Online Exclusive: A Guide to Reb A

Interest in Rebaudioside A, Rebiana, or Reb A, as it is commonly known, has grown exponentially with the recent notification from FDA that it has no objection to its GRAS status as a sweetener. Reb A, at a 95% level of purity or higher, was cleared by FDA in Dec. 2008.

This natural, zero-calorie sweetener has the potential to change the sweetener industry significantly. Reb A comes on to the market at a very opportune time in the United States. The national waistline has never been greater, so the need for a natural substitute to caloric and noncaloric sweeteners is well, natural. Heres a look at what Reb A is, its regulatory status, how its derived and some technical background.

What is Reb A?

Reb A is a completely natural, high-intensity sweetener that is about 350 to 450 times sweeter than sugar. Its found in nature in the leaf of the Stevia Rebaudiana plant, which is native to South America, and where it has been used safely as a sweetener for generations.

While Reb A is derived from the stevia plant, it is not the same as the stevia that has been sold for years in the U.S. as a dietary supplement. Reb A is one of several related sugar-like substances known as steviol-glycosides that are found in the stevia plant, as shown in Table 1. It is one of the sweetest and best-tasting steviol-glycosides.

The regulatory story

GRAS status follows submissions by various food and beverage manufacturers to the FDA, in which the companies had concluded that they had enough documented research information on their particular stevia derivatives to warrant GRAS status. It was already legal to import and grow stevia in the United States, and the sale and consumption of stevia is permitted as a dietary supplement on the basis of its low glycemic index.

Reb A was not previously approved for use in the United States and European Union (EU) due to two factors historically associated with conventional stevia extract. First, there was an issue with the taste profile of steviathe crude extract that was used contains a mixture of approximately 10 different glycosides, not all of which taste good. Second, because the extract contains a mixture of different molecules, it was impossible to give a clear specification of the product. The ratio of molecules in the extract would vary substantially, depending on the climate and weather conditions where the stevia was grown. This variation caused difficulties for food and beverage manufacturers, and more importantly, made it difficult to conduct clinical trials to assess product safety.

These challenges were overcome by PureCircle, Florham Park, NJ, a company that pioneered research into the extraction and refinement of Reb A. The company developed proprietary process technologies to ensure its highly-purified Reb A has a good flavor profile and is a standardized product with standardized characteristics. This enabled clinical trials on the safety of the product to be complete.

In June 2008, the FAO/WHOs Joint Expert Committee on Food Additives (JECFA) convened to consider and evaluate various steviol glycosides and concluded that high-purity Reb A, containing 95% steviol glycosides, is safe for human use. It allocated a permanent Acceptable Daily Intake (ADI) of 0 mg to 4 mg per kg body weight. The importance of the JECFA conclusions should not be underestimated. It paved the way for global clearance of Reb A, and approvals have subsequently been granted in Switzerland, Australia and New Zealand.

Stevia was accepted in Australia and New Zealand following an application made by the Plant Science Group at Central Queensland University and Australian Stevia Mills. In a judgement based on numerous studies from around the world, the plant was approved for commercial use in Australian food and beverage manufacture by the countrys food safety authority, FSANZ, in Oct. 2008. Approvals have subsequently been given in Switzerland, the first European country to do so, and Russia.

Approvals are also expected in the EU, following a Sept. 2007 submission made to the European Food Safety Authority (EFSA).

How Reb A is processed

The stevia plant has been used for many years throughout the world as a natural sweetener. Stevia is a member of the Chrysanthemum family. It grows wild in any warm climate where there are large temperature variations during the day. The plant is hardy, requires little water and has few natural pests. Its cultivation provides significant economic benefits to the local farming communities in which it is grown, because it can be harvested up to four times per year.

After the stevia plants are harvested, they are dried and put through an extraction process. The extraction process follows traditional methods using a freshwater brewing method to unlock the plants natural sweeteners, including Reb A. To minimize waste, once the extraction process is complete, the unwanted mulch and processed leaf is used as fertilizer for the crops.

The crude extract is then refined to isolate out the Reb A. Using proprietary natural crystallization and separation technology, the constituent glycoside molecules in the extract (Table 1) are separated, isolating pure Reb A. The crude extract is made up of about 50% Reb A, the balance or coproduct that is refined out is either recycled or used in the production of other products.

Table 1: Molecular structure, sweetening power and amount of Steviol glycosides in stevia leaves

Na = Not available. a: may be an artifact of the extraction process (Geuns, 2004)

The high-pressure liquid chromatography of Reb A 97% and stevia extract points out the main difference in purity between them, which contributes to sweetness quality in different applications.

Sensory evaluation of Reb A shows a significant improvement in sweetness and reduction in bitterness and sourness against stevia raw extract, and stevioside.

Using Reb A

Reb A offers a number of tangible benefits both to food producers and their customers, making it an ideal mainstream food ingredient. It is 100% natural and is about 350 to 450 times sweeter than sugar, yet has no calories, giving manufacturers the ability to lower the caloric content of their products without adversely affecting taste.

Unlike some other high-intensity sweeteners, Reb A is highly stable at extreme temperatures, making it suitable for cooking, baking and freezing. It is pH-stable, so has a long shelf life, and it does not ferment, making it suitable for use in a wide range of food and beverage products.

Solid Stability: Reb A is very stable. No degradation was observed over the first two years of a five-year storage study at room temperature at 60% relative humidity.

Solution Stability: In solution, Reb A is most stable between a pH value of 3 to 8, and noticeably less stable below a pH of 2. Stability decreases with increasing temperature. It is noteworthy that the hydrolytic breakdown products of Reb A are steviol glycosides, which are sweet, and thus the loss of sweetness is negligible over the normal shelf life period. Reb A is photostable; no degradation is observed on light exposure.

Temperature & pH stability: Reb A is fairly acid stable at a pH of 3 and above at a high temperature, as shown in the following graph.

The following graph shows the stability of Reb A solution (0.5%) in different acid systems after 120 days at room temperature.

In the United States, it is currently being considered by manufacturers for use in tomato ketchup, cereals, ice cream, hard candy, chewing gum and chocolate. In Asia, it is an established ingredient in soy sauce, beverages, and many foods including kimchi. In summary, Reb A offers food and beverage manufacturers an all-natural, zero calorie, readily processable alternative to sugar, high fructose corn syrup and synthetic sweeteners.

With its zero-calorie content combined with an excellent taste profile, Reb A is an ideal option for consumers to use as part of a balanced and calorie-controlled diet without compromising on taste.

Application Specifics

In commercial beverages (pH 3.6), Reb A remains fairly stable after 12 months of storage.

Applications: Reb A, being a premium, natural, high-intensity, no-calorie sweetener, is an excellent choice for a wide range of food products, including: tabletop sweetener for tea, coffee, etc.; beverages, including carbonated soft drinks, still beverages and powdered soft drinks; dairy, such as ice creams, yogurts and sherbets; baked goods, including cakes, biscuits, cereals and bars; jams, sauces and pickles; sweet desserts and puddings; confections and chewing gum; seafood; and vegetables. Plus, it can be used in products for general weight loss and diabetics.

The following table lists selected product categories containing different amounts of sugar. The Reb A concentration noted is the typical usage level when used as a single sweetener. The Reb A usage level may vary, depending on the formulation, flavor, co-sweetener, and target consumers.

Blending with Reb A

Blending of certain sweeteners provides sweetness synergy in food applications. Besides sweetness synergy, blend can also affect the flavor, sweetness profiles and whole-mouth experience of consuming food. A wide range of both caloric and noncaloric sweeteners can be blended with Reb A to provide earlier onset of sweetness, fuller mouthfeel and reduction of aftertaste. Some examples of caloric sweeteners that contribute to better mouthfeel are sugar, fructose, HFCS, sugar alcohols (e.g. sorbitol, maltitol and xylitol). Some of the amino acids (e.g. glycine, alanine and serine) can also improve the overall sweetness profile of Reb A.

Reb A will only provide sweetness and so must be used in combination with a bulking agent, which replaces the bulk of the sugar. Selection and optimization of the correct combination of bulking agents to give the required physical and textural characteristics is the challenge that calls for expertise of food scientists. In reduced sugar applications, the suggested bulk sugar replacers are sugar alcohols (sorbitol, maltitol or lactitol), fiber (e.g. polydextrose, soluble corn fiber, inulin, FOS, oat fiber, etc.), maltodextrin and corn syrup solids. Addition of a bulking agent may affect flow and thermal characteristics (viscosity, osmolality, water mobility, glass transition, temperature, etc.) of product during and after processing.

Healthy Reb A

Reb A is suitable for consumption by diabetics as it has a low glycemic index and may therefore be used in foods formulated for this market. It is non-cariogenic, so reduces the risk of tooth decay and cavities. It is both nontoxic and non-carcinogenic. Importantly it also meets todays informed consumers preference for natural and healthy ingredients.

Research studies have demonstrated a number of other health benefits in the use of Reb A. It has been shown to have a beneficial effect on blood sugar levels and is effective in lowering blood pressure. Additionally research indicates that it significantly increases glucose tolerance and inhibits glucose absorption.

Pricing

It is difficult to make a direct comparison between Reb A and sugar. While Reb A is more expensive per kilo; the fact that it is between 350 to 450 times sweeter must be taken into account. It is also predicted that the increased levels of commercial production required to meet market demand following GRAS status will result in significant economies of scale and an associated price reduction for the product.

Demand for biofuels and continuing price increases of both high fructose corn syrup and sugar have also created favorable market conditions for Reb A.

Summary

Natural high-intensity, non-nutritive sweetener

Excellent taste350 to 450 times sweeter than sugar

Soluble in water (0.8% solubility in water) and alcohol bases

High stability in acid and alkaline solutions (pH 3-9)

High tolerance to temperature up to 200 C

High stability under light

Greater sweetness prolongation vs. sugar

Sweetness stability in all production processing conditions

Outstanding storage and shelf life properties and ability to withstand normal warehouse conditions

Flavor enhancer used with either salt, organic acids or amino acids, e.g. fruity flavor

Nontoxic; extensively tested in animals and extensively used by humans with no adverse effects

Sugarless with no calories; will not affect blood sugar levels and so highly recommended for diabetics

Sidd Purkayastha, Ph.D., is the Technical Director of Pure Circle, USA. Prior to joining PureCircle, he worked for more than 20 years at Tate & Lyle. Dr. Purkayastha has broad experience in the structure-function of food ingredients, including sweeteners, starch, acids and hydrocolloids. He earned his doctorate in food engineering from the University of Massachusetts and an M.B.A. from the University of Illinois.

PureCircle (LSE:PURE) is the worlds leading producer of high-purity Rebaudioside A (Reb A), with a vertically integrated supply chain operating in three continents. Activities range from the sourcing of dry stevia leaves and extraction, refining of Reb A into sweeteners and marketing of these sweeteners to food and beverage manufacturers worldwide.