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Influence of starter culture strains, pH adjustment and
incubation temperature on exopolysaccharide production and
viscosity in whey
Yusuf
Tunçtürk
Yüzüncü Yıl University, Department of Food
Engineering, 65080, Van, Turkey.
E-mail:
yusuftuncturk@yyu.edu.tr
Tel: +90432-2251026. Fax: +904322251104
Accepted 23 July, 2009 |
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There are many functional characteristics of
exopolysaccharides (EPS) produced by lactic acid bacteria in
fermented dairy products. In this study, 2 EPS-producing
strains of Lactobacillus delbrueckii ssp.
bulgaricus and 2 Streptococcus thermophilus
strains were isolated from commercial and rural yoghurts and
they were inoculated into whey and their effects on EPS
production and viscosity of whey were monitored. Two pH
applications (adjusted pH and free pH) and 3 incubation
temperature (42, 36 and 42/36ºC) were performed. pH of
samples was significantly affected by starter culture
strains, pH adjustment and incubation temperature (P <
0.01). Generally counts of L. delbrueckii ssp.
bulgaricus were found higher than of S. thermophilus
(P < 0.05). Viable cell counts were significantly higher, in
pH-adjusted samples and 42ºC samples, than their relevants
(P < 0.01). Higher concentrations of EPS were observed in
pH-adjusted media than that in pH-free media (P < 0.01).
Also 2-step (42/36ºC) and lower (36ºC) incubation
temperature caused an increase in EPS production. Viscosity
of samples greatly influenced from their EPS contents. The
highest EPS concentration (676 mg/L) and viscosity (6.37
mPa.s) was determined in the sample that inoculated with
S. thermophilus ST3 strain, incubated at 42/36ºC with
pH-adjustment.
Key words:
Lactic acid bacteria, exopolysaccharide, whey. |
