Sweetness is one of the five basic tastes and is universally regarded as a pleasurable experience. Ice cream and similar products have a characteristic sweet taste that is critical to product quality. Traditionally the major sweetener used was sucrose. Other sweeteners including glucose, glucose or corn syrups, fructose syrups, fructose, in addition to honey and maple syrup are also used. These sweeteners are referred to as nutritive sweeteners. Other non-nutritive sweeteners e.g. aspartame may also be used. What is sweetness? How is it measured? How can it be controlled?
Ice cream can contain a wide range of sucrose concentrations, typically ranging from 8% to around 20%. Because sweeteners other than sucrose can be used it is usual to express sweetness of ice cream, as relative sweetness (also known as theoretical sweetness), sweetness of individual sweeteners is expressed relative to sucrose which has a reference value of 1.
Relative sweetness is calculated by taking the relative sweetness of individual sweeteners (lactose is normally omitted) and multiplying this by their concentrations or usage rate (g/100g) in the ice cream mix. The individual calculations are summed to give the relative sweetness.
While relative sweetness is widely used in commercial ice cream production the determination of sweetness is largely subjective, so sweetness is not a precise scientific term.
Limitations of relative sweetness
Sweeteners differ in the quality of sweetness and the intensity of taste produced. Sucrose is an ideal sweetener in that it maintains a pleasant taste over the concentration range used in ice cream. The sweetness of fructose is perceived earlier than glucose or sucrose, it quickly reaches peak sweetness and the sweetness fades faster than sucrose.
The colour of a food can affect our perception of sweetness as can the smell or odour. The sweetness of a sugar also changes with concentration hence relative sweetness determinations are only valid at certain sugar concentrations. Acidity will also influence the perception of sweetness. A few substances alter the way sweet taste is perceived, we can call them sweetness modifiers. One class of these inhibits the perception of sweet tastes, whether from sugars or from highly potent sweeteners. Commercially, the most important of these is lactisole, a compound produced by Domino Sugar. It is used in some jellies and other fruit preserves to bring out their fruit flavors by suppressing their otherwise strong sweetness.
Relative sweetness also ignores sweetener interactions and the subjective assessment of taste panellists and consumers. While the limitations of relative sweetness are well known scientifically these not always well understood in commercial ice cream production. Nevertheless, relative sweetness is still a useful product development tool providing its limitations are understood.
Sweetness of various compounds
Sucrose: 1.00 (reference)
Sodium cyclamate: 26
Steviol glycoside: 40-300
Sodium saccharin: 300-675
Lugduname: 300,000 (estimated)
Calculating relative sweetness
Relative sweetness is calculated by taking the relative sweetness of individual sweeteners and multiplying these values by their concentrations in 100g of ice cream mix. For example:
Calculate the relative sweetness of an ice cream containing 16% sucrose and 2% glucose.
One hundred grams of ice cream mix will contain 16 grams of sucrose and 2 grams of glucose.
Since sucrose has a value of 1, the sucrose equivalent of this sweetener is 16 x1 =16
Taking the sucrose equivalent of glucose as 0.8 (Glucose: 0.74-0.8, take the value 0.8); the sucrose equivalent of 2 grams of glucose is 2 x 0.8= 1.6.
Adding both values gives a total sucrose equivalent of 17.6.
If the manufacturer decided to reduce cost by reducing the sucrose concentration then a combination of other sweeteners could be used to give an equivalent relative sweetness. This works fairly well providing it is only the sweetener ingredients that are changed.
However, if glucose, fructose or high fructose syrups are used they may significantly depress the freezing point depression (FPD) of the mix resulting in softer ice cream. While the DE value provides an approximate estimate of sweetness, relative sweetness values provided by the manufacturer of the syrup should be used if available. In the absence of advice from the manufacturer use the DE value to obtain an estimate of the sucrose equivalent of glucose syrup; multiply the DE as a percentage (or decimal) times the sucrose equivalent of glucose. For example:
Calculate the relative sweetness of an ice cream containing 14% sucrose and 8 % of a 30 DE glucose syrup.
One hundred grams of ice cream mix will contain 14 grams of sucrose and 8 grams of glucose syrup.
Since sucrose has a value of 1, the sucrose equivalent of this sweetener in the mix is 14 x 1 = 14.
Taking the sucrose equivalent of a DE 30 syrup as 0.3 x the value for glucose, the sucrose equivalent of 8 grams of 30 DE syrup may be estimated as
8 x 0.8 (sucrose equivalent of glucose) x 0.3 = 1.92. Adding both values this gives a total sucrose equivalent of 15.92.
This approach is widely used in commercial ice cream manufacture in the UK, Ireland and North America. However, relative sweetness is only a guide or tool and further work may be required to modify the relative sweetness of ice cream of a particular flavour so that it has a similar actual or real sweetness when eaten to other flavours. Manufacturers must also be aware of regional preferences and adjust relative sweetness to meet these needs e.g. people in the South of Italy prefer slightly sweeter gelato to those in the North.
A similar method “Potere Dolcificante” (POD) or measure of sweetness is used in Italy and some other continental European countries. POD values differ from relative sweetness values in that the sweetness due to lactose(Lactose: 0.16) is included. For example:
Calculate the POD value of an ice cream containing 56% whole milk, 10% skim milk powder, 16% sucrose and 5% fructose.
One hundred grams of ice cream mix will contain 56 g of whole milk, 10 g of skim milk powder, 16 grams of sucrose and 5 grams of fructose.
Whole milk contains 4.5/100 (estimated lactose concentration in milk) x 56 = 2.52 g lactose
Skim milk powder contains 52/100 (estimated lactose concentration in skim milk powder) x 10 = 5.2 g lactose
Total lactose = 7.72g
POD lactose = 7.72 x 0.16 = 1.24
The ice cream also contains 16 grams of sucrose and 5 grams of fructose(Fructose: 1.17-1.75, take the value 1.7).
POD sucrose = 16 x 1 = 16
POD fructose = 5 x 1.7 = 8.5
Total POD = 25.74