PRODUCTION AND EVALUATION OF SET YOGHURT ENHANCED WITH SOME INDIGENOUS FRUITS

Abstract

Set yoghurt was prepared using fresh milk obtained from White Fulani cow and flavoured with indigenous fruits. The fruits investigated include grapefruit, lemon, orange and pawpaw representing treatments 1,2,3, and 4 respectively while synthetic pineapple juice and plain yoghurt served as positive and negative controls representing treatments 5 and 6respectively. The yoghurts were prepared using standard procedure. Physical properties such as water holding capacity (WHC), viscosity, syneresis and pH were determined on day 1, 7 and 14 of storage on refrigerator (4℃). Chemical and proximate composition were determined using standard procedure. The antioxidant properties and microbiological status of the yoghurt were evaluated using standard procedure. All parameters were monitored on days 1, 7 and 14 of storage at 4℃. The sensory characteristics was evaluated using a five-point hedonic scale. The result obtained indicated that the storage period had significant (P<0.05) effect on the yoghurt samples. Ash and fat contents were highest at day 1 with values 1.85 and 2.45% respectively. Protein concentration (8.79%) was superior at day 7 while moisture and carbohydrate recorded the highest values (82.63 and 9.76% respectively). The orange flavoured yoghurt had the highest values of moisture (85.11%), while protein (7.90%), sodium (32.96mg/L) were observed highest in pawpaw sample. Lemon yoghurt had the highest value of 1.52% ash while the plain yoghurt recorded the highest value of 2.43% fat. Treatment and interaction effect revealed that grape at day 7 recorded the highest water holding capacity value (52.17%) and viscosity (98540mPa/s) at day 1, while orange at day 1 had the highest Syneresis value of 56.43%. Lemon flavoured yoghurt had the highest pH (5.46) at day 1, grape flavoured yoghurt in Vitamin C (11.39 mg/ml), cholesterol (34.57 mg/dl) at day 7, synthetic pineapple flavoured yoghurt in free fatty acid (5.57) at day 14 and orange flavoured yoghurt in (20.00mq/KOH) at day 7. 1,1-Diphnyl-2-picahydrazyl and Ferric reducing antioxidant’s property assay had 38.53 % and 15 mg/ml as the highest antioxidant values respectively at day 1. Day 14 had the highest value (77.11 cfu/ml) in Total Lab Count, while Total Fungi Counts and Total Lab Count had 16.11 sfu/ml and 76.22 cfu/ml respectively. Cell surface hydrophobicity shows that Lactobacillus delbueckii subsp bulgaricus was most prevalent in the yoghurt samples. Though, Plain yoghurt was the most acceptable on day 1, while synthetic pineapple flavoured yoghurt had the highest acceptability at day 7 and 14, the fruit flavoured yoghurt had better nutritional value in most parameters examined. This therefore suggest that indigenous fruits could enhance the nutritional value of yoghurt and could replace synthetic flavourants in yoghurt production.