Sweet foods and drink are consumed far in excess of their value in relieving hunger and thirst. As a species we like and demand the sweet taste or sensation and a large sector of the food industry is concerned solely with the production of foodstuffs to meet this need. Traditionally sucrose and later glucose syrups were the sweeteners of choice for such foods and whilst these versatile raw materials are still widely used, artificial sweeteners are playing an ever increasing role in the foods we eat. The measurement of sweetness is not straightforward in the way that other parameters of glucose syrups are measured. There are no instrumental means of assessing sweetness and human tasters or assessors must be used with their associated errors. Trained taste panels can eliminate many of these and provided control of factors such as temperature of tasting, concentration and methodology is made, absolute and comparative values for sweetness can be obtained. As far as glucose syrups are concerned two general statements regarding sweetness can be made:
- sweetness increases as DE increases at the same concentration
- sweetness increases as concentration increases at the same DE (up to saturation sweetness).
Additionally it is known that sweetness increases as tasting temperature increases and decreases with increasing acidity and lowering of pH. Additionally, the more viscous a solution the less sweet it tastes owing to impaired access of the sweetener to the taste receptor. All these factors are of course very important and vary widely in food systems although when assessing the sweetness of a product they are normally closely controlled. It is thus essential that not only is sweetness measured under closely controlled conditions to provide absolute values but also assessed in the actual finished product in which the sweetener is used.
The table below shows the sweetness values of a range of glucose syrups and related products using sucrose as the standard. For glucose syrups threshold sweetness is inversely related to DE (logarithmically) and directly related to molecular weight (logarithmically).
|15 DE glucose syrup
|25 DE glucose syrup
|37 DE glucose syrup
|43 DE glucose syrup
|52 DE glucose syrup
|64 DE glucose syrup
|78 DE glucose syrup
|86 DE glucose syrup
|High fructose glucose syrup
It has been reported in the literature that components of glucose syrups with a molecular weight equal to or greater than maltotriose (DP3) possess little or no sweetness although some workers consider DP7 to be the cutoff point (Kimura and Nakakuki, 1990). This would imply that the sweetness of glucose syrups is mainly proportional to their glucose and maltose contents. Glucose syrups do however possess a sweetness greater than the sum of their glucose and maltose contents and synergistic reactions between components have been used to explain the effect.
Recent public interest in generally healthier lifestyles has resulted in changes in the diet, leading to the increased consumption of foods which are perceived as having beneficial physiological effects. One aspect of this has been the increased consumption of sugar-free confectionery. These products are considered non-cariogenic and contain fewer calories than the sweets they replace. In many cases they are also suitable for diabetics as they require no insulin for their metabolism.
Traditionally, sucrose and glucose syrups (with fats and texture modifiers as appropriate) have been used to produce confectionery. Sugar-free products are manufactured from sugar alcohols (hydrogenated derivatives of reducing sugars) the most commonly used being sorbitol, although others such as maltitol, isomalt and xylitol are widely used. The process of hydrogenation leads in some cases to quite dramatic increases in sweetness, for example with maltitol (Kearsley et al., 1980).
High fructose corn syrup, produced by the isomerization of a 90-95 DE glucose syrup (relative sweetness of approximately 60) contains about 42% fructose, 52% dextrose and 6% maltose. In the EU this is used mainly as a direct replacement for sugar in some soft drinks since it is approximately iso-sweet with sugar. The complete dominance of the soft drink market by HFGS and its wider application in Europe is limited not by its properties but by the production quota system in force in the EU.
Several fructose syrup suppliers now offer a range of lower fructose-containing syrups to extend their quota and although these are of reduced sweetness compared with the traditional 42% product they are still nevertheless used to replace sugar in many products owing to the demand for reduced sweetness foods.
In the USA where there are no restrictions on fructose production, the manufacture and use of fructose-containing syrups has developed into a second phase from the 42% fructose product (Bujake, 1986). A 55% fructose-containing syrup is now the industry norm and this has virtually eliminated the traditional soft drink sweetener, medium invert sugar, from the soft drink market in the USA as well as having successes in areas such as ice cream and baking. Additionally US producers also market 90% fructose syrups which are widely used in dairy products, salad dressings and canned fruits for example where they are used to provide sweetness but with reduced calories owing to the higher sweetness of the product compared with sucrose. The 55% fructose syrup has a sweetness of 99 and the 90% fructose a sweetness of 106 compared with sucrose (White, 1992).