There are different properties of starch-derived sweeteners, such as carbohydrate profiles, solids, viscosity, color, fermentability, foam stabilization, gel strength, freezing point depression, boiling point elevation, gelatinization temperature, humectancy, hygroscopicity, crystallization, and sweetness. These properties affect by the degree of conversion, enzyme treatment, solids level, types of sugars, and other factors.
The physical properties of sweeteners change based on their degree of conversion, which was previously measured using DE. However, advances in enzyme technology and the use of different carbohydrate profiles have made DE less important in describing syrup nature. Instead, liquid chromatography is used to analyze the syrup’s carbohydrates and their effect on physical properties.
The carbohydrate profile of a syrup heavily affects its physical properties, and this profile is determined by the type of conversion and enzyme treatment. Enzyme treatments can create sweeteners with different carbohydrate profiles but the same DE value, so multiple descriptors are often used, such as “43 DE, high-maltose syrup.” This becomes important when discussing functional differences and applications of starch-derived sweeteners.
Syrups are identified by their degree of conversion (DE), carbohydrate profile, and solids level. The Baume number is the traditional way to express the solids of a glucose syrup. However, for high-fructose syrups, the solids content is stated as the dry substance.
When measuring the solids content of glucose syrups, refractometers calibrated in degrees Brix are commonly used. However, some correction must be applied to obtain the true solids level. Brix measurements refer to the percentage of sucrose in solution and have been modified over time resulting in minor changes. High-fructose syrup tables commonly used in the beverage industry incorporate these corrections.
Glucose syrups are like Newtonian fluids, which means they have a constant coefficient of viscosity measured in poises. Viscosity in sweeteners made from starch depends on the solids level and the percentage of higher saccharides present. Sweeteners with longer chains of molecules and weak hydrogen bonds have higher viscosity than sweeteners with high concentrations of monosaccharides, even at the same solids level.
Browning Reaction and Color
Starch-derived sweeteners are often described as “water white”, but their color is better measured in terms of optical density (absorbance). The color of corn sweeteners, like high-fructose and dextrose syrups, is typically measured by comparing their absorbance against a reference standard of water at 450 nm and 600 nm. Sweeteners can turn brown due to several reactions, such as reacting with proteins and amino acids, or caramelization due to heat or acids. The more reducing sugars present, the faster color develops. This can be helpful in baking, but can also lead to undesirable flavors if overcooked. Color development can be slowed by using sweeteners with less monosaccharides or by demineralizing the sweetener.
Starch-based sweeteners are easily fermentable and widely used in industry. The fermentability of these syrups by yeast depends on their content of simple sugars. The fermentable extract value of a sweetener is usually calculated by adding the amounts of different types of sugar present. However, the actual values may differ slightly from the theoretical ones. Glucose and fructose have different fermentation pathways, and high levels of glucose can hinder the mechanism for utilizing maltose and maltotriose.
Foam Stabilization and Gel Strength
Low DE sweeteners can stabilize foam structures in whipped and aerated products due to their high polysaccharide content and hydrogen bonding. The concentration and type of sweetener can also regulate water availability, affecting the gel-sol transition process. Syrups with high soluble solids concentrations can be used to achieve gelation of high methoxyl pectin solutions for making jams, jellies, and preserves. Using glucose syrups can result in firmer gels than using high-fructose syrups.
Freezing Point Depression
Sweeteners affect the freezing point of solutions they are added to. The lower the average molecular weight of the sweetener, the greater the effect on the freezing point. Lower conversion syrups affect the freezing point less than higher conversion syrups. The effect of sweeteners on the freezing point also depends on the solids level. Sweeteners can also control the formation of ice crystals by controlling the movement of free water, acting as stabilizers.
Boiling Point Elevation
The sweetness of a sweetener affects its boiling point and the more sweet the sweetener is, the higher its boiling point.
The concentration and replacement of sweeteners in baking can affect the temperature at which starch granules gelatinize. Replacing sucrose with fructose lowers the gelatinization temperature. Sweeteners also lower water activity, form sugar bridges between starch chains, and have an anti-plasticizing effect compared to water.
Humectancy and Hygroscopicity
A hygroscopic material takes in moisture from the air, while a humectant material resists changes in moisture content. The amount of moisture a corn syrup gains or loses depends on the humidity of the surrounding air.
Starch syrups can crystallize, which can be good for making hard candy but not for making jam. Syrup helps make jelly by increasing the solids level, which prevents microbial growth and helps it maintain a clear structure. Sweetener also binds water and makes it gel. The level of crystallizing sugars like dextrose must be controlled, as too much can cause crystallization during storage.
Sweetness is an important characteristic of sweeteners. Shallenberger defines sweetness as a primary taste and states that no two substances can have the same taste as sucrose. However, the relative sweetness of various sweeteners can be compared. The sweetness onset, duration, and intensity vary for different sweeteners due to factors such as chirality, molecular weight, viscosity, solids level, and isomers present. Fructose can exist in different forms, with β-D-fructopyranose being the sweetest at cold temperatures, but fructofuranose forms predominate at hot temperatures, resulting in lower perceived sweetness.
Selection of Sweeteners
Sweetener selection for food applications depends on cost, availability, and functional properties. Sometimes, the desired properties cannot be found in a single sweetener. For instance, a sweetener may need to have both high sweetness and high viscosity. In such cases, blends of sweeteners or other food ingredients are needed.