Abstract
Gac fruit (Momordica cochinchinensis Spreng.) is an indigenous fruit of South and Southeast
Asia. Pulp and aril of Gac fruit contain high levels of carotenoids and are known as strong
antioxidants. However, the shelf life of fresh and ripened Gac fruit is limited (about 1 week).
Gac powder is a good alternative source of raw material in food development. The aim of
this study is to investigate the nutritional value of fresh Gac fruit and the effects of different
drying processes on color characteristics, total carotenoid content, water solubility, and
water holding capacity of Gac fruit powder. Fresh Gac fruit and its powders from different
drying processes including freeze drying, spray drying and drum drying were analyzed
to determine their physical and chemical properties. The results showed that fresh Gac
fruits contained several nutrients, vitamins, minerals, and fatty acids. The moisture content
of dried Gac powder was in the range of 2-8% and was found to be suitable for long-term
storage and food development process. Spray drying (treated with pectinase) was found
to be effective in retaining the carotenoids of Gac powders (b-carotene 57 mg/100g
dried weight (DW), lycopene 139 mg/100g DW) and was similar to that of fresh Gac fruit
(60.3 and 134.2 mg/100g DW respectively). In contrast, spray drying (not treated with
pectinase) showed low amount of carotenoids (b-carotene 6.1 mg/100g DW and lycopene
12.5 mg/100g DW). Moreover, the drying processes significantly affected the color
characteristics of Gac powder, including lightness (L*), redness (a*), yellowness (b*) and
overall color difference (ΔE). Among the drying methods, the Gac fruit powder obtained
from freeze drying (with ΔE 3.9) retained most of the color similar to the fresh Gac fruit.
Gac powder obtained from spray drying (not treated with pectinase) provided the highest
water solubility value whereas freeze drying showed the lowest water solubility value. Gac
powder from freeze drying showed higher value of water holding capacity. Different drying
processes provided different effects on both carotenoid content and physical properties
of the product. In summary, spray drying process (treated with pectinase) retained more
carotenoids and exhibited good characteristics when compared to other drying processes
and can be added directly to several food products.
