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Growth and viability of
yogurt starter organisms in honey-sweetened skimmed milk
Ali Riazi*
and Hasnia Ziar
Department of Biotechnology, University of Abdelhamid Ibn
Badis, Lahcen Street, PO Box 300, Mostaganem 27000, Algeria.
Affiliations: Food Safety and Health Laboratory, Department
of Biotechnology, University of Abdelhamid Ibn Badis,
Mostaganem 27000, Algeria.
*Corresponding author. E-Mail:
ardz22003@yahoo.fr.
Tel: (+213) 6 61 69 45 21. Fax: +21345 26 54 52.
Accepted
12 May, 2008 |
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Lactic acid bacteria (LAB): Streptococcus thermophilus
TA 040 and Lactobacillus delbrueckii spp.
bulgaricus Lb 340, were cultured in reconstituted (10%,
w/v) skimmed milk with 5 or 10% (w/v) polyfloral or
unifloral honey. Inoculated samples were incubated
aerobically at 42°C until milk coagulation. Samples were
collected at 2 h intervals and examined for biomass and pH
changes. Cell viability and post-acidifying activity of both
strains during 28 days of storage at 4°C were also measured.
A
higher increase
(P<0.05)
in
growth and acidifying activity of
S. thermophilus
monocultures was observed when 10% honey was added.
However, L. bulgaricus did not show such a marked
increase in its growth capacity. In associated cultures, LAB
growth was slightly inhibited, whereas curdling time was
prolonged by an hour when 10% honey was added and yogurt
acidity was moderate.
Cell viability improved by 5 to 6.6% for
S. thermophilus
and 10% for
L.
bulgaricus
in pure
honey-sweetened cultures over 28 days of refrigerated
storage.
This protective effect of honey on LAB cell viability was
also observed in associated cultures (10 to 12%
comparatively to the control).
Key
words:
Streptococcus thermophilus, Lactobacillus
bulgaricus, honey, growth, viability. |
