الفهرس 
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Abstract
Part I
(Survey part)
Quality assessment of marketable yoghurt
This investigation was applied to evaluate the quality of yoghurt sold in Assiut city, Egypt, in which a total of 150 randomly collected samples of Baladi, pasteurized plain and pasteurized flavored (50 each). The sensory evaluation was based on visual, texture and flavor; and their resultant was expressed as overall acceptability (OAA). Syneresis was applied for rheological properties and pH for physical properties. Chemical analysis was applied through moisture content, TS%, fat% and SNF%. Also, titratable acidity% and starch were detected. The microbiological examination was applied for coliforms, fecal coliforms, E. coli, anaerobes and yeasts & molds.
The achieved results showed that the sensory evaluation of the pasteurized plain and pasteurized flavored samples was of higher scores than the Baladi samples, however on contrast, the syneresis was higher in the Baladi samples; in which the average values of syneresis in the the Baladi, pasteurized plain and pasteurized flavored samples were 9.98, 5.54 and 6 ml, respectively. The average values of pH were 4.85, 4.89 and 4.81, respectively. The average values of titratable acidity% were 0.95, 0.86 and 0.79, respectively; furthermore, the average values of fat% were 2.45, 2.92 and 0.81%, respectively; while, the average values of SNF% were 9.38, 10.39 and 18.83%, respectively; and for the TS%, the average values were 11.83, 13.31 and 19.64%, respectively. The average moisture% values were 88.18, 86.69 and 80.36%, respectively. All the examined Baladi samples were starch free, while 72 and 70% of the pasteurized plain and pasteurized flavored types contained starch, respectively.
The microbiological examination cleared that the Baladi samples were more contaminated for coliforms, fecal coliforms and E. coli. The incidence of coliforms was 30, 6 and 8% in the Baladi, pasteurized plain and pasteurized flavored samples, respectively. The same incidences were achieved for fecal coliforms in the 3 yoghurt types. For E. coli, the incidences were 22, 2 and 2%, respectively. The pasteurized plain (24%) and the pasteurized flavored (16%) samples were more contaminated for anaerobes than the Baladi samples (6%). The incidences of yeasts & molds were 92, 92 and 98%, for the Baladi, pasteurized plain and pasteurized flavored samples, respectively.
Part II
(Experimental part)
Improvement of yoghurt quality by addition of omega-3 rich oils
In this part of the current study, omega-3 rich chia seeds and flaxseeds were added to the yoghurt in different forms. The supplemented chia seeds were used in the forms of seeds, grounded seeds powder (GSP) and chia seed water extract (CSWE) at 0.5, 1, 1.5, 2, 3% of the prepared milk for yoghurt manufacture. The forms of addition of flaxseed were seeds and grounded seeds powder (GSP) at 0.5, 1, 1.5, 2, 3% of the prepared milk for yoghurt manufacture. The flaxseed oil was used in a concentration of 0.32% of the milk used for yoghurt manufacture. The manufactured yoghurts were quality monitored through examination of sensory, rheological, physical, chemical and microbiological examinations.
The control yoghurt (that prepared during chia seeds supplementation) showed the values of 8.38% for OAA, 11.5 ml for syneresis, 5.1 for pH, 0.792% for acidity, 93% for moisture, 7% for TS%, 1.7% for fat, 5.3% for SNF, and was starch free; and for the coliforms, fecal coliforms and E. coli were <3, yeasts & molds were 1.23×105 and anaerobes were negative. The yoghurt supplemented with chia seeds 2 and 3% and GSP 1, 1.5, 2 and 3% showed high significant increase in total solids.
The control yoghurt (that prepared during flaxseed supplementation) showed the values of 8.13% for OAA, 9.5 ml for syneresis, 4.8 for pH, 1.35% for acidity, 90.05% for moisture, 9.95% for TS%, 1.9% for fat, 8.05% for SNF, and was starch free; and for the coliforms, fecal coliforms and E. coli were <3, yeasts & molds were 2×104 and anaerobes were negative. The yoghurt supplemented with flaxseed 2 and 3% and GSP 1.5 and 3% showed high significant decrease in syneresis.