Effects of Quince Seed Mucilage and Guar Gum on the Physicochemical and Sensory Properties of Doogh

Iranian famous drinking yoghurt type, named Doogh, is a fermented dairy beverage and constituts an important part of daily beverage consumption in Iran. Doogh is commonly produced from mixing of yoghurt, drinking water, salt, and essence of aromatic vegetables such as thyme, mint, and oregano. In the present work, the effects of Quince seed mucilage [Qm: 0-0.1% (w/w)], Guar gum [Gg: 0-0.2% (w/w)] and storage time (1-21 days) on the physicochemical (pH, acidity and viscosity) and sensory properties of Doogh were studied. The Doogh was stored at 4°C for 21 days to be evaluated. Quince seed mucilage and guar gum were added to Doogh based on a Central Composite Design (CCD). The Response Surface Method (RSM) was applied to find out the optimum conditions and interaction between different factors. Three factors including Doogh storage time and added percentages of Qm and Gg were investigated. The results showed that the optimum condition of factors was different based on response. Based on viscosity of the Doogh, the first day of Doogh production and 0.1% (w/w) of Qm and 0.2% (w/w) of Gg were the best condition.