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℃ was effective in preserving TCC and TAA. Loss of TCC and TAA increased as drying temperatures increased (50, 60, 70, and 80℃). 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.