high risk foods were taken
and submitted to the Public Health Laboratory Service for examination. Of these. 183 were satisfactory and
56 were unsatisfactory.
Water Samples
Samples were taken from all the swimming baths in the Borough. Each sample was examined for
coliform bacilli and for faecal organisms. Forty-seven samples were taken and 45 were satisfactory.
Meat and Meat Products
Sixty-seven samples of meat and meat products were submitted to the Laboratory and were examined
for specific food poisoning organisms, the commonest of which are Salmonellae and Staphylococci. The
presence of these organisms in meat foods is of concern and adverse samples are always followed by a full
investigation by the Public Health Inspector. Where the food is cooked prior to eating, the danger of illness is
not such a threat but the risk of cross contamination with other products which are not cooked before consumption
is a considerable one.
Ice Cream
The manufacture of ice cream is controlled by the Ice Cream (Heat Treatment, etc.) Regulations
1959/63. Ice cream is subjected to a methylene blue reduction test in a similar fashion to milk. Although not
a statutory test, it is the accepted standard test. Samples graded 1 and 2 are satisfactory. Grades 3 and 4 are
unsatisfactory and indicate some deficiencies in practice, usually the unsatisfactory sterilisation of equipment
The standards of a producer are usually judged on a series of tests rather than one or two isolated results.
Milk
The Milk (Special Designation) Regulations 1963/65 lay down the statutory tests to be applied to
designated milk.
Ultra heat treated milk known as U.H.T. or Long Life milk is "heat treated" at a temperature of
270°F for not less than one second. The "colony count test" is applied to such milk and a satisfactory sample
must have a total colony count of less than 10.
Pasteurised milk must satisfy a methylene blue test and a phosphatase test. The methylene blue test is
a test of keeping quality and a blue dye (methylene blue) must not be discoloured in 30 minutes. In the phosphatase
test the presence of phosphatase (a milk enzyme) indicates that the pasteurisation process, which
has been subjected to homogenisation (a process of breaking up the fat to form an emulsion). Samples must
pass the methylene blue and phosphatase tests.