Fruit juices contain more vitamin C than their labels indicate

[Guest guest]

Fruit juices contain more vitamin C than their labels indicate

http://www.eurekalert.org/pub_releases/2009-10/f-sf-fjc100509.php

A team of pharmacists from the University of Santiago de Compostela (USC) has

established that the levels of vitamin C in many fruit juices and soft drinks

are far higher than those indicated on their labels by the manufacturers. This

finding has been possible owing to a new technique developed by the researchers

to determine the content of vitamin C in these kinds of drinks.

Ascorbic acid or vitamin C is a natural antioxidant in fruits and vegetables,

but the European Commission permits its use as an additive in juices, jams,

dairy products and other foods. The involvement of this substance in the immune

response and other biochemical processes such as the formation of collagen and

the absorption of iron is well-known. However, high levels of ascorbic acid can

cause diarrhoea and gastrointestinal problems, as a result of which scientists

are attempting to determine the content of vitamin C in foods with greater and

greater accuracy.

Now, a group of researchers from the Faculty of Pharmacy of the USC has

developed a new chromatographic technique (these are used to separate and

identify chemical elements) aimed at accurately measuring the ascorbic acid in

fruit juices and soft drinks. By applying this method, they have found that the

amounts of vitamin C stipulated on the labels of many drinks are not real. In a

sample of 17 fruit juices, soft drinks and isotonic drinks, only two correspond

to what is indicated on the bottle.

Ana Rodríguez Bernaldo de Quirós is a member of the team which has developed the

new technique, whose details have recently been published in the Food Chemistry

magazine. " The other drinks contain much higher levels than those specified by

the manufacturer because, as has already been indicated in a previous study, the

label probably only shows the amount of added ascorbic acid, without taking into

account the fruit's natural vitamin C content " , she explained to SINC.

Bernaldo de Quirós highlights the greater resolution and sensitivity of the

method, by means of which it is possible to detect up to 0.01 milligrams of

vitamin C per litre, " thanks to the use of new column chromatography, based on

spherical particles of ultra pure silica 3 microns in size " .

" Another advantage of the method is its simplicity and speed, as the total time

taken to carry out the analyses is no more than six minutes " , the researcher

remarked.

With the new technique, the valuation of the ascorbic acid in the drinks has

revealed some curious data. Of the 17 samples analyzed, the one with the highest

vitamin C content was an apple juice (840 mg/l), more than the orange juices

(352-739 mg/l). The results for the pineapple and grape juices were 702 mg/l and

between 30.2 and 261 mg/l for the soft drinks (orange, lemon and apple).

The researchers also evaluated how the vitamin C content of the orange juices

and tea drinks varies while they are on the shelves in the temperature

conditions specified by the manufacturer. After six days, the former barely lose

8% of their ascorbic acid while, in the tea drinks, this substance falls by 54%

at 4ºC and practically disappears at room temperature.

###

References:

A. Rodríguez-Bernaldo de Quirós, M. Fernández-Arias, J. López-Hernández. " A

screening method for the determination of ascorbic acid in fruit juices and soft

drinks " . Food Chemistry 116 (2): 509-512, 2009.