Natural low-calorie sweeteners - Natural Food Additives, Ingredients and Flavourings - page 57

Metabolism
When ingested, glycyrrhizin itself is not well absorbed. Bacteria in the digestive
tract break it down to the aglycone, glycyrrhetic acid, which is rapidly absorbed
and has pharmacological actions. For example glycyrrhizinates inhibit
11 β -hydroxysteroid dehydrogenase, the enzyme responsible for inactivating
cortisol. As a result, the continuous, high-level exposure to glycyrrhizin
compounds can produce hypermineralocorticoid-like effects in both animals
and humans. These effects, also known as 'pseudohyperaldosteronism', are
reversible upon withdrawal of liquorice or glycyrrhizin. Other in vivo and clinical
studies have reported benefi cial effects of both liquorice and glycyrrhizin
consumption including anti-ulcer, anti-viral and hepatoprotective responses.
Isbrucker and Burdock (2006) provide a comprehensive review of glycyrrhizin
absorption, distribution, metabolism and elimination as well as its biochemical
effects.
Glycyrrhizin, although widely employed, is used in such small quantities
that any energy it contributes is negligible. US consumption, for example, has
been estimated at up to 3.6 mg/kg bodyweight (bw) per day (Isbrucker and
Burdock 2006).

Sensory properties
The onset of glycyrrhizin's sweetness is very slow. It increases very gradually to
a maximum and then has a pronounced linger (DuBois 2007). Its marked liquorice
taste limits its use as a sweetener.
There are only meagre data on the concentration-response of glycyrrhizin. The
fi gure of 50 is often given for its potency, but various fi gures appear in the
literature, such as 50-100 (Kinghorn and Compadre 2001) and 93-170 (Kinghorn
and Kim 2006), but it is unclear if the free acid or a salt is meant or, indeed, if
these are pure compounds or commercially standardised extracts containing
diluents. Other work is consistent with a potency of 200 at 5% SE for glycyrrhizic
acid (Mizutani 2007), which seems optimistic at that degree of sweetness. In
contrast, the concentration-response curve shown in Fig. 3.9, from the reliable
study by DuBois et al. (1991), indicates a potency of 110 at 5% SE for ammonium
glycyrrhizinate.

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Applications
The main applications of glycyrrhizin are for fl avouring tobacco products and
liquorice confectionery. Other uses include as a foaming agent and fl avour
modifi er in beer, as a fl avour enhancer for cocoa - where it also fi nds use in the
control of chocolate bloom. At low concentrations it is used for fl avour modifi cation
of other HPS and to reduce the bitterness of some pharmaceuticals. Like the
steviol glycosides, it is popular in Japan for ameliorating the burning sensation of
highly salted pickled products. Also in Japan, liquorice is an ingredient in 75% of
herbal medicines.
The paste form of crude extract is favoured for tobacco products - the major
destination in the US, accounting for 90% of US liquorice use (Fenwick et al.