Gac aril powder processing by using microwave drying and its incorporation into the rice porridge product

Abstract

Gac (Momordica cochinchinensis Spreng) aril contains extraordinarily high contents of β-carotene and lycopene. These nutrients have proved to be beneficial to humans. Therefore, it is of interest to produce a stable and convenient Gac aril powder by using microwave drying technique that the powder can be used as a nutrient supplement and/or a natural red-orange colourant. Objective of this study was to investigate effects of pre-treatment and microwave power on the quality of Gac powder. A comparison of the quality of the microwave-dried, air-dried and freeze-dried aril powders was also made. Surface microstructures of these powders were also observed by scanning electron microscopy (SEM). The most suitable concentration of the powder incorporated into the rice porridge product was also determined. Results showed that significant effects of pre-treatments (concentration of ascorbic acid and soaking time) on the quality of the microwave-dried powder in terms of colour characteristics, β-carotene and lycopene contents were statistically found (P < 0.001). The best concentration of 0.1% (w/w) and the soaking time of 30 minutes were determined. The most suitable microwave power for drying the aril was significantly found to be 320 W. Positive effect of microwave power on microstructural changes of aril tissues were observed by using SEM. Results also indicated that the most suitable concentration of the powder incorporated into the rice porridge was 1% (w/w). Therefore, it can be concluded that the high quality of the microwave-dried powder in terms of colour characteristics, lycopene and β-carotene contents is most effectively preserved by applying the pre-treatments prior to microwave drying. It was also found that the Gac powder rich in β-carotene and lycopene contents could be incorporated satisfactorily into the porridge product.