Chemical and Functional Properties of Food Saccharides

© 2004 by CRC Press LLC
high percentages, are also responsible for the positive effects such as stimulating
the intestinal tract and supporting consumers’ well feeling. Carbohydrate profiles
and the spectrums of low- and high-molecular-weight fructans strongly depend on
cultivar, climate, environmental conditions, and harvesting period.
13.4.7 ALLIUM L. SPECIES
Only few of the more than 700 Allium species are utilized in human nutrition. These
include A. cepa L. (onion, shallot), A. ampeloprasum L. var. prooum (leek), A.schoenoprasum
L. (chives), and A. sativum L. (garlic).
Dry matter contents of onion and shallot bulbs (thickened leaves for storage
reserve substances) are 9–14%, with 60–80% aqueous soluble carbohydrates. About
half the soluble carbohydrates are FOSs and fructans, the latter having DPs between
3 and 10. Once again, there are significant differences in the contents of fructose,
glucose, sucrose, and fructans, depending on cultivars, periods of harvesting, and
storage conditions. For instance, concentrations of mono- and disaccharides can be
increased two- or threefold, with a simultaneous decrease or absence of high-DP
fructans, if storage temperature is changed from room temperature to 2˚C (Figure
13.6). Table 13.2 gives the fructan composition of a commercially available freshly
harvested onion with significant amounts of components with DP of 5 or lower.
Dry matter contents of chives and leek are similar to those of onion and shallot,
between 10 and 14%, with aqueous soluble carbohydrates between 60 and 80%.
However, fructan content is significantly higher (80%), and the content of highmolecular-weight
fructans with DPs over 10 is ca. threefold that of onion.
Garlic cultivars differ significantly from onions with respect to their carbohydrate
composition. Dry matter content of freshly harvested garlic bulbs ranges from 32
to 45%, with slight variations depending on cultivar and storage conditions. Fructan
content is ca. 22 to 24% of the fresh weight, ca. sixfold that of onion. Fructan content
in dry matter ranges from 58 to 68%, with only a minor content (1%) of lowmolecular-weight
fructans. Fructose and glucose contents are extremely low (below
1%), and sucrose content ranges from 4 to 7%. Table 13.2 lists the carbohydrate
profile of commercially available garlic.
13.4.8 POACEAE (CEREALS, GRASSES)
Members of the family Poaceae, in particular, seeds of the cereals wheat (Triticum
aestivum L.), rye (Secale cereale L.), oat (Avena sativa L.), and barley (Hordeum
vulgare L.), play an important role in human nutrition (Table 13.2). In the growth
period of roots, leaves, and stems, grasses utilize fructans as storage metabolites,
which are later found as costorage polysaccharides with glucans in the seeds (caryopses).
In early development stages, the caryopses contain a dry matter fructan
content of 2 to 4%. In adult seeds of wheat grains, this content is reduced to ca. 1.3
to 2.5%. After milling, the fructan content in flour ranges from 1.0 to 1.3%, and in
the bran is ca. 3%.
Adult rye grains contain 4–6% fructans, with 2.5–4% in the flour and 7% in the
shorts after milling. 34 Barley grains contain 0.5 to 1.5% and oat grains ca. 0.5%