The study aimed to investigate appropriate formula for drinking yoghurt production. The conditions were ratio of yoghurt : concentrated rambutan juice at 100 : 0 90 : 10 85: 20 and 75: 25 the effect of concentrated rambutan juice on physical and chemical and microbiological lactic acid bacteria survival appropriate proportion of syrup and lactic acid bacteria survival during storage of drinking yoghurt from rambutan juice. It was found that proportion of concentrated rambutan juice had no effect in color (L* a*) of the yoghurt (p>0.05) but its impact to b* and viscosity were significant (p≤0.05) they increased with the increased proportion of the concentrated rambutan juice. Yoghurt with 15% concentrated rambutan juice had 88% survival rate of lactic acid bacteria after stimulated digestive system. The results showed that optimal production formula of drinking yoghurt from concentrated rambutan juice and syrup were 90:10 Z(yoghurt: concentrated rambutan juice; 85:15) : syrup) Drinking yoghurt stored in the refrigerator at 4±1oC for 15 day was evaluated and found that LAB survival numbers were 9.90 log CFU/mL.

The objectives of this research were to prepare the syrup from the extracted yam bean and apply this syrup for adjusting the sweetness in the orange flavor drinking yogurt. The study made a yam bean extract concentrated by 3 difference heating methods; steaming boiling and boiled-evaporating. The results showed that a proper method was boiling yam bean extracted at a temperature of 90°C for one hour. The syrup was light brown color and not very strong smell of yam bean the total soluble solid was 20 °Brix and the non-reducing sugar content was 17.80 %. The drinking yogurt which was formulated using a ratio of set yogurt: orange juice (100%): yam bean syrup at 1:1:1 had the sensory properties (9-Point Hedonic Scale) higher than the ratio of 1:1:0.5 and 1:1:1.5 (p≤0.05). This drinking yogurt had a pH at 4.2 the total soluble solid was 15 °Brix protein was 1.75 % fat was 2.1% and non-reducing sugar content was 5.39 %. The microbiological properties passed quality standards (drinking yogurt) of Notification of the Ministry of Public Health No. 353 B.E 2556. The study of consumer acceptance on the drinking yoghurt with yam bean syrup showed that consumers had a preference for the product at like - most like level at 72 % acceptance on the product at 97 % and would buy this product at 76 %.