Star fruit could offer inexpensive source of antioxidants

By Stephen Daniells


http://www.foodnavigator.com/news/ng.asp?n=66268&m=2niy308&c=qdrhrvoeraoqydo

Residues from star fruit, a waste product from the juicing process,
is a rich source of extractable antioxidants, says research from
Singapore.

Star fruit (Averrhoa carambola L.), also known as carambola, are
grown extensively in Southeast Asia, Australia, South America, Hawaii
and Southern Florida. Sales of star fruit from Florida were estimated
at $17.1 m in 1996.

“An increasingly growing market for nutraceuticals and functional
foods has triggered the study on natural sources of antioxidants and
their potential for nutraceuticals and functional food,” said
Guanghou Shui and Lai Peng Leong from the National University of
Singapore.

The new study, published in the journal Food Chemistry (Vol. 97, pp.
277-284), looked at methods of extraction, identification and
activity of the antioxidants found in the star fruit.

The scientists used acetone or ethanol as extraction solvents with
different ratios of water, and concluded: “The optimum conditions
used for extraction were 50 per cent acetone as extraction solvent at
90 degrees Celsius for 45 minutes,”

The average yield of polyphenols was found to be 33 milligrams per
gram of residue, which accounted for over 70 per cent of the total
polyphenol content of the whole fruit.

The Total Oxidizing Activity (TAA), measured using the ferric
reducing/antioxidant power (FRAP) assay was measured at 510
micromoles per gram, which showed that “residues from star fruit
were excellent sources of phenolics antioxidants.”

The major antioxidant present in the extract was found to be
proanythocyanidins, most notably (-)epicatechin, an antioxidant more
commonly associated with green tea and red wine.

“This suggests [star fruit has a] great commercial potential as a
nutraceutical resource or functional food ingredient. Further
research is necessary to understand its proanythocyanidin profiles
and possible dietary intake of these compounds,” concluded Shui and
Leong.

The US antioxidant market was estimated to be $370m in 2005.