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Analysis of soft drinks containing sugar and Stevia
Relevant for: Beverage manufacturers
More and more beverages are sweetened with a combination of sugar and Stevia for reasons of healthy calorie reduction. Whether the soft drink contains sugar or sugar plus Stevia, Anton Paar instruments easily cope!
How much sugar is good for you?
Not only products like chocolate, ice cream, jams and cakes contain saccharose, commonly referred to as sugar, but also many convenience food products and beverages. Especially soft drinks represent a large source of “hidden” sugar. Many consumers prefer soft drinks with less sugar. It is not only the calorie intake linked to obesity, but also a health concern that causes consumers to decide on sugar-reduced drinks. Overweight and obesity are major risk factors for a number of chronic diseases. They also increase risks of coronary heart disease and type 2 diabetes. The World Health Organization (WHO) recently reduced the recommended daily intake to 25 grams of sugar which corresponds to approximately six teaspoons per day for adults, and for children only half of this amount.
Why partially replace sugar?
The problem: A regular soft drink contains 8 to 10 grams of sugar in 100 mL, so an average size can of regular soft drink might already exceed the recommended maximum daily sugar intake.
The question: As the sweetening power of Stevia exceeds the sweetness of saccharose by far, the required amount of Stevia to achieve the same degree of sweetness in soft drinks is much lower, thus the calorie intake almost negligible. On top of that, sweeteners such as Stevia do not promote caries. So why not replace the entire sugar content in soft drinks with sweeteners?
The answer: It is the mouth feel and the taste that make consumers prefer sugar-sweetened beverages.
The solution: Beverages with a combination of sugar and sweetener mean less sugar while maintaining the full-bodied taste.
What is Stevia?
A commonly used sweetener with soft drink manufacturers is the highly water soluble steviol glycoside Rebaudioside A (see Figure 1), for the sake of simplicity referred to as Stevia in this report, which will subsequently be considered in more detail.
The sweetening power of Stevia is estimated to be at least 200 times higher than that of sugar, another reference mentions a sweetening power of 300 to 450. In other words, the amount of 0.01 g Stevia in 100 mL is as sweet as at least 2 g of sugar in 100 mL (or 2 °Brix).
Will addition of Stevia to regular soft drinks affect the measurement results?
The determination of density, based on the U-tube method, and the calculation of °Brix therefrom is a well established procedure among soft drink producers. If also °Brix fresh, °Brix inverted and the degree of inversion are required, a Soft Drink Analyzer M (SDA M), containing a density and a sound velocity cell, is the perfect instrument for fast and correct measurement results and reliable quality control. The following measurements show that results are equally correct and reliable if instead of only sugar a mixture of sugar and Stevia is dissolved in the soft drink. Stevia (Sigma Aldrich, Rebaudioside A ≥ 96 % (HPLC) 01432-10G) was added to distilled water and two different commercially available regular Cola beverages (Cola 1 and Cola 2). Investigations were carried out with an SDA M at 20 °C. Repetitive determinations were performed.
Addition of Stevia to water
Figure 2 shows that the addition of 0.0978 g of Stevia to 100 mL of distilled water causes a °Brix raise of 0.078 °Brix (mean of 5 determinations).
Addition of Stevia to regular Cola beverages
To investigate the influence of Stevia on regular soft drinks, the degassed samples Cola 1 and Cola 2 were investigated. Measurements of Cola 1 and Cola 2 were performed without and with (compare Table 1) the addition of Stevia.
|Stevia added to Cola 1 [g/100 mL]||Stevia added to Cola 2 [g/100 mL]|
Figure 3 graphically displays the results of Cola 1 without and with Stevia. Figure 4 graphically displays the °Brix results of Cola 2 without and with Stevia.
°Brix fresh, °Brix actual and degree of inversion: The direct comparison
Three measurements of degassed Cola 1 without addition of Stevia (Solution 1, compare Table 1) were performed. 0.0187 g Stevia were added to 100 mL of degassed Cola 1 from the same bottle. This solution (Solution 2) which has a sweetening power of at least 3.7 °Brix up to 8.4 °Brix, was measured four times. All measurements were carried out with SDA M and an Xsample 122 Sample Changer.
Figure 5 graphically displays the obtained results on °Brix actual, °Brix fresh and °Brix inverted of Cola 1 samples without (Solution 1) and with addition of Stevia (Solution 2).
Summary and conclusion
As expected, the density increase caused by addition of Stevia manifests itself in a small increase of °Brix. Repetitive determinations were carried out for each measurement. Addition of 0.0978 g of Stevia to 100 mL of distilled water shows a value of 0.078 °Brix (Figure 2). Similar amounts of Stevia added to degassed Cola 1 (0.1002 g) and Cola 2 (0.0984 g) showed an increase of 0.078 °Brix and 0.093 °Brix, respectively. Figure 3 and Figure 4 show the influence of different amounts of added Stevia to Cola 1 and Cola 2, the trend lines in these figures show linearity for both Cola samples. This fact indicates that the °Brix measurement with SDA M of soft drinks containing both sugar and Stevia is accurate. An example is presented in Figure 5: Cola 1 was investigated with an added amount of Stevia that has a sweetening power of at least 3.7 °Brix up to 8.4 °Brix. This corresponds to the sweetness that is expected to be found in Cola beverages in today’s supermarket shelves. Comparing the differences in °Brix actual, °Brix fresh and °Brix inverted of Cola 1 with and without Stevia leads to the conclusion that the added amount of Stevia does not have a noticeable influence. The deviations of the results on samples with and without addition of Stevia are well below the instrument’s specifications.
The instrument employed in this study was an SDA M with a density and a sound velocity cell. From the results it can also be deduced that a DMA™ M density meter is equally suitable to cope with soft drinks that contain an combination of sugar and Stevia.