Compared to air-drying treatment prior to pressing, the b-carotene
and lycopene contents in the oil samples using microwave
treatment were much higher. In other words, a significant loss of
carotenoids was caused by air-drying. The main reason for this
degradation is due to heat and oxygen. Shi et al. (1999) reported
that tomato tissue was broken down by heat treatment in conventional
air-drying and was easily exposed to oxygen, which caused
the loss of lycopene. Furthermore, the lycopene content of the
microwave-dried oil sample was higher than that of the air-dried
sample in this current study and in the published data from Vuong
and King (2003). However, the highest b-carotene content of the
published oil sample was observed, followed by microwave dried
and air-dried samples. According to this study, the fresh aril was
also air-dried at 60 _C until reaching the moisture of 12–15%, then
smashed and hot steamed for 5 min prior to pressing. The difference
in carotenoids of the oil samples between the current and
published study may be due to the different varieties, growing conditions,
stage of maturity and storage conditions of the fresh Gac
fruit, and the varied drying process conditions examined. Further-