The present study was carried out to evaluate the shelf life and sensory evaluation of yoghurt
supplemented with natamycin during refrigerator storage. Yoghurt samples were prepared and divided
into two groups; G1, control group contains Lactobacillus delbrueckii subspp bulgaricus (Lb.
bulgaricus) and Streptococcus thermophilus (yoghurt starter cultures) and G2, natamycin group contains
yoghurt starter cultures with natamycin 10 ppm. The overall sensory score of the examined yoghurt
samples G2 were higher than G1. The mean counts of Lactobacillus bulgaricus in G1 and G2 increased
gradually till 7th day of refrigeration storage reached 10.51±0.10 and 10.55±0.01 then decreased
gradually till end of shelf life reached 9.43±0.68 and 9.37±0.66. The mean counts of Streptococcus
thermophilus in both G1 and G2 were 9.55±0.68 and 9.50±0.62 at zero day then decreased gradually till
the end of shelf life reach 9.33±0.67 and 7.94±0.05. Total yeast and mold counts were detected in G1 at
7th, 14th and 21st day of refrigeration storage with mean values of 1.20±0.10, 3.20±1.09 and 3.61±0.46
log10 cfu/g; respectively. Molds and yeasts failed to be isolated from the G2 during 31 days of
refrigeration storage period. The mean values of yeast and mold counts in G2 were 1.00±0.00, 1.10±0.10
and 3.36±0.66 after 34, 37 and 40 days; respectively. The current study proved that natamycin
fortification for plain yoghurt increases its shelf-life up to 40 days with keeping its sensorial characters. |
