According to market analyst Mintel, apple juice consumption is on the up, with sales in the UK up 43 per cent between 2003 and 2006, from 95 to 136 million litres.
Consumer trends currently favour clear over cloudy apple juice consumption, with consumers reported to prefer the clear variety, apparently based on the conception that it is purer.
However, the new research from scientists at the Agricultural University of Wroclaw and the Medical University of Warsaw states that the polyphenol content of cloudy apple juice is four times that of the clear juice.
The production of clear apple juice involves addition of 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 250 milligrams of polyphenols per litre, while cloudy juice made from the Champion apple variety contained 1044 milligrams per litre.
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 per cent of the radicals after three minutes, compared to only 24 per cent 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.
The research was welcomed by Lucy Ede, head of products at the juice company Innocent, who reportedly already use cloudy apple juice in their products. Ede told the Chemistry & Industry magazine: "Cloudy juices taste better and have amazing body, which is important for us. But the fact that cloudy juices have more health benefits is extra exciting and definitely encourages us to use them."
Source: Journal of the Science of Food and Agriculture doi: 10.1002/jsfa.2707 "Comparative study of polyphenolic content and antiradical activity of cloudy and clear apple juices" Authors: J. Oszmianski, M. Wolniak, A. Wojdylo, I. Wawer