Effects of Pre-Treatments and Air Drying Temperatures on Colour and Antioxidant Properties of Gac Fruit Powder

Gac fruit contains extraordinarily high levels of carotenoids that are well-known as strong antioxidants with an attractive yellow-orange-red colour. The aim of this study was to investigate the effects of different pre-treatments and air drying temperatures on colour characteristics, total carotenoid content (TCC) and total antioxidant activity (TAA) of resultant Gac fruit powder. Results showed that pre-soaking in solutions of ascorbic acid or bisulfite prior to air drying at low temperature of 40 degrees C was effective in preserving TCC and TAA. Loss of TCC and TAA increased as drying temperatures increased (50, 60, 70, and 80 degrees C). Moreover, the colour characteristics of Gac powder, such as chroma and hue angle, were not significantly affected by pre-treatments and air drying temperatures. The sorption isotherm curve of Gac aril powder has sigmoid shape.