الفهرس 
Approval SheeOnly 14 pages are availabe for public view
 |  | from | 161 |  |  |
| | | from | 161 | | |
Abstract
Milk is a widely consumed beverage that is essential to the diet of several millions of people worldwide because it provides important macro- and micronutrients. Milk is recognized as being useful during childhood and adolescence. This can lead to milk borne outbreaks caused by some VBNC bacteria as S. aureus and Salmonella.
In the present study, one hundred and sixty random samples of milk and some milk products including UHT milk, cheddar cheese, small scale ice cream and baby food (40 each). Samples were collected from El-Giza city, Egypt. The samples were examined for the presence of S. aureus and Salmonella VBNC and their way of resuscitation was studied too. Additionally, ice cream was inoculated by reference strains of the mentioned microorganisms, then stored at freezer and deep freezer and the effect of temperature on the previous microorganisms was observed.
S. aureus could be isolated from 5, 32, 15 and 8 samples of UHT milk, cheddar cheese, small scale ice cream and baby food before resuscitation with percentages of 12.5, 80, 37.5 and 20%, with mean counts of 3.3×10±2.08, 3.9×104±1.5, 5.9×104±1.2 and 4.5×10±1.33, respectively. While after resuscitation, it was isolated from 5, 38, 22 and 16 samples of UHT milk, cheddar cheese, small scale ice cream and baby food with percentages of 12.5, 40, 55 and 95%, with mean counts of 4.6×10²±3.3, 4.3×106±1.11, 1.9×105±1.23 and 3.5×102±1.65, respectively.
Moreover, Salmonella could be isolated from 0, 0, 3 and 0 samples of UHT milk, cheddar cheese, small scale ice cream and baby food before resuscitation with percentages of 0, 0, 7.5 and 0%, respectively. These numbers changed after resuscitation, to be 0, 5, 7 and 7 samples of UHT milk, cheddar cheese, small scale ice cream and baby food with percentages of 0, 12.5, 17.5 and 17.5%, respectively.
Regarding to the experimental part, the results showed that there were changes in the inoculated microorganisms count. The number of S. aureus and S. typhimurium decreased during ice cream storage as a result of low temperature that aided in entering the VBNC state, and then they retained culturability after resuscitation. Difference in count reduction between freezing and deep freezing was nearly similar, but the S. typhimurium count decreased more than that of the S. aureus.
Different findings regarding laboratory pasteurization of milk at 63˚C for 30 min, as the count of S. aureus and S. typhimurium decreased dramatically during the first few hours following pasteurization, but after 24 and 48h storage their counts started to increase and it was obviously apparent after resuscitation as the count reached 6.7, 7.3 log CFU/ml for S. aureus and 8.5, 8.7 log CFU/ml for S. typhimurium after resuscitation, respectively.
The public health significance of VBNC organisms, precautions which should be taken especially avoidance of stress factors that lead to VBNC state to control these organisms in dairy industry, as well as, the suggested sanitary measures were discussed.