01 May 2016 Study: Not all SA orange juices are equally healthy

This is according to Dr Cindy Hunlun (below), who has done the first investigative study of its kind in South Africa on the content and health value of locally produced orange juice.

Dr Hunlun was awarded with a doctorate in food science on this subject by Stellenbosch University (SU) in March.

Dr Hunlun worked in the juice industry for five years before being appointed as lecturer at the Cape Peninsula University of Technology (CPUT) and thereafter starting work on her doctorate. Her supervisor was Dr Gunnar Sigge of the SU Department of Food Science. He was assisted by Dr Dalene de Beer and Prof Jessy van Wyk.

According to Sigge, quite a lot of work has been done in the agricultural industry on the cultivation and packaging of citrus fruit, but local research into its health value has been minimal.

As much as two million tons of oranges are harvested annually for the export market and local consumption. Some of these are also processed into value-added products, such as orange juice.

As part of her research, Hunlun carefully investigated the chemical and phenolic content (which influences nutritional value) of three orange varieties that are cultivated on a large scale in South Africa. These are the varieties Mandarin, Navel and Valencia.

She also compared the content of frozen orange concentrate, the juice which is eventually made from it, and freshly squeezed juice. The anti-oxidant levels, which are a measure of good health value, were also ascertained for each.

She collected orange juice samples from two cultivation areas (the Western and Eastern Cape) over three seasons. It was analysed to ascertain what influence variety, seasonality and cultivation area can have on fruit content. The way in which the fruit was handled after harvesting can also have an influence.

Hunlun found, among other things, that the anti-oxidant levels of Eastern Cape oranges are higher than that of fruit produced in the Western Cape, and that it therefore has more nutritional value. These aspects are also higher in locally produced Navel and Valencia oranges than in Mandarins.

Concentrate prevails

Most orange juice in South African shops is made from concentrate which is frozen and then sold to juice producers. Hunlun found that such juice had appreciably less health value than a glass of freshly squeezed juice. The freshly squeezed option enjoyed higher phenolic levels and contained more anti-oxidants than concentrate versions.

“If you are in search of the maximum amount of health value in a glass of orange juice, it is best to drink freshly squeezed juice,” Hunlun advises.

The formulation of juice is determined by Department of Agriculture legislation, which allows for juice of a specific fruit type such as orange to be diluted by up to 50% with other fruit  juices – typically apple, pear or grape or a combination – and be sold being described as, for example, Orange “100% juice blend”.

“In the process, however, this drink loses many of the healthy characteristics which consumers assume are part of the juice made from a specific kind of fruit,” Hunlun says.

“Many juice formulations only include the minimum amount of orange juice allowed by law – 50% – possibly due to cost as well as the high acidity of citrus.

“So to make it sweeter they add other fruit juices,” she adds. “My recommendation would be to increase the minimum percentage of the named fruit to perhaps 80%.”

Source: Faculty of Agrisciences, Stellenbosch University; www.ecr.co.za

You can listen to an interview with Hunlun on Cape Talk here