Enumeration of bifidobacteria using Petrifilm™ AC in pure cultures and in a fermented milk manufactured with a commercial culture of Streptococcus thermophilus

• Published in: Food microbiology Vol. 28; no. 8; pp. 1509 - 1513
• Main Authors: Miranda, Rodrigo Otávio, Neto, Gabriel Gama, de Freitas, Rosangela, Fernandes de Carvalho, Antônio, Nero, Luís Augusto
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01-12-2011; Elsevier
• Subjects: Animals; Bifidobacteria; Bifidobacterium - growth & development; Bifidobacterium - metabolism; Biological and medical sciences; Cattle; Colony Count, Microbial - instrumentation; Colony Count, Microbial - methods; Counting; Culture; Culture Media - metabolism; Enumeration; Fermentation; Fermented milk; Food industries; Food microbiology; Foods; Fundamental and applied biological sciences. Psychology; Media; Microorganisms; Milk; Milk - microbiology; Milk and cheese industries. Ice creams; Petrifilm™AC; Streptococcus; Streptococcus thermophilus; Streptococcus thermophilus - growth & development; Streptococcus thermophilus - metabolism; Bifidobacteria; Petrifilm™AC; Fermented milk; Streptococcaceae; Microbiological testing; Streptococcus salivarius subsp. thermophilus; Dairy product; Bacteria; Micrococcales; Enumeration(counting); Cultured milk
• ISSN: 0740-0020; 1095-9998
• DOI: 10.1016/j.fm.2011.07.002

Bifidobacteria are probiotic microorganisms that are widely used in the food industry. With the aim of using of Petrifilm™ Aerobic Count (AC) plates associated with selective culture media, aliquots of sterile skim milk were inoculated separately with four commercial cultures of bifidobacteria. These cultures were plated by both the conventional method and Petrifilm™AC, using the culture media NNLP and ABC. The cultures were incubated under anaerobiosis at 37 °C for 24, 48 and 72 h. No significant differences (p > 0.05) were observed between the obtained counts at 48 and 72 h. Bifidobacteria counts in ABC were usually higher than in NNLP, independent of the plating method. Subsequently, fermented milk was prepared with a Streptococcus thermophilus strain, and aliquots were inoculated with the same bifidobacteria. Then, the fermented milks were submitted to microbiological analysis for bifidobacteria enumeration using the same culture media and methodologies previously described, incubated under anaerobiosis at 37 °C for 48 h. Again, bifidobacteria counts in ABC were higher than in NNLP, with significant differences for some cultures (p < 0.05). The counts obtained by both methodologies presented significant correlations (p < 0.05). The results indicate the viability of Petrifilm™AC as an alternative method for bifidobacteria enumeration when associated to specific culture media, specially the ABC.
► Evaluation of alternative methods for the monitoring of Bifidobacterium in fermented milk. ► Innovative use of a rapid method that is a valuable tool in food industry. ► Behaviour of Bifidobacterium in distinct culture media and method for monitoring.