Natural low-calorie sweeteners - Natural Food Additives, Ingredients and Flavourings - page 66

Regulatory status
Brazzein has no regulatory status at the time of writing. There is no record of a
GRAS notice being submitted to the FDA.

3.5 Other sweeteners
The following sweeteners are included for completeness but are unlikely to be of
great commercial interest.

3.5.1 Curculin and neoculin
Curculigo latifolia Dryand grows in a limited area of western Malaysia and its
fruit contains a unique sweet protein that has both sweet-tasting and taste-
modifying activities. Originally described as a polypeptide homodimer comprising
two identical subunits, curculin was fi rst reported in 1990 (Yamashita et al. 1990).
It is now known that the protein has two different subunits and that this structure
is necessary for its sweetness: laboratory-made homodimers are not sweet. The
active protein has been renamed neoculin (Shimizu-Ibuka et al. 2007) and whole
fruit contain 1-3 mg (Okubo et al. 2008).
Neoculin has a sweet taste that lasts several minutes. Subsequent intake of
water or acid solutions produces a renewed sweetness. Unusually, a concentration-
response curve is available for neoculin, although derived from only four tasters
(Yamashita et al. 1995). It shows a potency of about 2500 at 5% SE and pH 6.
Quite apart from the diffi culty of controlling sweetness that the dual function
of neoculin poses for food formulators, the protein is not heat stable. Incubation
for one hour at temperatures above 50°C in pH 6 buffer caused reduction in
sweetness-inducing ability and complete loss of this property at 75°C; the stability
was the same over the range pH 3-11 (Yamashita et al. 1995). Consequently, it is
largely unsuitable for commercial use as it would not withstand pasteurisation.
The protein has no legal status in the EU or US, and reports that it is included
in the Japanese approved 'List of Existing Food Additives' are not supported
by the list published on the Ministry of Health, Labour and Welfare website
( www.mhlw.go.jp/english/topics/foodsafety/foodadditives/index.html ).

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3.5.2 Lysozymes
The lysozymes from hen, turkey, quail, guinea-fowl and duck eggs as well as the
eggs of the soft-shelled turtle are all reported to be sweet (Maehashi and Udaka
1998; Masuda et al. 2001). However, these proteins are low in potency, ranging
from 10-20 times as sweet as sugar on a weight basis at threshold concentrations
and, therefore, likely to have even lower potency at any concentration approaching
a useful level of sweetness. They have no commercial application as sweeteners,
but are of interest in that they are the only group of naturally sweet molecules not
originating in plants.