PHYSICOCHEMICAL EVALUATION OF SWEETENED YOGHURT ENHANCED WITH VARYING LEVELS OF SOURSOP (Annona muricata)

This study was conducted to investigate the quality attributes of sweetened yoghurt enhanced with soursop (Annona muricata). Yoghurt was produced from fresh cow milk which was clarified, pasteurized and cooled. While cooling, sweetener and soursop pulp were added, then inoculated with starter cultures and then incubated until coagulum was formed. Five treatments which include (T1-0g, T2-50g, T3-100g, T4-150g and T5-200g) of inclusion levels of soursop pulp and two storage days (day 1 and day 7). Treatment were allotted using complete randomize design in a 2×5 factorial arrangement. The proximate analysis revealed significant (p<0.05) effect on the inclusion levels. T1 was the in highest moisture (69.77%), the highest in ash (1.42%) and fat (4.03%) was T3, while T2 (9.12%) was the highest protein recorded and T5 had the highest carbohydrate (32.69%). Also, storage period showed significant (p<0.05) effect as Day 1 had the highest values in protein (5.53%) and ash (0.91%) while Day7 showed highest moisture content (66.00%). All physicochemical properties revealed significant (p<0.05) effect on inclusion levels as pH value (4.20) and syneresis (44.75%) were highest in T1 while T5 had the highest water holding capacity (41.05%) and the peroxide value was highest in T2 (5.15meqO2/kg). The storage period effect showed (p<0.05) significance values to be higher on Day7 with pH (4.28), viscosity (824.41mPa/s), syneresis (40.12%) but water holding capacity (40.05%) was higher in Day1. The antioxidant properties revealed significance at (p<0.05) on inclusion levels. T5 was the highest in both flavonoid (0.73), phenolic (3.17 mg/g) but T4 in %DPPH (49.51%). The storage period effect revealed significant difference on antioxidant properties as Day 1 had the highest total phenol (3.01 mg/g), 1, 1- diphenyl-2-picryhydrazyl (DPPH) (42.38%). This study established that the inclusion of 200g of soursop can produce value added yoghurt and best consumed after a day of production.