A total of 90 random samples were taken during yoghurt manufacturing in a dairy plant in Kafr El-Sheikh governorate resembling 30 batches , 30 samples from each of raw cow milk , standardized pasteurized milk and final product . The samples were directly transferred to the laboratory under aseptic condition and subjected to the chemical and microbiological examination , in addition to the sensory evaluation of the final product .
The study revealed that , the chemical properties of the raw milk samples (fat% , protein% , S.N.F% , moisture% , PH value , acidity% and activity test ) lied within the permissible limits stated by ES , 154 – 1 ( 2005 ) . Moreover , the microbiological criteria comply this standard whereas , the samples contained relatively low counts to total bacterial ,Staphylococcus aureus , Mould , and Coliforms and free from Bacillus cereus , Listeria monocytogenes , Clostridium perfringens , Salmonella and E . coli except 3 ( 10 % ) and 9 ( 30 % ) from the samples hading total bacterial andStaphylococcus aureus counts respectively exceeded the limits .
Concerning the standardized pasteurized milk samples only minor differences could be observed in the chemical composition of the raw and standardized pasteurized milk samples, but microbiologically there is complete reduction to all microorganisms except those resist to pasteurization.
Regarding the final product the chemical properties of the samples (fat% , protein% , S.N.F% , moisture% , PH value and acidity%) consequently lied within the permissible limits stated by ES, 1000 (2005). The microbiological characteristic of the samples met the specification required by this standard except 3 ( 10 % ) samples hading mould and Coliforms counts more than 10 cfu /ml . From sensorial point of view , our study showed that all the samples examined were found in good condition and comply with the requirement of ES , 1000 ( 2005 ) except 1 ( 3.3 % ) of these samples due to hading slight wheyed off appearance defect