Soft Drink Sweeteners
The introduction of a sugar taxes as well as health concerns, have led to manufacturers reformulating their soft drinks to less than 5% sugar or ‘no added sugar’ versions. If a low level of sugar is included, it makes sense to use one which provides maximum sweetness – such as fructose. It is the sweetest of the main bulk sugars and has a lower glycaemic index (GI) than sucrose. Fructose is also found in fruit juice and glucose-fructose syrup for example.
A low level of a high intensity sweetener (HIS) is also needed to restore sweetness to the level of the original full sugar drink. HIS are only permitted in soft drinks in the EU if they are ‘energy-reduced’ or ‘no added sugar’ beverages. HIS can also moderate the saltiness of energy drinks designed for rehydration and reduce the perceived bitterness of many other ingredients.
Sugar has a preserving effect and also provides mouthfeel (viscosity), which contributes to a richer, lingering flavour. HIS do not have a thickening or preserving effect. In reduced-sugar drinks, viscosity can be returned by adding a suitable hydrocolloid thickener or soluble fibre. Examples of hydrocolloids are xanthan gum, CMC (cellulose gum) and pectin. Gum Acacia is another type of soluble fibre, and it is also claimed to have a sweetening effect. Inulin and related oligosaccharide fibre has a sweetening effect arising from its fructose content although its poor long-term stability is not suited to acidic drinks.
Consumer ‘energy’ drinks can still achieve low sugar levels with relatively high carbohydrate levels if maltodextrin is used to replace sugar. Maltodextrin has little sweetening effect and a HIS is generally needed in such drinks. Maltodextrins are rated by their ‘DE’ figures or ‘dextrose equivalent’, although this is not a measure of dextrose content or relative sweetness.
High Intensity Sweeteners (HIS)
| HIS | Sweetness* | EU maximum (ppm) | Bitter after-taste |
| Acesulfame K (AceK) | 200 | 350 | ++ |
| Aspartame | 200 | 600 | – |
| Aspartame/acesulfame salt | 350 | 350 | + |
| Cyclamate** | 40 | 250 | + |
| Neohesperidine DC** | 1000 | 50 | ++ |
| Saccharin | 300 | 80 | +++ |
| Steviol glycosides | 150-400 | 80 *** | Depends on type |
| Sucralose | 600 | 300 | – |
* Sweetness relative to sucrose ** Not permitted in the US *** steviol equivalents
Table 1 Some HIS approved for soft drinks in the EU
All approved HIS apart from the steviol glycosides are synthetic. They are used at much lower levels than sugar (Table 1). Their calorific contribution is negligible. HIS vary in permitted use-level, bitter after-taste and flavour profile (the speed that sweetness develops in the mouth, the maximum achievable sweetness and how long it lingers on the palate). The aspartame flavour profile is similar to sucrose, whilst other HIS tend to deviate from the sucrose flavour profile and are sometimes used in combination to achieve a more sucrose-like flavour. A HIS may be used at a several hundred times lower use-level than sucrose – although the maximum attainable sweetness varies from one HIS type to another and may be less than the maximum sweetness achievable by sugar (sucrose). The sweetness rating is therefore an indication of the use-level compared to sugar for a particular sweetness level – it is not an indication of the maximum relative sweetness of different HIS. Once the maximum sweetness for a particular HIS has been achieved – adding more will simply increase any bitter after-taste without increasing sweetness. Aspartame can match the sweetness of a 16% sucrose solution whilst saccharin or a steviol glycoside such as Rebaudioside A for example can only equal the sweetness of a 10% sucrose solution.
HIS are generally process-stable with a good product shelf-life although aspartame is less stable. Aspartame and the aspartame/acesulfame mixed salt are metabolised to phenyl alanine and require a warning label on packaging for phenylketonuria sufferers. Aspartame will undergo Maillard browning with sugar and this can be a problem in some colourless drink applications. Particular attention should be taken when dissolving aspartame – especially in cold water.
The choice of sweetener may be influenced by the overall flavour – saccharin works well with orange. Aspartame is well-suited to fruit flavours in general. Optimising the acid type – can have a positive flavour effect in fruit drinks – malic acid working well in apple and berry systems at the same time as masking HIS off-flavours. Citric acid tends to be used with flavours like lemon and orange.
HIS Combinations
The sweetness of acesulfame K (AceK) develops rapidly on the palate and soon fades. In contrast, sucralose and cyclamate develop sweetness more slowly than AceK (or sucrose) and it lingers longer on the palate. HIS combinations can therefore more closely match the original sucrose flavour profile. There are potential cost savings to be made as a result of synergistic flavour effects; saccharin with cyclamate (+20%) and aspartame with AceK (+30%) are two examples of combinations with increased sweetness. Synergy can also be a way of overcoming sweetness limitations arising from individual maximum permitted HIS levels. HIS combinations with aspartame help off-set its instability.
A bitter after-taste or liquorice-note associated with some HIS is less obvious if there is a low level of sugar present or in combinations where individual HIS are present at lower concentration than when they are used alone (bitter notes tend to be more noticeable at higher HIS use-levels).
Common HIS Combinations include AceK with aspartame (1:1), AceK with sucralose (1:1), cyclamate with saccharin (10:1) and aspartame with saccharin (2:1). Two other examples currently used in the UK are AceK and saccharin (shandy) and saccharin with sucralose (lemonade). One difficulty in developing flavour systems is that after-taste may only become obvious after drinking say a can of drink – rather than tasting a small sample in a kitchen trial.
Natural HIS
The drive for natural ingredients has increased demand for ‘stevia’ – a class of HIS based on steviol glycosides extracted from stevia leaves (stevia rebaudiana). This complex mix includes stevioside and various rebaudiosides. When originally approved, Rebaudioside A and stevioside were specified as the major steviol-based components. This had some deficiencies in sugar-free systems unless boosted by a sweetness enhancer such as enzyme-modified stevia added as ‘flavouring’. The addition of limited amounts of other sweetening agents such as fructose, dextrin and gum acacia can also be used to boost overall sweetness. The stevia specification within the EU was re-defined (EU 2016/1814) to allow Rebaudioside D and M types. These can achieve improved sweetness and reduced bitterness/liquorice-like flavour note in some systems. The permitted use-levels of different steviol glycosides are based on their individual steviol contents. A conversion factor is used to calculate the permitted dose (so-called steviol equivalents).So if a steviol glycoside contains 33.3% by weight steviol, its permitted use-level is three times higher than its steviol content.