3.3.3.1 Glucose
Glucose is not a very good humectant due to the lower water holding capacity (WHC), which makes it difficult to obtain the isotherm curve at low aw.
3.3.3.2 Fructose
Fructose has a higher water activity reduction capacity and therefore is more desirable as a humectant in stabilizing food products.
3.3.3.3 Sucrose
Sucrose is one of the most studied sugars and is widely used in food systems, in the confectionary industry, both in the U.S. and Europe, but has a lower water activity reduction capacity compared to fructose.
The water reduction capacity of sugar and salts in their amorphous and anhydrous state at different aw is presented in Table 3.1.
Table 3.1. Water activity reduction capacities of sugars and salts.
Moisture content (g H2O/100 g Solids)
Anhydrous Amorphous
Sugars aW = 0.60 0.70 0.80 0.90 0.60 0.70 0.80 0.90
Sucrose 3.0 5.0 10.0 - 14.0 20.0 35.0 65.0
Glucose 1.0 3.5 7.5 12.5 1.0 3.5 8.0 22.0
Fructose 14.0 22.0 34.0 47.0 18.0 30.0 44.0 80.0
Lactose 0.01 0.01 0.05 0.10 4.5 4.7 4.7 -
Sorbitol (adsorption) 17.0 22.0 37.0 76.0 2 5.0 3 5.0 5 5.0 110.0
Corn syrup - - - - 1 4.0 2 0.0 3 0.0 54.0
Salts
NaCl (adsorption) 0.1 0.1 130.0 5 85.0 - - - -
NaCl (desorption) - _ 385.0 5 90.0 - - - -
KCl (adsorption) 0.1 0.1 0.1 0.1 - - - -
KCl (desorption) - - 0.1 580.0 - - - -
Source: Sloan and Labuza (1975).
3.3.3.4 Other humectants