Fructose

The sweetness of fructose is perceived earlier than that of sucrose or dextrose, and the taste
sensation reaches a peak (higher than sucrose) and diminishes more quickly than sucrose.
Fructose can also enhance other flavors in the system. One of the problems of Processed
fructose is that people use the same amount as sucrose sugar and it is too much.
Sweetness synergy
Fructose exhibits a sweetness synergy effect when used in combination with other sweeteners. The
relative sweetness of fructose blended with sucrose, aspartame, or saccharin is perceived to be
greater than the sweetness calculated from individual components.
Fructose solubility and crystallization
Fructose has higher solubility than other sugars as well as other sugar alcohols. Fructose is
therefore difficult to crystallize from an aqueous solution. Sugar mixes containing fructose, such as
candies, are softer than those containing other sugars because of the greater solubility of fructose.
Fructose hygroscopicity and humectancy
Fructose is quicker to absorb moisture and slower to release it to the environment than sucrose,
dextrose, or other nutritive sweeteners. Fructose is an excellent humectant and retains moisture
for a long period of time even at low relative humidity (RH). Therefore, fructose can contribute to
improved quality, better texture, and longer shelf life to the food products in which it is used.
Freezing point
Fructose has a greater effect on freezing point depression than disaccharides or oligosaccharides,
which may protect the integrity of cell walls of fruit by reducing ice crystal formation. However,
this characteristic may be undesirable in soft-serve or hard-frozen dairy desserts.
Fructose and starch functionality in food systems
Fructose increases starch viscosity more rapidly and achieves a higher final viscosity than sucrose
because fructose lowers the temperature required during gelatinizing of starch, causing a greater
final viscosity.
Food sources
Natural sources of fructose include fruits, vegetables (including sugar cane), and honey. Fructose
is often further concentrated from these sources. The highest dietary sources of fructose, besides
pure crystalline fructose, are foods containing table sugar (sucrose), high-fructose corn syrup,
agave nectar, honey, molasses, maple syrup, and fruit juices, as these have the highest percentages
of fructose (including fructose in sucrose) per serving compared to other common foods and
ingredients. Fructose exists in foods either as a free monosaccharide, or bound to glucose as
sucrose, a disaccharide. Fructose, glucose, and sucrose may all be present in a food; however,
different foods will have varying levels of each of these three sugars.The sugar contents of common
fruits and vegetables are presented in Table 1. In general, in foods that contain free fructose, the
ratio of fructose to glucose is approximately 1:1; that is, foods with fructose usually contain about
an equal amount of free glucose. A value that is above 1 indicates a higher proportion of fructose
to glucose, and below 1, a lower proportion. Some fruits have larger proportions of fructose to
glucose compared to others. For example, apples and pears contain more than twice as much free
fructose as glucose, while for apricots the proportion is less than half as much fructose as glucose.
Apple and pear juices are of particular interest to pediatricians because the high
concentrations of free fructose in these juices can cause diarrhea in children. The cells
(enterocytes) that line children's small intestines have less affinity for fructose absorption
than for glucose and sucrose. Unabsorbed fructose creates higher osmolarity in the small
intestine, which draws water into the gastrointestinal tract, resulting in osmotic diarrhea. This
phenomenon is discussed in greater detail in the Health Effects section.
Table 1 also shows the amount of sucrose found in common fruits and vegetables. Sugar cane
and sugar beet have a high concentration of sucrose, and are used for commercial preparation of
pure sucrose. Extracted cane or beet juice is clarified, removing impurities; and concentrated by
removing excess water. The end product is 99.9% pure sucrose. Sucrose-containing sugars include
common table white granulated sugar and powdered sugar, as well as brown sugar.
Table 1. Sugar content of selected common plant foods (g/100g)
Food Item
Total
Carbohydrate
Total
Sugars
Free
Fructose
Free
Glucose
Sucrose
Fructose/
Glucose
Ratio
Sucrose
as a %
of Total
Sugars
Fruits
Apple 13.8 10.4 5.9 2.4 2.1 2.0 19.9
Apricot 11.1 9.2 0.9 2.4 5.9 0.7 63.5
Banana 22.8 12.2 4.9 5.0 2.4 1.0 20.0
Grapes 18.1 15.5 8.1 7.2 0.2 1.1 1.0
Peach 9.5 8.4 1.5 2.0 4.8 0.9 56.7
Pineapple 13.1 9.9 2.1 1.7 6.0 1.1 60.8
Pear 15.5 9.8 6.2 2.8 0.8 2.1 8.0
Vegetables
Beet, Red 9.6 6.8 0.1 0.1 6.5 1.0 96.2
Carrot 9.6 4.7 0.6 0.6 3.6 1.0 70.0
Corn, Sweet 19.0 3.2 0.5 0.5 2.1 1.0 64.0
Red Pepper, 6.0 4.2 2.3 1.9 0.0 1.2 0.0
Sweet
O n i o n , 7.6 5.0 2.0 2.3 0.7 0.9 14.3
Sweet
S w e e t 20.1 4.2 0.7 1.0 2.5 0.9 60.3
Potato
Yam 27.9 0.5 tr tr tr na tr
Sugar Cane 13 - 18 0.2 – 1.0 0.2 – 1.0 11 - 16 1.0 100
Sugar Beet 17 - 18 0.1 – 0.5 0.1 – 0.5 16 - 17 1.0 100
112 113