INTERNATIONAL PROGRAMME ON CHEMICAL SAFETY
WORLD HEALTH ORGANIZATION
TOXICOLOGICAL EVALUATION OF SOME
FOOD COLOURS, EMULSIFIERS, STABILIZERS,
ANTI-CAKING AGENTS AND CERTAIN
OTHER SUBSTANCES
FAO Nutrition Meetings Report Series
No. 46A WHO/FOOD ADD/70.36
The content of this document is the result of the deliberations of the
Joint FAO/WHO Expert Committee on Food Additives which met in Rome,
27 May - 4 June 19691
Food and Agriculture Organization of the United Nations
World Health Organization
1 Thirteenth report of the Joint FAO/WHO Expert Committee on Food
Additives, FAO Nutrition Meetings Report Series, in press;
Wld Hlth Org. techn. Rep. Ser., in press.
AMYLOSE AND AMYLOPECTIN
Biological Data
Normal native starches consist of a mixture of 15-30 per cent. amylose
and 70-85 per cent. amylopectin. Amylose structurally is a linear
polymer of anhydroglucose units, of molecular weight approximately
between 40 000 and 340 000, the chains containing 250 to 2000
anhydroglucose units. Amylopectin is considered to be composed of
anhydroglucose chains with many branch points; the molecular weight
may reach as high as 80 000 000.
One hundred per cent. amylopectin or "waxy" starches are commercially
available having been extracted from special mutants of the parent
plant e.g. waxy corn or waxy rice. Starches with a very high amylose
content have also been produced, but on a limited scale for special
application. The granules of native starches are extracted from the
plant source by purely physical means, washed and dried. Even in this
way a certain small amount of modification takes place so that the raw
starch is strictly speaking not the same as it existed in the plant.
The changes which have taken place are, however, only of academic
interest. From the nutritional point of view it is important to
realize that the human gastro-intestinal tract digests very
efficiently raw cereal and root starches such as wheat, maize, rice
and cassava but is not able to digest easily raw potato, arrowroot and
canna starches (Booher et al., 1951).
Digestibility of starches may be assessed by studying the action of
pancreatin or other sources of amylase (Leach & Schoch, 1961)
(Sandstedt et al., 1962) or of taka-diastase (Kihara & Kawase, 1949)
in vitro on the raw granular starch, or by feeding the raw starch to
animals such as rats and chicks. But from the standpoint of use in the
human diet it is the gelatinized (cooked) form that requires
evaluation. From the work of Sandstedt et al. (1962) and Borchers
(1962) it is clear that both in vitro studies and animal feeding
establish the resistant character of some high amylose corn starches
to amylolytic attack.
Nevertheless it does not appear likely that in practice high amylose
corn starches in gelatinized form will present any problem of
digestibility to man, who has no difficulty with gelatinized potato
starch. The digestibility of raw granular potato starch in vitro was
15.98 per cent. under conditions where corn starch yielded a value of
65.64 per cent. (Kihara & Kawase, 1949). In the studies by Sandstedt
et al. (1962) the susceptibility of potato starch in vitro to
pancreatic digestion was far lower than that of the most resistant
high-amylose corn starch. Although in vivo digestibility invariably
exceeds the in vitro value, it is unlikely that potato starch would
prove more digestible than high-amylose corn starch, either raw or
gelatinized.
Comments
These native starches should be regarded as food rather than food
additives.
EVALUATION
Not limited except for good manufacturing practice.
REFERENCES
Booher, L. E., Behan, I., & McMeans, E. (1951) J. Nutr., 45, 75
Borchers, R. (1962) Cereal Chem., 39, 145
Kihara, Y. & Kawase, Z. (1949) Rept. Food Res. Inst. (Japan), 2,
25
Leach, H. W. & Schoch, T. J. (1961) Cereal Chem., 38, 34
Sandstedt, R. M. et al. (1962) Cereal Chem., 39, 123