الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 136 |  |  |
| | | from | 136 | | |
Abstract
These tests consisted of counting, isolation, and identification of the yeasts. The highest value of yeast count in Ras cheese samples was 1095 cfu/g in Fa1 sample which taken from Dakahlia Governorate in fresh samples. The lowest value was 60 cfu/g in Fa2 sample which taken from Kafr El-Sheikh Governorate in Dayer samples. Twenty-five yeast isolates were collecting from the yeasts which grown on Rose Bengal yeast extract sucrose agar medium. The shape of yeast colonies were varied between oval and irregular of colonies, and the appearance of them were glossy and slime. Colonies dimensions were varied between 0.5 and 18 mm. Nine yeasts were identified based on morphological, biochemical, and physiological characteristics in Al-Azhar university represented in the regional center for mycology & Biotechnology and the results were Candida parapilosis, C. lusitanae, Pichia anamola, Hansenula anomala, C. pelliculosa, C. lusitanae, C. famata, C. lipolytica and Debaryomyces hansenii. Enzymes which hydrolysis proteins, lipids, and sugars by yeast during the period of ripening were studied. All yeast species were tested for proteolysis and lipolysis on PDA medium. All yeast strains gave a positive result in sugars hydrolysis and produced acids. Most yeast strains did not give gas in the Durham’s fermentation tube. Finally, the ability of yeast isolates to produce organic acids were tested. All yeast isolates gave fast results and a high concentration for producing lactic and formic acid. It was in a lower concentration in the case of citric, oxalic, and tartaric acid, but acetic acid production was small and at lowest rate.