Effect of heat treatment on the physico-chemical properties of Mengkudu (Morinda citrifolia) extract

Extract of mengkudu was heated using a bench-top tube heat exchanger at 30, 50, 70 and 90°C for 0, 5, 10 and 15 min residence time. The treated mengkudu extract was then measured for pH, L*, a*, b* color parameters, clarity, viscosity and total polyphenol content. Results show that heating using temperature of 30 to 90°C for 5 to 15 mins significantly (p 0.05) increased the pH compared to unheated samples. However, when compared between the different heating temperature and residence time used, no significant differences were observed. Both temperature and residence time did not significantly affect total soluble solids and color parameters of L*, a*, b*. Using a higher heating temperature resulted in a reduction in clarity and viscosity but no significant effect on total polyphenol content. At higher temperature, increasing the residence time resulted in lower clarity. Residence time did not show a significant effect on total polyphenol content and viscosity.