Nature's sweeteners: stevia isn't the half of it

In a market dominated by high-intensity artificial sweeteners, the pressure to differentiate products means the use of the 'natural' claim is a tempting one. Mark J Tallon, PhD, surveys the stevia landscape — and predicts the next sweetener category to follow.

Laborer/IStockPhotoA market driven by lesser-evil foods — including 'low in,' 'free from' and 'a good source of' — suggests that the use of nonsynthetic ingredients is a key to boosting sales and product profile.

The current sweetener challenge for today's food technologists is to reduce calories while maintaining the taste/flavour profile of sugar (sucrose). Today we understand the cellular components of taste better than in the past. As part of this development, industry now offers a diverse range of natural and synthetic sweeteners, which, when combined with enhancers and formulated into foods and beverages, are a close sugar mimic. We still don't have the perfect substitute, but we are getting close. In the March 2007 and June 2006 issues of Functional Ingredients (then Functional Foods & Nutraceuticals), I referred to two sweetener options including stevia and a sweet-tasting protein. It seems those insights are now major factors in the sweetener market in 2009. The following article takes a closer look at these issues and what the implications are for the wider sweetener market.

REB-A: the big change in natural for 2009
If you have had the blinders on over the past 12 months, you may have just about missed the hype surrounding the natural sweetener extracted from Stevia rebaudiana Bertoni (a member of the chrysanthemum family). The plant was discovered by natives of Paraguay who used extracts of its leaves to sweeten the bitter drink called maté. In 1931, French researchers then isolated the sweet components from the stevia leaf known as steviol glycosides, of which stevioside and rebaudioside A (Reb-A) are the most abundant.

This low-cal, low-glycaemic, natural sweetener with a profile delivering 200-400 times sweeter taste than sugar catapults it to the top of the chain in meeting the demands of today's health-conscious consumer. Additionally, research suggests stevia has antioxidant,1 anti-inflammatory,2 antiglycaemic3 and antihypertensive properties.4 These factors fit well with the results from the 2007 Mintel (Chicago) report, "Sugar and Sweeteners — US," which showed significant consumer interest in sugar alternatives that offer health benefits — such as prolonged energy and boosted immunity — and sweeteners fortified with vitamins and minerals, especially in 18-24 year olds.

In 2004, a selection of safety studies were commissioned by Cargill on its Reb-A extract (Truvia).5,6 These trials confirmed earlier human studies demonstrating safety with consumption equivalent to a 68kg person drinking 1000-2000oz of Reb-A equivalent.7,8,9 Taken in their entirety the results show no negative effects on health based on the toxicological profile, according to Cargill's website. In line with these findings, the FDA in December 2008 permitted the use of Cargill's Reb-A extract as generally recognized as safe (GRAS) for use as a general-purpose sweetener. Although only recently granted GRAS status in the US, stevia already dominates more than 40 per cent of Japan's sweetener market — a sign of things to come in the West, perhaps?

The real winner from the GRAS approval is Cargill's raw-ingredients supplier PureCircle, a UK-listed holding company headquartered in Bermuda with a purification plant in Malaysia. PureCircle has not only aligned itself with Cargill (and its partner Coca-Cola) but also with Pepsi for sale under the brand PureVia. Since the announcement of GRAS status and its new partnerships PureCircle's share price has doubled.

The future for stevia will not only be in offering a natural, high-intensity sweetener, but in also offering functional benefits, which already seem to be taking form in recent scientific publications.1,2,3,4

Protein power: sweetness beyond '09?
The search for the sugar alternative has continued with many offerings from both the natural and synthetic worlds. However, one segment of nature's sweetener-selection box still remains almost completely uncommercialised: 'sweet proteins.' Despite the identification of at least seven sweet proteins — including thaumatin, monellin, mabinlin, pentadin, brazzein, curculin, and miraculin — only two have finally been brought to market.10 Talin (thaumatin from Nutraceutical Group, Spain) and Cweet (brazzein from Natur Research Ingredients (NRI) are sweet proteins that have sweetness factors of 3,000 and 2,000 times that of sugar, respectively.11,12

Brazzein is a sweet protein found in the fruit of a West African plant (Pentadipandra brazzeana Baillon), and carries a taste similar to sugar cane. Of all the sweet proteins, brazzein is the smallest (22kda) and is very heat and pH stable, meaning its application as a sweetener could extend across many food and beverage categories. In 2007 Natur Research Ingredients launched Talin, its brazzein brand. However, its success is unknown as I was not able to receive details on product launches or sales. Despite this, the company is looking toward 2010 in which additional sweet proteins with a higher taste profile are in the development pipeline. According to a recent statement from Loren Miles, CEO of NRI, "Attempts to commercialise brazzein failed because no practical manufacturing process was ever developed to help it reach the marketplace."

Thaumatins are a class of intensely sweet proteins isolated from the fruit of Thaumatococcus danielli (grown in West Africa). Unlike brazzein, thaumatin is slightly less robust upon heating, and at pH 7.0 and 70oC its sweetness dissipates and starts to aggregate.13,14 Despite some potential limitations, a dose of 2,000mg/kg/day over a 13-week assessment period demonstrated no toxicity, suggesting its safety potential for use in foods.15 As yet, little is still understood or disclosed regarding thaumatin's commercial success despite its initial launch circa 1998 when Talin was sold by Tate & Lyle. To date we have little knowledge regarding its functional attributes for health other than its low-calorie, low-glycaemic profile.

When sweeteners collide
The future of sweeteners could be a blend of artificial and natural sweeteners. However, in today's market think may not be the only solution. Recent work suggests sweet proteins can be manipulated by removing or adding certain extracts that possess short- and long-term sweetness, as well as any residual aftertaste. Already we have seen some commercial applications in extract technologies in the form of Reb-A, the sweetest component extract of the stevia plant.

The next sweetener targets will be sweet proteins. Already Japan has approved these for use as additives in many foods, which are driving the commercial machine for innovation and new applications. The main issue is not isolating and characterising these proteins, but rather manufacturing and commercialisation. This is the next challenge for food technologists.

There already is a move toward new taste solutions as many feel we have gone as far as we can with synthetic and often non-nutritive sweeteners. So food science is switching its focus to sweetness enhancers in the form of natural fruit extracts that can be used directly on foods, or in combination with sweeteners. As we move through 2009-2011, stevia will increasingly dominate the market, as will other functional sweeteners such as isomaltose (and natural polyols such as erythritol) and prebiotic fibres.

Despite the 130,000 tonnes of sugar currently produced every year in the developed world, its dominance will decline in the face of its continued associations with obesity and diabetes. As long as the market is increasingly driven by health and wellness, the move to natural, organic and functional is the order of the day, with sweet proteins vying for top spot.

Mark J Tallon, PhD, is the founder of NutriSciences, a London-based consultancy firm specialising in health-claim substantiation, product development and technical writing.

1. Ghanta S, et al. Oxidative DNA damage preventive activity and antioxidant potential of Stevia rebaudiana (Bertoni), a natural sweetener. J Agric Food Chem 2007;55(26):10962-7. 2. Boonkaewwan C, et al. Anti-inflammatory and immunomodulatory activities of stevioside and Its metabolite steviol on THP-1 cells. J Agric Food Chem 2006; 54(3):785-9. 3. Gregersen S, et al. Antihyperglycemic effects of stevioside in type 2 diabetic subjects. Metabolism 2004; 53(1):73-6. 4. Hsieh MH, et al. Efficacy and tolerability of oral stevioside in patients with mild essential hypertension: a two-year, randomized, placebo-controlled study. Clin Ther 2003; 25(11):2797-808. 5. Maki KC, et al. Chronic consumption of rebaudioside A, a steviol glycoside, in men and women with type 2 diabetes mellitus. Food Chem Toxicol 2008; 46(7):S47-53. 6. Maki KC, et al. The hemodynamic effects of rebaudioside A in healthy adults with normal and low-normal blood pressure. Food Chem Toxicol 2008; 46(7): S40-6. 7. Curry LL, et al. Subchronic toxicity of rebaudioside A. Food Chem Toxicol 2008; 46 Suppl 7:S11-20. 8. Das S, et al. Evaluation of the cariogenic potential of the intense natural sweeteners stevioside and rebaudioside A. Caries Res 1992; 26(5):363-6. 9. Curry LL, et al. Rebaudioside A: two-generation reproductive toxicity study in rats. Food Chem Toxicol 2008; 46(7):S21-30. 10. Kant R. Sweet proteins ? potential replacement for artificial low calorie sweeteners. Nutr J 2005; 9(4):5. 11. Ogata C, et al. Crystal structure of the intensely sweet protein monellin. Nature 1987; 328(6132):739-42. 12. Izawa H, et al. Synthesis and characterization of the sweet protein brazzein. Biopolymers 1996; 39(1):95-101. 13. McPherson A, et al. X-ray analysis of new crystal forms of the sweet protein thaumatin. J Biomol Struct Dyn 1990; 7(5):1053-60. 14. Kaneko R, et al. Heat-induced formation of intermolecular disulfide linkages between thaumatin molecules that do not contain cysteine residues. J Agric Food Chem 1999; 47(12):4950-5. 15. Higginbotham JD, et al. Safety evaluation of thaumatin (Talin protein). Food Chem Toxicol 1983; 21(6):815-23.

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