Stevia plant derived Rebiana is significantly more potent in cold water, finds a US based team who flag up their findings as critical for developers of low-calorie products to get the right sweetness level when replacing sugar with the natural sweetener.
Rebiana is a zero-calorie, natural, high-potency sweetener (HPS) derived from the leaves of Stevia rebaudiana Bertoni and comprising almost pure rebaudioside A.
It has had generally recognized as safe (GRAS) status in the US since December 2008 and is becoming a popular alternative to caloric sweeteners in both reduced- and no added-sugar products.
Scientists, writing in the Journal of Food Science, said their results indicate that rebiana is more potent in the cold than at room temperature, an important practical consideration for the formulation of the many products using rebiana and intended to be consumed refrigerated.
The Rebiana used, said the authors, was supplied by Cargill Health & Nutrition. It comprised 97.9% rebaudioside A, 1.3% rebaudioside D, 0.7% rebaudioside B, and 0.1% stevioside (dry basis).
Rebiana, they authors note, is particularly suited to nonalcoholic beverages and dairy products such as yogurt, ice-cream, and flavoured milk.
They add that reliable information on its sweetness concentration-response (C-R) behavior is fundamental to rebiana's use as an ingredient.
But the authors claim that most researchers only cite single potency figures. “These are of little value to product developers because, in common with other HPS, the C-R of rebiana is not a straight line and its potency varies with concentration,” commented the scientists.
The researchers measured the sweetness of rebiana over a range of concentrations at room and refrigerator temperatures. They explained that the response curve of rebiana in room-temperature (21 °C) and refrigerated (5 °C) water was determined using 2-alternative forced choice discrimination tests with a minimum of 70 tasters, all untrained Cargill administration staff.
The sucrose used in the study was Domino brand granulated cane sugar, they added.
Solutions for room temperature tasting were made on the day of tasting and held for between 2 and 6 hours, said the scientists. Over the period of the study rebiana was dissolved in water to make 7 solutions of accurately-known concentration in the range 60 to 600 mg/L. Samples to be tasted cold were made similarly and stored overnight in a refrigerator to be tasted the next day, they added.
Samples were served as pairs of solutions, about 30 mL of each in 60 mL (2 oz) plastic portion cups. All solutions, the team continued, were presented at room temperature (21 ± 1 °C) or cold (5 ± 0.5 °C).
From a series of panels the proportion of tasters finding different sucrose concentrations sweeter than a fixed concentration of rebiana was plotted against sucrose concentration, said the team.
“The resultant sigmoid curves were linearized by transforming the ordinate axis to a probability scale, to aid experimental design and determination of isosweet concentrations. Isosweet concentrations of sucrose for seven rebiana concentrations up to 600 mg/L were used to construct a C-R curve for each temperature,” explained the food scientists.
The authors concluded that rebiana is more potent in the cold than at room temperature. It seems likely, they added, that rebiana's sweetness is governed by the relative amounts of different conformers in solution and that these are temperature-dependent.
The researchers note that their findings are contrary to the findings of Schiffman and others (2000) who used relatively small panels of 8 to 17 tasters to rate rebaudioside A at different temperatures by a sweetness matching technique.
“These researchers chose 50 °C for their warm samples and compared them to solutions at 6 °C. Thus, it could be that rebaudioside A tastes sweeter both above and below 21 °C, and that it is relatively sweeter at 50 °C than at 6 °C, but this remains to be confirmed,” added the authors.
As a footnote, the scientists note that steviol glycosides are known to have non-sweet side tastes, often described as licorice or bitter but clarified that an assessment of this aspect was outside the scope of this study, but they report that such data “is available elsewhere.”
Source: Journal of Food Science
Published online ahead of print DOI: 10.1111/j.1750-3841.2011.02414.x
Title: Sweetness concentration-response behavior of rebiana at room and refrigerator temperatures
Authors: John C. Fry, Nese Yurttas, Kari L. Biermann