Natural low-calorie sweeteners - Natural Food Additives, Ingredients and Flavourings - page 50

Fig. 3.4 Stability of rebaudioside A under different conditions of temperature and pH.

liver, and excrete that in the urine. Because of this common metabolic route, the
ADI of the glycosides is expressed as an intake of steviol (JECFA ADI 0-4 mg/kg
bw (WHO 2009)). This means that the actual ADI in terms of glycoside is different
for each, depending on its molecular mass. For example, 4 mg steviol are furnished
by 10.11 mg stevioside or by 12.15 mg rebaudioside A.
Although broken down by colon fl ora, the steviol glycosides are not
fermented by oral bacteria and should be non-cariogenic, although specifi c clinical
demonstration of this advantage is currently underway. The glycosides also have
no effect on blood glucose concentration or insulin demand.
A detailed review of the modern view of the metabolism of rebaudioside A is
given by Brusick (2008).

Sensory properties
The individual steviol glycosides exhibit different potencies ranging from about
30 (dulcoside A, rebaudioside C) to 200-300 (rebaudioside A). The concentration-
response curves for room temperature, aqueous stevioside and rebaudioside A are
contrasted in Fig. 3.5 from which it is apparent that the potency of stevioside is
120 and that of rebaudioside A 250, both measured at 5% SE.
The glycosides also differ in the extent to which they have non-sweet, generally
undesirable, side tastes. Rebaudioside A is held to have the least of these
characteristics, often described as bitter and liquorice. Their negative impact tends
to be signifi cant only at high concentrations of rebaudioside A, say >6% SE
(Prakash et al. 2008). In contrast, stevioside is markedly inferior to rebaudioside
A in taste quality.
Rebaudioside A's sweetness has a lasting quality. It is perceived longer than
sucrose or aspartame at roughly similar peak sweetness levels (Prakash et al.
2008).

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