Microbiological tests
The spread plating, total bacterial count and bacteria cell morphology
examinations were conducted following the method described in Sun-Waterhouse, Zhou, et al. (2011). MRS and M17
media were used spread plating. The Streptococcus and Lactobacillus
were identified on the basis of colony type and confirmed by
microscopic examination using a Nikon Eclipse E600 microscope
(Nikon Instech Co. Ltd, Kanagawa, Japan), after being grown in
a MIR-162 Sanyo incubator at 37 C for 48 h. The number of bacterial
colonies of replicate plates was generated using equation (1):
Number of cfu=ml yoghurt ¼ 1
Plate Factor Dilution Factor
Average number of colonies
(1)
The “Plate Factor” and “Dilution Factor” refer to the amount of
sample pipetted onto the agar plate and the dilution series of the
yoghurt sample, respectively. The morphology of the colonies was
examined via gram staining (Harrigan & McCance, 1976) under
a Nikon Eclipse E600 microscope at two magnifications (60 and
100).