The effect of gac fruit preparation addition on characteristics of yoghurt

Abstract

Gac fruit is a good source of betacarotene and lycopene. It has been recently utilized for developing various functional food products, especially for beverage category. However, little information has been provided for developing yoghurt from gac fruit. Addition of fruit to yoghurt usually effects on product characteristics such as growth of microorganisms, syneresis, viscosity and sensory acceptance. The objective of this study was therefore to evaluate the quality of gac fruit added yoghurt during storage. Gac fruit was prepared as fruit preparation containing gac fruit, sucrose, water, passion fruit juice, low methoxyl pectin and salt before mixing with yoghurt. Amount of gac fruit preparation added was varied at 5, 10 and 15% w/w. The products were then evaluated for sensory acceptance and color, and then for pH, syneresis, viscosity, and total plate count every 5 days during storage at 4 °C for 20 days.  It was found that addition of gac fruit preparation at 5%w/w received the highest liking score but not significantly different from addition of which at 10% w/w (p>0.05). The pH of all samples slightly dropped during storage whilst syneresis progressed and viscosity increased with increasing gac fruit preparation addition. However, the viscosity of all yoghurt samples decreased during storage. Furthermore, increasing amount of gac fruit preparation influenced on product’s color by lowing L* value, increasing a* and b* values. Total plate count of yoghurt samples added with gac fruit preparation changed slightly as compared to that of control in which more noticeable reduction was observed during storage.