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The science of stevia

By Stephen Daniells , 30-Apr-2009
Last updated on 07-May-2009 at 18:11 GMT

The science of stevia

There has been much excitement about the promise of stevia as a natural alternative to artificial zero-calorie sweeteners. FoodNavigator.com summarises the science so far.

Interest in the sweetener has been intense, particularly since the FDA issued its non-objection in December that the stevia-derived sweetener Reb A is generally recognized as safe (GRAS) as a food additive.

Differentiation must be made between rebaudiside A and steviol glycosides in general. Rebaudioside A, also known as Reb A and rebiana, is a high-intensity sweetener derived from the stevia leaf. It is said to be approximately 200 times sweeter than sugar.

Safety

The majority of the science around stevia and rebaudioside A are related to its safety. A significant body of research was published online in the peer-reviewed journal Food and Chemical Toxicology (July 2008, Vol. 46, Supplement 1, Pages S1-S92), which found that rebiana - a high-purity Rebaudioside A from stevia - is safe for use as a sweetener for foods and beverages.

An overview in the journal’s supplement by scientists from Coca-Cola, Cargill, and an independent toxicologist said that the studies found the ingredient met all current JEFCA (Joint FAO/WHO Expert Committee on Food Additives) specifications for steviol glycosides.

“The due diligence of the rebiana scientific program reported in this Supplement reflects a commitment by industry partners to, at long last, fully address regulatory requirements for this naturally occurring sweetener by providing the scientific basis to conclude high purity rebaudioside A (rebiana), produced under current GMP to food-grade standards, is safe and appropriate for introduction into the global marketplace,” they concluded.

The FDA issued letters of no objection to GRAS (generally recognized as safe) status for stevia-based Reb A at 95 percent purity or above in December.

Flavour masking

Scientists have also been exploring ways to mask the liquorice or bitter flavours associated with the Reb A stevia extract. The problematic aftertaste has presented difficulties for companies wishing to use the sweetener, and flavour companies have been trying to find ways to mask it without detracting from the perceived benefits of its natural status.

Cargill recently announced a dual-layered approach, starting with its patented technology examining taste responses to Reb A “at a cellular level” and then developing flavour solutions based on these findings.

Comax Flavors released a natural masking flavour in March to mask the bitter aftertaste associated with stevia-derived sweetener Reb A.

A month earlier, Givaudan claimed that it had discovered the bitter taste receptors for stevia, allowing it to focus its flavour ingredients research on blocking the mechanism of these receptors.

The company has said that it is in the process of applying for patents related to the discovery.

Firmenich is also active in the area, having signed an exclusive global collaboration with Reb A supplier PureCircle to provide a formula for applications using the stevia-derived sweetener.

Firmenich said in January that it has developed innovative flavor systems for Reb A, which will be rolled out across food and beverage applications.

Patrick Firmenich, CEO of Firmenich, said: “Reducing sugar in food and beverage products, while maintaining consumer preference, is one of the biggest challenges in our business today.

"By combining PureCircle’s know-how in Reb A with Firmenich’s expertise in sweetness enhancement and flavor masking, I believe that we can fulfill consumer desires for great tasting, low sugar, low calorie foods and beverages.”


Photo-stability

In September a new study from Coca-Cola reported that its high purity stevia extract (rebaudioside A) does not degrade in beverages on exposure to light. Published in the Journal of Agricultural and Food Chemistry, this research was seen as important for establishing the stability of the Stevia rebaudiana (Bertoni)-derived sweetener rebaudioside A.

The results also challenge an earlier study from the 1980s that reported significant degradation of rebaudioside A on exposure to sunlight, equivalent to one week of sunlight during the summer.

To read the article about the study, click here.

Health benefits

Stevia glycosides (SGs) have been reported to not only sweeten but also have some health benefits, including effects on blood pressure and blood sugar levels. Indeed, these observations formed the basis of a citizen’s petition filed by a Washington DC-based law firm called Coburn & Coffman PLLC.

The petition, filed in October, focused on § 301(ll) of the Federal Food, Drug, and Cosmetic Act (FFDCA), and was made on the grounds that SGs have been studied for therapeutic uses, thereby contending that SGs are drugs and therefore cannot be legally added to conventional foods.

In December, FDA concluded that it had no objection to rebiana, (Reb A) at 95 percent purity or above, having GRAS (generally recognized as safe) status as a general purpose sweetener for food and drink, not just as a supplement.

Other health benefits include a report from Indian researchers in 2007 that stevia may also be a rich source of antioxidants and may protect against DNA damage and cancer.

According to findings in the Journal of Agricultural and Food Chemistry (2007, Vol. 55, pp 10962-10967), researchers led by Srijani Ghanta from the Indian Institute of Chemical Biology in Kolkata reported that an extract from Stevia rebaudiana leaves was found to contain an abundance of antioxidant polyphenols, including quercitrin, apigenin, and kaempferol.

Ghanta and his co-workers used methanol and ethyl acetate for the extraction, Subsequent tests showed that the extract could protect against DNA strand scission by hydroxide radicals.

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