Impact of High Hydrostatic Pressure on Composition and Quality of Yoghurt

Yoghurt was made of different levels of high hydrostatic pressure processing (HHP) (500, 600 and 700 MPa at 25oC for 10 min), compared with that made by using heat treatment (93oC for 20 min) as a control. The resultant yoghurts were analyzed for chemical, physicaland sensory properties. The pH during fermentation time was significantly higher for 700 MPa treated sample, compared to the other samples. The pressurized samples were lower in TS (P≤0.05) than heat treated sample (control). 500 MPa-treated sample had significant lower gel firmness, compared to other tested samples, whereas the highest value was recorded by 700 MPa. Applying 600 and 700 MPa of HHP on the used milk increased significantly the viscosity, compared to 500 MPa and the control samples. Considerable decrease on wheying-off was observed when the milks were pressurized with all of the applied levels. The application of HHP (600 and 700 MPa/ 10 min) to yoghurt milk improved colour and taste of the resultant yoghurt, whereas 500 MPa decreased the most of the tested sensory properties.