Abstract
The influences of aqueous and ethanolic extracts of propolis (1%) on growth
of common Gram-negative (Salmonella Parathyphi A, Campylobacter jejuni, Yersinia enterocolitica and Klebsiella pneumoniae) and -positive (Listeria
monocytogenes, Staphylococcus aureus and Enterococcus faecalis) food-borne pathogens and their biogenic amines (BAs) production were examined in tyrosine
decarboxylase broth (TDB). The highest growth inhibitory activity was observed
against Gram-negative S. Paratyphi A
in the existence of ethanolic and aqueous extracts of propolis, with 2.49 and 1.9 log
reduction, respectively. Ethanolic extracts of propolis were more effective
than that of aqueous extract on growth
inhibition of L. monocytogenes (p<0.05). Both extracts of
propolis had significant effect on reducing ammonia production by bacteria
(p<0.05). Tyramine, dopamine, agmatine and spermine were major amines formed
in TDB. Tyramine production was the lowest with S. Paratyphi A (1.94 mg/L) and highest with E. faecalis (254.93 mg/L).
The existence of ethanolic propolis extracts in TDB led to
significantly fewer tyramine production by Gram-positive S. aureus, L. monocytogenes and E. faecalis, and Gram-negative C. jejuni (p<0.05). Histamine produced
lower than 1.3 mg/L by all food-borne pathogens. Ethanolic extracts of propolis
generally led to lower histamine production by bacteria. The influence of
propolis on BAs production varied according to type of extracts, specific BAs
and bacterial strains. However, the aqueous of propolis generally showed a synergistic
effect on most of BAs mainly tyramine production by bacteria. Thus, the use of propolis ethanolic extracts appeared
to be more suitable than aqueous extract to control
tyramine production in foods.