Chemical and Functional Properties of Food Saccharides

© 2004 by CRC Press LLC
methods, such as multivariate data, discriminant and principal component analysis,
artificial neural network, and principal variables, it was shown that modified starches
can be qualitatively and quantitatively differentiated. 7,8 Starch gelatinization or melting
and the subsequent retrogradation processes (gelation, syneresis, helix formation,
crystallization) are of great importance to the quality of products.
Studies that used sample techniques such as diffuse reflectance (DRIFT) and
attenuated total reflectance (ATR) showed the usefulness of IR for the determination
of conformational changes during processing and storage. But absolute determination
of the conformation of starch is still not possible. The O–H stretching vibrations
between 3000 and 3700 cm –1 and the C–C and C–O stretching and C–O–H bending
vibrations between 800 and 1300 cm –1 are sensitive to conformation, short-range
order, crystallinity, and hydration. 7–9 Recently, the relationship between baking behavior
and chemical structure of cassava starch was studied with IR 10 (Figure 23.1).
23.2.1.3 Other Polysaccharides
Pectins have a backbone of (1→4)-linked α-D-galacturonan with side chains of α-
D-galactopyranose, α-L-arabinofuranose, and α-(1→2) rhamnopyranosyl residues.
Most studies focused on the carboxyl groups in pectic derivatives or the degree of
esterification of carbonyl groups in pectins. 7,11,12 Characteristic band shifts of the
C=O ring, and the symmetric or asymmetric carboxylate vibrations showed the
interaction of divalent cations with pectate or pectinate, indicating a metal coordination
in agreement with the egg-box hypothesis and complex formation.
Xylan structure depends on the nature of the xylopyranan backbone, β-(1→4)
or β-(1→3), and the presence of glucuronic acid side chains and arabinose. This
results in marked spectral differences, which depend on water content, sorption, and
hydration. 7 It was shown that water influences the molecular orientation and degree
of ordering. Spectral features of (1→4) xylans are affected by the α-L-arabinofuranose
substitution of the C-3, but not significantly by arabinofuranose or glucuronic
120 100 80 60 40 20 0
Chemical shift (ppm)
FIGURE 23.1 Solid-state 13 C-CP/MAS NMR spectrum of pregelatinized waxy corn starch.