Study suggests Roselle could provide industrially viable quantities of natural red colour

By Nathan Gray

- Last updated on GMT

Related tags Leatherhead

A Hibiscus herb species known as Roselle may be a good source of natural red pigments for applications in the food industry, according to new research investigating the extraction of anthocyanins from the species.

The study, published in the Journal of Food Engineering​, investigated the influence of extraction parameters on the isolation of the natural red pigment anthocyanin from the Hibiscus sabdariffa​ (Roselle) herb - with the authors noting that the search for optimal operating conditions to maximize the efficiency of anthocyanin extraction from the plant “is necessary for industrial application.”

The team, led by senior author Professor Manuel Dornier at the Centre for Agricultural Research for Development (CIRAD), France, reported that a maximum yield of 88% anthocyanin can be obtained from Roselle and noted that solid-to-solvent ratio and particle size have the strongest effect on the extraction yield.

Dornier and his team reported that ‘interesting’ and potentially industrially viable results were obtained with a solid to solvent ratio as low as 1/5 when using crushed Roselle calyces at 25 °C.

The team noted that “an extraction yield of 63% and an anthocyanin concentration of 0.3 grams per litre could be obtained in less than 10 minutes.”

Natural growth

The world market for natural colours has increased by more than 29% in value terms since 2006, with annual growth levels having hovered around the double-digit mark until very recently, according to Leatherhead Food International.

During this time, it said the share of the global food colours market taken by natural varieties increased from around 33% in 2006 to 37.2% in 2010.

“The natural colours market remains one of the best performing sectors within the world market for additives and ingredients, due to the strong interest in natural colours, and the well-publicised concerns over the use of some synthetic colours,”​ claimed Leatherhead in a report last month.

Roselle red

Many parts of the Roselle herb are used in foods, among them the fleshy red calyces are the most popular, and have been reported to be used in the production of wine, juice, jam, jelly, syrup, and tea.

The red calyces which also contain antioxidants including flavonoids, gossypetine, hibiscetine and sabdaretine and are reported to have antihypertensive properties, however they are increasingly exported to America and Europe for use as food colourings due to their high content of anthocyanins.

Study details

Dornier and his team noted that after initial modelling, crushed Roselle calyces at an average diameter of 150 μm were used “to increase the extraction efficiency while reducing extraction times.”

The researchers added that at this particle size the concentration of anthocyanins reached equilibrium in the early minutes of extraction, and only increased yield by between 1 and 3% over the next two hours:

“Whatever the solid-to-solvent ratio, the extraction of anthocyanins was mainly achieved during thefirst ten minutes,”​ they affirmed.

The team used the 150 μm Roselle powder to then find the optimal extraction parameters for extraction in terms of temperature and solid to solvent ratio – revealing that increasing the solid-to-solvent ratio increased anthocyanin extraction yield, whilst temperature had no clear effect.

Dornier and his colleagues reported that a maximum yield of 88% anthocyanins was obtained at 25 °C with the highest solid-to-solvent ratio (1/25), whilst an extraction yield of 63% and an anthocyanin concentration of 0.3 grams per litre could be obtained from a solid-to-solvent ratio as low as 1/5 in under ten minutes.

The researchers concluded that Roselle calyces are a good source of anthocyanins “with several potential applications in the food, pharmaceutical and cosmetic industries.”

Source: Journal of Food Engineering
Published online ahead of print, doi: 10.1016/j.jfoodeng.2011.10.012
“Aqueous extraction of anthocyanins from Hibiscus sabdariffa: experimental kinetics and modelling”
Authors: M. Cissé, P. Bohuon, F. Sambe, C. Kane, M. Sakho, M. Dornier

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