The production of clear apple juice involves addition of an enzyme to remove the pectin and starch content of the cloudy juice. Writing in the Journal of the Science of Food and Agriculture, the Polish researchers said that this process may also affect the polyphenol content of the resulting juice.
“In the case of cloudy apple juice, the suppression of enzymatic browning conditions and the lack of clarification prevent the loss of polyphenols,” they said.
Polyphenols are receiving extensive research due to their potent antioxidant activity, their ability to mop up harmful free radicals, and the associated health benefits. Many have also been implicated in possible protection against diseases such as cancer and cardiovascular disease, while some have been reported to potentially offer protection from Alzheimer’s.
Indeed, lead author Jan Oszmianski reported that clear juice made from the Idared apple variety contained 250mg of polyphenols per litre, while cloudy juice made from the Champion apple variety contained 1044mg per litre.
How the research was done
The radical-scavenging activity of the juices was measured with electron paramagnetic resonance (EPR) spectroscopy using the DPPH (1,1-diphenyl-2-picrylhydrazyl) radical, with the cloudy Champion apple variety juice reported to scavenge 93 percent of the radicals after three minutes, compared to only 24 percent for the clear Idared variety juice.
“Cloudy and clear apple juices differ markedly in their content of procyanidins, which is reflected in their antioxidant capacity and in the rate constant for the DPPH radical-scavenging ability,” said the researchers.
“Owing to the high content of procyanidins, health benefits are expected mainly in the case of cloudy apple juice consumption,” they concluded. - (Decision News Media, January 2007)
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