Evaluation of culture media for counts of Bifidobacterium animalis subsp. lactis Bb 12in yoghurt after refrigerated storage

Abstract

The agar RCPB pH5 has been considered a good alternative for counts of Bifidobacterium in yoghurt. However, during the refrigerated storage of yoghurt it is extremely difficult to count this microorganism due to the size of the colonies, which are so small they require the aid of a stereoscope to count them. Another agar, MRS-LP, has been also recommended for counts of Bifidobacterium in the presence of yoghurt bacteria. This study evaluated the supplementation of RCPB pH5 agar with dehydrated liver extract and the salts KH2PO4, K2HPO4, FeSO47H2O, MnSO4H2O and MgSO47H2O, aiming at improving the differentiation of Bifidobacterium in yoghurt after refrigerated storage, and also evaluated the selective count of Bifidobacterium in yoghurt using the agar MRS-LP. The agar MRS-LP presented the same cell recovery as non-fortified RCPB pH5 agar, used as a standard medium, thus being considered a good option for counts of Bifidobacterium in yoghurt. The fortified RCPB pH5 also presented the same recovery as the standard RCPB pH5 medium, however, the addition of dehydrated liver extract to the RCPB pH5 agar considerably increased the size of the Bifidobacterium colonies after refrigerated storage, making differentiation of the colonies much easier and reliable when compared to the standard non-fortified RPCP pH5. The addition of the salts (KH2PO4, K2HPO4, FeSO47H2O, MnSO4H2O and MgSO47H2O) had no influence on the performance of the RCPB pH5 agar.

Comparison of Three Treatments (Two Fermented Treatments and One Nonfermented Treatment) in Production of Synbiotic Ice Cream

“…), refrigeration (Fachin et al . ), oxygen content (Homayouni et al . ), acidity, pH, the presence of other lactic acid bacteria and the addition of prebiotic compounds (Oliveira et al .…”

Physical and sensory characteristics and probiotic survival in ice cream sweetened with various polyols

“…z o.o, Warszawa, Poland) (Fachin et al . ). After 72 h of incubation, the plates containing 10–300 visible colonies were selected and counted using a colony counter (Titriplaque, LLME, Esztergom, Hungary).…”

“…Determination of the number of bacteria was made by the pour plate method. Ice cream samples (10 g) were decimally diluted in sterile peptone water (0.1%) ( (Fachin et al 2008). After 72 h of incubation, the plates containing 10-300 visible colonies were selected and counted using a colony counter (Titriplaque, LLME, Esztergom, Hungary).…”

Evaluation of different selective media for enumeration of probiotic micro-organisms in combination with yogurt starter cultures in fermented milk

“…bulgaricus, L. acidophilus, B. animalis ssp. lactis and Lactobacillus rhamnosus) were enumerated on M17,ST, MRS, MRS S, MRS C, RCA and MRS V, respectively, to evaluate the appropriate selective media for each strain (Talwalkar et al, 2003;Champagne et al, 2005;Fachin et al, 2008;Kailasapathy et al, 2008). The experiment was replicated twice.…”