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Bifidobacterium bifidum and Bifidobacterium infantis were added to mayonnaise as either free cells or encapsulated. The survival of bifidobacteria and their effect on mayonnaise quality were evaluated. The viability of free cells disappeared after 2 wk; however, encapsulated B. bifidum survived well for 12 and B. infantis for 8 wk. Mayonnaise containing encapsulated bifidobacteria had lower total bacterial counts compared to other treatments. Yeast and mold started to appear after 12 wk of storage in mayonnaise containing encapsulated bifidobacteria and after 6 wk with other treatments (control, cells free of bifidobacteria). Mayonnaise containing encapsulated bifidobacteria had higher titratable acidity and lower TBA values than other treatments. Sensory properties of mayonnaise were improved by the addition of encapsulated bifidobacteria.The egg yolks were mixed with all dry ingredients in a Kitchen Aid mixture (Oster, Model 972-26H, Milwaukee, WI) for 1 min at speed 4. Oil and vinegar were added alternately during a 10 min mix at speed 6. The mixture was then pasteurized at 70ЊC for 10 min and cooled.The prepared mayonnaise was divided into 5 portions for treatments. One portion was left without bacterial inoculation as a control. Two portions were inoculated separately with free and encapsulated cells of Bifidobacterium bifidum DI to a final cell concentrations of about 9.2 ϫ 10 6 CFU/g. The other two portions were inoculated with free and encapsulated cells of Bifidobacterium infantis 4038 to a final cell concentrations of about 8.9 ϫ 10 6 CFU/g. The resultant mayonnaise samples were transferred to sterile screw capped plastic jars under aseptic conditions and stored at 5ЊC for 16 wk.Samples from each treatment were taken at specified time intervals throughout storage for bacteriological, chemical and sensory evaluation. The experiment was done in triplicate and two determinations were conducted per replicate. Microbiological analysisBacterial enumeration. Bifidobacterium counts were enumerated on modified MRS (Ventling and Mistry, 1993) with NPNL (Neomycine sulphate, Paromomycine sulphate, Nalidixic acid and Lithium chloride) solution (Samona and Robinson, 1991) under anaerobic conditions using the BBL gas pak (BBL, Cockeysville, MD). The encapsulated cells of Bifidobacteria were released from the beads according to the procedure of by mixing mayonnaise sample with phosphate buffer (1M, pH 7.5).Total bacterial counts were enumerated on standard plate count agar (Marth, 1978) which was incubated at 30ЊC for 72h. Yeast and mold counts were enumerated on potato dextrose agar (Difco, 1984) which was incubated at 25ЊC for 96h. Physical and chemical analysis

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