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Abstract
Because of the public health importance of biogenic amines in
dairy products, the work was planned to study: (1): the levels of most
common amines such as histamine, tyramine, tryptamine, cadaverine and
putrescine in Ras and Mish cheese. (2): isolation of some microorganisms
responsible for biogenic amines production. (3): effect of storage
temperature and ripening period on the levels of biogenic amines.
The obtained results reveal that histamine, tyramine, tryptamine,
cadaverine and putrescine were detected in 100 % of examined Ras
cheese. The average levels were 8.28, 1.20,7.74,4.42 and 3.72 mg / 100
g, respectively. Concerning Mish cheese, they were detected in 100 % of
examined samples, with average levels of 6.56, 0.86, 9.36, 3.32 and 4.05
mg / 100 g, respectively. The obtained levels were existed within the
permissible limits of different organizations including Egyptian
Standards.
The illustrated results reveal that Enterobacteriaceae, enterococci
and lactobacilli were detected in 40 %, 100 % and 100 % of Ras cheese
samples, respectively. The average counts were 2.3xl02, 6.2xl05 and
8.9x107 cfu / g, respectively. The results also showed that Enterococcus
faecalis was found in 100 % of the examined samples. The isolates of
Enterobacteriaceae were identified as E.coli (32.50 %), Proteus vulgaris
(12.50 %), Enterobacter aerogenes (15.0 %), Klebsiella pneumoniae
(22.50 %), Citobacter divers us (12.50 %) and Citrobacter amalonaticus
(20.0 %). On the other hand, the examined samples of Mish cheese had
no detectable counts of Enterobacteriaceae, enterococci and lactobacilli.
There was highly significant positive correlation coefficient was
detected between histamine content and counts of Enterobacteriaceae,
while significant positive correlation coefficient was existed between
histamine and counts of lactobacilli. Moreover, highly significant positive
correlation coefficient was found between tyramine and the counts of
enterococci and lactobacilli.
The results of experimental study in Ras cheese clearly point out that the
higher storage temperature and long ripening period increase the levels of
biogenic amines. Histamine levels reached toxic dose by the day 105 and
75 of storage at 18-22 °C and 32°C, respectively. While tyramine
reached toxic dose by the day 105 of storage at 32°C.