الفهرس 
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Abstract
150 random samples of fruit yoghurt of (Banana, Strawberry and Peach) in the form of (Set and Stirred) form (25 of each), that were collected from markets and dairy shops from different localities at El-Behera governorate and Alexandria.The collected samples were obtained on their containers as sold to the public or in sterile cup and were dispatched directly to the laboratory with minimum of delay in an ice box little aminimum of delay for preparation and examination.
All tests (sensory, chemical and Microbiological examination) of examined samples were carried out in Laboratory of Food Hygiene Dept. Fac. of Vet . Med. Alex. Univ.
The results can be summarized as follows:
1-Sensory criteria for evaluation of fruit yoghurts:
The sensory evaluation of dairy products is used to assess the quality of the products, scoring and helpful in pointing out the possible defects that may be found in order to improve the marketing and acceptability of the products.
A-Flavour: 80 % of examined set banana yoghurt samples with no flavour criticisms. The incidence of slight flavour defects was 20% for slight acetaldehyde. While, 72 % of the examined stirred banana yoghurt about with normal flavor and 7 % with slight acetaldehyde flavor. The normal samples about 88 % and slight acetaldehyde flavor samples constitute about 12 %. While, in stirred strawberry, the normal flavor samples constituted 72 % and the slight acetaldehyde samples reached to 24 % while, the definite acetaldehyde samples constituted about 4 % from all examined samples. While in set peach yoghurt the normal; flavor samples constituted 88 % and the slight acetaldehyde flavor samples constituted about 12 %. But in stirred peach yoghurt showed that, the normal flavor samples constituted about 80 % , slight acetaldehyde samples 16 % and those with definit acetaldehyde flavor reached to 4%.
B- Body and texture : The that, 92% of examined yoghurt samples had no body and texture criticisms . Meanwhile, the incidence of slight too thin defects were 8 % for grainy , ropy , too firm and weak defects , respectively . There were no samples of examined yoghurt with pronounced body and texture criticisms . also, 80 % of the examined stirrd banna yoghurt with normal body texture and 5 % of slight too thin texture. But in set strawberry yoghurt, the percentage of normal samples about 80 % and the slight too thin samples about 12 %. While, in stirred strawberry yoghurt the normal texture samples constituted about 68 %, slight too thin samples (16 %, definite too thin samples texture 8 % and slight too firm texture samples about 8 %.
While in set Peach yoghurt the, the normal texture samples constituted about 84 % and those with slihht too thin reached to 16 %. While, those of stirred peached yoghurt showed 76% of normal texture and those with slight too thin constituted about 16 % and those with definite too thin reached to 8 %
C-Appearance: 92% of yoghurt samples had no criticisms for appearance . The incidence of slight appearance criticisms were 8 % slight wheyedoff and about 80 % of examined stirred banana yoghurt with normal appearance and about 20 % of the examined samples with slight wheyed off ., the percentage of normal samples about 80 % and the slight wheyed off samples % reached to 12 %. But in stirred strawberry yogurt the normal appearance samples constituted about 72 %, slight wheyed off appearance samples constituted about 24 %and the samples of definite wheyed off samples about 4 %.
The appearance of set peach yoghurt showed that, the normal appearance samples constituted 80 % , slight wheyed samples 16 % and those with definite wheyed off examined samples reached to 4 %. But in stirred peach yoghurt samples the percentage of normal sample appearance reached to 79 %, while, those with slight wheyed off samples reached to 12 % and those with definite wheyed off reached to 12 %.
2-Biochemical examination:-
A-Acidity percent : The higher acidity % observed in Set peach yogurt samples with a mean of 3.57 ± 0.13 , followed by stirred banana yogurt with amean value of 3.55 ± 3.84 , followed by set strawberry yoghurt with a mean of 3.54 ±0.13 , followed by stirred peach yoghurt samples with a mean value of 3.53 ±0.03.
The acidity % of stirred strawberry yogurt the acidity % mean value reached to 3.52 ±0.03 , in Banna set yoghurt samples showed a lower acidity % value with a mean value of 3.47 ±0.13,
B-pH value:- The pH value showed a higher value in stirred strawberry yoghurt with a mean value of 3.82±0.03 , followed by a set banana yoghurt with a mean value of 3.81±0.14, stirred banana yoghurt with a mean value of 3.81±0.03, while, in stirred Peach yoghurt its mean value 3.79±0.04, but in set peach yoghurt its mean value was 3.55. The lower pH value observed in set strawberry yoghurt with aminimum value 3.54±0.07.
C-Moisture:- The higher moisture conatint observed in a stirred banana yoghurt samples with amean value of 81.84±0.41.The lower moisture % was observed in stirred peach yoghurt with a mean value of 78.46±2.95 and minimum value 78.40 and maximum value of 84 %. .
3-Bacteriological examinations:
A-Total coliform count: The higher total coliform count observed in set banana yoghurt with a mean value of 1.52 X103±0.05X103 , the lower total bacterial count observed in stirred banana yoghurt with a mean value of 1.32 X103±0.03 X103 and minimum value of 1.20 X103 and maximum value of 1.80 X103.
B-Total entrococci: The higher enterococci count observed in set banana yoghurt with a mean value of 2.13 X103±0.07X103 , while, the lower total enterococci count observed in stirred strawberry yoghurt with a mean value of 1.86X103±0.03 X103 .
4. Mycological examination:
A-Total yeast count:- The higher total yeast count observed in set banana yoghurt with a mean value of 2.06 X103±0.26 X103, but the lower yeast count observed in stirred strawberry yoghurt with a mean value of 0.72 X103±0.15 X103 .
B-Total mould count: The higher total mould count observed in set peach yoghurt with a mean value of 1.52 X103±0.19 X103, but the lower yeast count observed in stirred strawberry yoghurt with a mean value of 1.02 X103±0.18 X103 with a minimum value 0 and a maximum value 3.00 X 103.
The presence of moulds and yeasts in dairy products is objectionable, as they grow at a wide range of temperature and pH values resulting in spoilage of the product. They may reach the product from many different sources. Thus in some countries, yeast and mould counts are considered the standard test for checking factor sanitation.
- The most important yeasts isolated from yoghurt include, Candida krusi Candida albicans, C.galormondi, C.tropicalis and Rhodotorula. While, the most important moulds isolates include, Fusarium Spp.Penicillium Spp., A. terreus, A. flavus, A.niger, Alternaria Spp., Rhizopus Spp. and Mucor