Chemical and Functional Properties of Food Saccharides

Solubility of fructans in aqueous media is governed by their molecular structure
and variations in temperature of the solvent. The more symmetric the fructan, the
harder is its solubility; the more branched, mixed-type the fructan, the easier and
better is the solubility. Also, higher the temperature of the solvent, better the solubility
of the fructan. Highly symmetric inulin tends to form crystalline structures,
and elevated temperatures between 50 and 80˚C are needed to obtain a solution.
However, once dissolved, such solutions are stable even at room temperature.
Figure 13.3 presents the degradation of aqueous solution of high-molecularweight
inulin from chicory (10 mg/ml) at 80˚C. Stability of the molecular composition
after 3 days was very high, but after 7 days the molecular weight distribution
decreased in low-molecular-weight components and the fructose portion increased
about fivefold. Nevertheless, even at room temperatures, inulin swells in an aqueous
Mass Fraction
© 2004 by CRC Press LLC
1.5
1.2
0.9
0.6
0.3
0
0.4 0.8 1.2 1.6
lg(dp)
FIGURE 13.3 Distribution (m_dpD_d) of high-molecular-weight fractions of chicory inulin
according to their degree of polymerization (DP) determined calibrated size-exclusion chromatography
(SEC at 80°C). ææ: initial inulin (t = 0 days), mean values of DP from
m_dpD_d are DP w = 21, DP n = 14 (including mono- and disaccharides); ææ: 3 days 80˚C,
mean values of DP from m_dpD_d are DP w = 16, DP n = 9 (including mono- and disaccharides);
ææ: 7 days at 80˚C, mean values of DP from m_tdpD_d are DP w = 8, DP n = 5 (including
mono- and disaccharides). SEC column system: precolumn (Fractogel HW40; 10 ¥100 mm)
+ Superose 12 (10 ¥ 300 mm) + 2¥ Fractogel HW40 (10 ¥ 300 mm); eluent: 0.05 mol/l
NaCl; flowrate: 0.6 ml/min; injection volume of sample: 0.1 ml of 0.1% carbohydrate; mass
detection by DRI; internal standard for flow control: 2 mg NaCl/ml; SEC calibration: dextran
20, dextran 1 (Pharmacosmos, DK) and sucrose; data processing with CODAwin32 and
CPCwin32 (a.h group, Graz, Austria).