The influence of selected prebiotics on the growth of lactic acid bacteria for bio-yoghurt production.
BACKGROUND
Prebiotics are a category of nutritional com-pounds grouped together, not necessarily by structural similarities, but by ability to promote the growth of spe-cific beneficial (probiotic) gut bacteria. Fructooligosaccharides (FOS) and inulin are among the most famous prebiotic compounds. In order to improve viability of probiotic bacteria during storage, fermented food should be supplemented with prebiotics.


METHODS
Yoghurts were produced from skimmed milk powder and prebiotics (FOS, inulin or resistant starch), which were added at concentrations of 1%, 2% and 3%. Yoghurts were stored in +4°C for three weeks. Every week each kind of fermented drink was examined in order to check the growth of lactic acid bacteria. Apparent viscosity and texture of bio-yoghurt were determinated during refrigerated storage.


RESULTS
The FOS and inulin addition to yoghurt caused an increase in the numbers of all bacteria in comparison to control yoghurt obtained without addition of prebiotics. The viable counts of Str. thermophilus, Lb. acidophilus and Bifidobacterium sp. when 1% of FOS was added to yoghurt were about 9 log cfu/g, 7.8 log cfu/g and 7.7 log cfu/g, respectively. In the presence of 1% of inulin, streptococci and bifidobacteria reached the growth at the level 8.8 log cfu/g and 7.5 respectively. Hardness and adhesiveness of yoghurt obtained with addition resistant starch increased systematically during 21 days of refrigerated storage.


CONCLUSIONS
The numbers of lactic acid bacteria in obtained bio-yoghurts were sufficient in 97% of samples (10(6)-10(9) cfu/g) according to FAO/WHO protocols. Generally, viability of bacteria was sufficient for 14 days and then their numbers decreased but usually not below 10(6) cfu/g. Prebiotics as FOS and inulin added to bio-yoghurt exhibited stimulatory effect on growth Lb. acidophilus and Bifidobacterium sp. Addition of prebiotics caused an increase in apparent viscosity and hardness (in case of FOS) and decrease in syneresis of obtained bio-yoghurts.
University of Life Sciences in Lublin.
Waldemar
W
Gustaw
Monika
M
Kordowska-Wiater
Justyna
J
Kozioł
D001644:Bifidobacterium / Q000254:growth & development / Q000302:isolation & purification; D015169:Colony Count, Microbial; D019587:Dietary Supplements / Q000145:classification*; D005285:Fermentation; D061353:Food Storage / Q000379:methods; D006863:Hydrogen-Ion Concentration; D007444:Inulin / Q000032:analysis / Q000378:metabolism; D007777:Lactobacillaceae / Q000254:growth & development* / Q000302:isolation & purification; D009844:Oligosaccharides / Q000032:analysis / Q000378:metabolism; D056692:Prebiotics / Q000382:microbiology*; D019936:Probiotics / Q000032:analysis*; D012212:Rheology; D013291:Streptococcus / Q000254:growth & development / Q000302:isolation & purification; D015014:Yogurt / Q000382:microbiology*
D009844:Oligosaccharides; D056692:Prebiotics; C116580:fructooligosaccharide; D007444:Inulin