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Rooibus extract may boost acai's health punch

By Stephen Daniells , 29-Oct-2009
Last updated on 29-Oct-2009 at 14:07 GMT2009-10-29T14:07:35Z

Formulating açai products with extracts from rooibus tea may enhance the colour and improve the stability of açai’s healthy components, suggests a new study from Texas.

Flavone-C-glycosides from rooibus tea improved the anthocyanin colour of açai products by up to 46 per cent, and the stability of these compounds by about 40 per cent, according to findings published in Food Chemistry.

“Results suggest flavone-C-glycosides are a potential alternative for the food and beverage industry for their use as colour enhancers and stabilizing agents in products containing non-acylated cyanidin glycosides, particularly açai fruit juice blends and beverages,” wrote Lisbeth Pacheco-Palencia and Stephen Talcott from Texas A&M University.

Açai berries (pronounced ah-sigh-ee) have long formed part of the staple diet of Indian tribes. With the appearance of a purple grape and taste of a tropical berry, it has been shown to have powerful antioxidant properties thanks to a high level of anthocyanins, pigments that are also present in red wine.

It is presently being sold in a number of countries, including New Zealand, Australia, South America, Japan, USA, and the Middle East

In order to enhance the berry’s anthocyanin content, which play a role in both the colour and antioxidant activity, the Texas-based researchers investigated the effects of different classes of naturally occurring and externally added polyphenols.

Using a model system based on açai fruit with a cyanidin-3-rutinoside content of 311 milligrams per litre and a cyanidin-3-glucoside content of 208 mg/l, Pacheco-Palencia and Talcott examined the effects of the açai alone, or in combination with flavone-C-glycosides rich extracts, including a commercial rosemary extract (ColourEnhance, Naturex) and Rooibos tea extracts obtained by brewing loose rooibos tea (Keekanne

GmbH, Germany).

Results showed that anthocyanins did indeed degrade over time, due to pH and temperature of storage.

“The presence of flavone-C-glycosides induced significant [colour enhancement] and enhanced anthocyanin stability at all pH and temperature combinations, while no significant effects were attributed to the presence of phenolic acids or procyanidins,” wrote the researchers.

Addition of the rooibos tea extracts led to 46 per cent higher anthocyanin colour and 41 per cent increased anthocyanin stability compared to the control, they added, and these results were similar to those obtained using the commercial rosemary-based colour enhancer.

“Thus, addition of rooibos extracts, rich in flavone-C-glycosides, not only resulted in higher colour intensities but also increased anthocyanin stability during long-term storage (30 °C) of açai anthocyanin models, in a comparable manner to a known copigment source such as rosemary extract,” wrote Pacheco-Palencia and Talcott.

“Results from model systems can be related to similar effects in natural açai juices, and are thus indicative of the potential of flavone-C-glycoside-rich extracts for anthocyanin stabilization in açai-containing foods, juice blends and beverages.”

Source: Food Chemistry
Volume 118, Issue 1, Pages 17-25
“Chemical stability of açai fruit (Euterpe oleracea Mart.) anthocyanins as influenced by naturally occurring and externally added polyphenolic cofactors in model systems”
Authors: L.A. Pacheco-Palencia, S.T. Talcott

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