PRODUCT RESEARCH UPDATE – MAY 2011

The SA Rooibos Council supports several researchers at local universities and science councils to explore the quality and health properties of Rooibos. The scientific evidence that they produce is crucial to substantiate health claims of Rooibos, and provides a basis for the development of new value-added Rooibos products.

The following product research projects are currently supported:

Developing objective quality and sensory parameters for Rooibos
Research leader: Professor Lizette Joubert, Agricultural Research Council

This project aims to characterise a typical cup of Rooibos according to its total polyphenol content, the major individual flavonoids and antioxidant capacity. The research team is analysing hundreds of Rooibos tea samples from different regions and seasons, from 2009 into 2011.

A key finding so far is that pasteurisation decreases chemical parameters and colour values for Rooibos tea. The researchers were also able to demonstrate that high quality Rooibos (as measured by its sensory attributes such as taste and mouthfeel) has higher levels of soluble solids and total polyphenols.

This research is complemented by a project aimed at a comprehensive description of the taste, flavour and aroma of Rooibos, and the development of a “flavour and mouth-feel wheel” to support the local and international Rooibos trade. THRIP (Technology and Human Resources for Industry Programme) is a co-funder. Professor Joubert presented the latest version of the flavour wheel at the Research Day on 17 May 2011.

The influence of Rooibos on stress
Research leader: Professor Amanda Swart, Stellenbosch University

Rooibos is widely used as a herbal tea for enhancing well-being, supporting the immune system and combating stress. During stress, which is characterised by anxiety, sleeplessness and depression, there is an increased production of stress hormones. Professor Swart’s project looks at the influence of Rooibos on the biosynthesis of cortisol, since the inhibition of cortisol biosynthesis may alleviate stress symptoms, thus validating the anti-stress potential of Rooibos.

So far her team has been able to show that Rooibos decreases the levels of corticosterone in rats (the equivalent hormone in humans is cortisol, the so-called “stress hormone”). Rooibos is further able to enhance the inactivation of corticosterone to an inactive metabolite. This finding may have clinical applications in the treatment of hypertension and metabolic syndrome. Interestingly enough, they also found that Rooibos increases testosterone levels in male rats.

Rooibos and exercise
Research leader: Professor Jeanine Marnewick, Cape Peninsula University of Technology

Antioxidants play a vital role in protecting tissues from excessive oxidative damage during exercise. With this project, Professor Marnewick and her team want to determine whether the antioxidants in Rooibos, already found to protect the body against other conditions linked to oxidative stress, can also help to protect against exercise-induced oxidative stress, including biochemical damage and inflammatory responses in cells. They will look at the effect of Rooibos on sport performance in a group of volunteers who will take part in several acute exercise regimes. Between 30 and 40 volunteers will take part in the clinical trial during this project. The project kicked off in 2010, but requires an extensive amount of preparatory and analytical work, and therefore there are no findings to report yet.

What exactly is in a cup of Rooibos tea?
Research leader: Professor Andrew Marston, University of the Free State

Despite extensive studies on the polyphenols in Rooibos, relatively little is known about the polar fraction of the tea that is composed largely of polysaccharides and tannins. This study focuses on that part of the chemical makeup of Rooibos, and may in future help us understand how these components influence the sensory characteristics of the tea, as well as how they contribute to its health properties, including an influence on resistance to disease, cancer prevention and ageing.

The researchers prepared a polysaccharide-rich fraction of Rooibos tea and demonstrated – for the first time – that this fraction of Rooibos could stimulate the immune system (or has an immunomodulatory effect). They are now busy with further isolation of the different polysaccharides, characterizing them and testing the activity of the individual polysaccharides.

As far as the tannin-rich fraction of Rooibos is concerned, the team is using high-performance countercurrent chromatography to isolate these tannin compounds. They will then determine the structures of these tannins and study their biological activities.

Investigating the cancer-prevention properties of South African herbal teas
Research leader: Professor Wentzel Gelderblom, Medical Research Council

The complex mix of antioxidants in Rooibos is able to delay or prevent several kinds of cancer, and helps to protect us against carcinogens in our environment. Prof Gelderblom and his team are trying to unravel the complex interactions that take place in living cells to help us to understand how Rooibos achieves this cancer preventing effect. New data on the cancer preventing properties of green rooibos provide new opportunities in developing a product to protect against the effect of UV light-induced cell damage in the skin. This is a long-term project that has been ongoing at the MRC (with co-funding from many partners) for more than ten years.

The microbiological quality and safety of Rooibos
Research leader: Professor Pieter Gouws, University of the Western Cape

Prof Gouws and his team investigate the influence of processing on the microbiological quality of Rooibos. They look at how different microorganisms may be able to survive and even multiply during steps such as fermentation and steam pasteurisation and storage. They are focusing specifically on organisms that may be of public health concern. The aim is to advise the industry on critical control points (CCP) in a Hazard Analysis Critical Control Point (HACCP) system.

Could Rooibos help to battle the bulge?
Research leader: Professor Johan Louw, Medical Research Council

Worldwide there is a growing interest in the role of polyphenols (chemical substances found in plants) in the fight against obesity. Rooibos is rich in polyphenols and could potentially help to battle the bulge. This new project kicks off in 2011 and will investigate the impact of Rooibos extract on satiety, as well as the processes whereby the body stores and breaks down fat.

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