Chemistry Reference
In-Depth Information
elucidation of complex products is needed (see Thelwall, 1997). Yanahira et al.
(1995) examined the composition and structure of galactosaccharides using
methylation analysis, mass spectrometry and NMR spectroscopy. Lemoine
et al. (1997) carried out extensive studies using NMR spectroscopy to examine
the structures of extracellular polysaccharides of S. thermophilus. Boehm and
Stahl (2003) have provided an excellent overview of analytical methods suitable
for glyco-conjugates present in milk. They review methods for chromatography,
mass spectrometry, spectroscopy, electrophoresis and separation techniques,
such as crystallization and filtration.
Traditionally, dietary fibre was considered to comprise largely of plant
cell walls, namely cellulose and lignin (Van Soest, 1978). Southgate et al.
(1978) defined dietary fibre as ''the sum of lignin and the polysaccharides that
are not digested by the endogenous secretions of the human digestive tract''.
This physiologically based definition includes both water-soluble and -inso-
luble constituents. Thus, fructo- and galacto-oligosaccharides and possibly
other prebiotic carbohydrates would be considered as ''dietary fibre''. Appro-
priate methods of analysis of the water-soluble components have long been a
challenge for analysts. Thebaudin et al. (1997) discussed the heterogeneous
composition of this fraction and methods of analysis in more detail. The 1998
Codex guidelines on food labelling defined dietary fibre as ''edible plant or
animal material not hydrolysed by the endogenous enzymes of the human
digestive tract'' (Codex Alimentarius, 1998). The historical development of
the dietary fibre concept, its definition and the ensuing development of
suitable analytical methods has been discussed extensively (AACC, 2001;
IFST, 2007). The present accepted definition, which has been adopted widely
by food regulators and manufacturers, includes generalized health benefits
based mainly on epidemiological data generated primarily from studies using
fruits, vegetables and whole grain cereal foods. This definition is
Dietary fiber is the edible parts of plants or analogous carbohydrates that
are resistant to digestion and absorption in the human small intestine
with complete or partial fermentation in the large intestine. Dietary fiber
includes polysaccharides, oligosaccharides, lignin and associated plant
substances. Dietary fibers promote beneficial physiological effects includ-
ing laxation and/or blood cholesterol attenuation and/or blood glucose
attenuation (AACC, 2001).
In 2006, FAO/WHO commissioned experts to further consider the
definition of dietary fibre. They recommended that the definition be restricted
to ''dietary fibre consists of intrinsic plant cell wall polysaccharides'', thus
restricting the previous all-encompassing physiological definition. This
recommendation was considered in late 2007 (IFST, 2007). What does this
all mean for the analysis of galacto-oligosaccharides?
