Chemistry Reference
In-Depth Information
product. For example, Oligomate 50 produced by the Yakult Company con-
tains 50-52% galacto-oligosaccharides, 10-13% lactose and 36-39% monosac-
charides (Matsumoto et al., 1993). Purified products are available from many
manufacturers, but costs increase considerably because of the extra processing
steps required. Purified products usually contain between 85 and 99% galacto-
oligosaccharides. It is obvious that there are important differences in the
properties and actions of food-grade oligosaccharide mixtures depending on
the mixture purchased. The applications of oligosaccharides as components in
foods will therefore vary considerably.
General properties of oligosaccharides are listed in Table 5.12. The data
provided by producers, not all of which have been possible to reproduce in
this review, usually include the following factors: sweetness (relative to
sucrose), viscosity, water activity, moisture retention, osmotic pressure, freez-
ing point depression, heat stability, storage stability at different pH values
and colouring by heat.
Most producers also provide safety and toxicological data for acute,
sub-acute and chronic toxicity. Data are also commonly provided to
demonstrate changes in colonic microbial flora following ingestion of oli-
gosaccharides. Usually, substantial increases in bifidobacteria are demon-
strated relative to the other bacterial classes measured.
The physico-chemical properties of oligosaccharides are largely depen-
dent on the molecular weight of the particular oligosaccharide product. These
effects are shown in Table 5.13.
Table 5.12.
General properties of galacto-oligosaccharides
Appearance: translucent / colourless
Sweetness: typically 0.3-0.6 times that of sucrose.
Calorific value: lower than sucrose
Water activity: similar to that of sucrose
Viscosity: similar to that of high-fructose glucose syrup
Heat stability: stable to 1608C for 10 min at pH7 and to 1008C for 10 min at pH 2. More heat
stable than fructo-oligosaccharides at low pH over the range 5-378C
Acid stability: stable to pH 2
Indigestibility: resistant to salivary and pancreatic
-amylase and other carbohydrases, and
gastric juice. Thus, reduce the glycaemic index of foods
Energy Value: about 50% of that of sucrose
Freezing point: reduces the freezing point of foods
Bacteriostatic properties: through competition for mucosal binding sites and adhesion by
pathogens. Some oligosaccharides are also able to absorb lectin-like toxins, e.g., VTEC, ETEC
Bifidogenic ability: able to increase the population of most species of bifidobacteria in mixed
populations of bacteria in both in vitro and in vivo studies in humans and animals
Cariogenicity: acts as an anti-caries agent (anti-cariogenic).
