Title: Alternative Sweeteners

Stevioside 171
been determined as follows: rebaudioside A, 250–450; rebaudioside B, 300–350;
rebaudioside C, 50–120; rebaudioside D, 250–400; rebaudioside E, 150–300;
dulcoside A, 50–120; and steviolbioside, 100–125 (2). Rebaudioside A, the second
most abundant ent-kaurene glycoside occurring in the leaves of S. rebaudiana
is better suited than stevioside for use in foods and beverages because it is not
only more water soluble but it also exhibits a pleasanter taste (2, 4).
Many attempts have been made to improve the sweetness hedonic parameters
of stevioside by formulation with a variety of flavor-masking and sweetnessenhancing
agents (1, 2). Efforts have been made to produce strains of S. rebaudiana
that have a higher ratio of rebaudioside A to stevioside compared with wild
Paraguayan populations to harness the preferential properties of rebaudioside A
compared with stevioside (2). In another type of strategy, enzymatic transglycosylation
of stevioside has led to analogs with improved taste profiles over the
parent substance (2, 4). In this procedure, modification of the sugar moiety at C-19
of stevioside is conducted with enzymic transglycosylation, and cyclomaltodextringlycanotransferase
(CGTase) is used to catalyze trans-α-1,4-glycosylation (4).
A transglycosylated (‘‘sugar-transferred’’) product of stevioside is sold commercially
in Japan, produced by shortening the α-glucosyl chain of the mixture of
compounds obtained by CGTase treatment using β-amylase (4).
IV. AVAILABILITY AND COST
It is apparent that the natural area of distribution of S. rebaudiana has been considerably
reduced in recent years in its native habitat in the Sierra of Amambay in
northeastern Paraguay, where the plant is found in natural grasslands on mountain
slopes and valleys occurring at altitudes of 500–700 m above sea level. The
reason for this is that many of the subtropical forests surrounding the natural
populations of S. rebaudiana have been exploited for their timber, with the newly
cleared land then used for other agricultural purposes. In addition, thousands of
S. rebaudiana plants have been transplanted to other areas to start large-scale
plantations. Because S. rebaudiana is sensitive to changes in its environment,
the net effect is that the germplasm of this species may be threatened at present
(2).
As noted earlier in this chapter, by far the largest cultivation areas where
S. rebaudiana is currently produced are in the People’s Republic of China. The
price of S. rebaudiana products has become much cheaper in recent years. For
example, sweet products made from S. rebaudiana leaves containing high levels
of stevioside were initially priced at 100,000 Japanese yen (equivalent to $833
U.S. at 120 yen per $) but have been reduced to less than 10,000 Japanese yen
(equivalent to $8.33 U.S.) (11).