摘要 : This study was conducted to evaluate the sensory, rheological, chemical and microbiological properties of fermented dairy products sold in Assiut City, Egypt. 50 samples each of laban rayeb and yoghurt were randomly collected from... 展开 This study was conducted to evaluate the sensory, rheological, chemical and microbiological properties of fermented dairy products sold in Assiut City, Egypt. 50 samples each of laban rayeb and yoghurt were randomly collected from different dairy shops in Assiut City. The sensory evaluation was based on appearance (colour and free whey), texture (firmness, creaminess, viscosity, mouth feel, consistency and smoothness) and flavour (taste and aroma). The results of these 3 attributes were expressed as the overall acceptability (OAA) of the products. Syneresis was used for the rheological properties. The chemical analysis consisted of determining the percentage of titrable acidity (TA), fat, total solids (TS), solids not fat (SNF) and moisture. The microbiological examination was performed through coliform, faecal coliform, <i>Escherichia coli</i>, Enterococcaceae, <i>Staphylococcus aureus</i>, <i>Clostridium perfringens</i>, yeast and mould counting. The sensory quality of the products was slightly good, with 66 and 78% of the laban rayeb and yoghurt samples, respectively, having a relatively high score that ranged from 5-9 based on the 9-point hedonic scale. The average values of syneresis from the laban rayeb and yoghurt samples were 10.4 and 10.429 ml, respectively. The average values of TA, fat, TS, SNF and moisture in the laban rayeb samples were 1.21, 3.01, 11.30, 8.29 and 88.70%, respectively. The respective values in yoghurt samples were 1.20, 3.34, 14.02, 10.68 and 85.98%. Both the laban rayeb and yoghurt samples were highly contaminated by moulds (92 and 60% of samples, respectively), followed by yeasts (68 and 24% of samples, respectively), Enterococcaceae (30 and 28% of samples, respectively), coliforms (28 and 22% of samples, respectively), <i>S. aureus</i> (6.0 and 8.0% of samples, respectively) and faecal coliforms (4.0 and 2.0% of samples, respectively). <i>E. coli</i> and <i>C. perfringens</i> could not be detected from the samples. The examined products showed good chemical properties and composition compared to the international standards for these products. However, the microbiological quality of the examined products was lower than that required by the Egyptian and international standards. The public health significance and economic importance of the different microbial contaminants were discussed as well as the recommended hygienic measures for the production of high-quality laban rayeb and yoghurt. 收起