Note: Descriptions are shown in the official language in which they were submitted.
CA 02238925 1998-05-28
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
In one of its aspects, the present invention relates to a salt formulation. In
another
of its aspects, the present invention relates to a process for producing a
salt formulation.
More particularly, in a preferred embodiment, the present invention is
concerned with the
provision of food grade salt formulations.
DESCRIPTION OF THE PRIOR ART
Iodine deficiency causes several serious health problems that can lead to
disabling
and/or retarded development, and to the onset of a variety of diseases. In
developed
countries, it has been known for a number of years to fortify the food grade
salt supply
with iodine. More specifically, this is known to lead to a dramatic
improvement in the
iodine status of the general population. Further, plans are under way to
introduce salt
iodization in many developing countries, under programs initiated by UNICEF,
the
World Health Organization, governments and private initiatives.
Food grade salt is an ideal vehicle for micronutrient distribution, since its
consumption and use is not linked to economic status. Further, per capita
intake within
a society is almost constant. Iodine is normally added in the form of: (i)
potassium iodide
in developed countries, and (ii) potassium iodate in developing countries.
Iodide readily oxidizes in the presence of oxygen or oxidizing agents to
elemental
iodine, which sublimes at a relatively high vapour pressure. This leads to the
rapid loss
of iodine from salt. It is known in the art to mitigate this problem by the
addition of a
reducing agent, such as dextrose, and/or by reducing the moisture content of
the salt
through drying or by a desiccant. If the salt contains impurities which absorb
water from
the air, or which catalyze the oxidation of iodide, the iodine produced
therefrom will
readily evaporate from the moisture. Further, it is known that iron compounds
catalyze
these reactions leading to the loss of iodine. This is especially unfortunate
since salt
would be an ideal carrier for other micronutrients, such as iron.
In developing countries with tropical and subtropical climates, iodine is
added in
the form of iodate, which is an oxidized iodine compound. As is known, iodate
resists
the release and loss of elemental iodine through air. Recent studies on the
stability of
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iodine in salt iodized by potassium iodate indicate that, in the presence of
impurities
typical of local salts in many developing countries, most of the added iodine
is lost within
6-12 months under humid conditions typical of these countries - see Diosady et
al., Food
and Nutrition Bulletin, Dec. 1997 issue, the contents of which are hereby
incorporated
by reference.
Over the past decade there have been many unsuccessful attempts at "double
fortification" of salt with: (i) iron to prevent anemia, and (ii) iodine for
the prevention of
iodine deficiency disorders. The Micronutrient Initiative, created by the
International
Development Research Centre of Canada has been in the forefront of promoting
double
fortification.
Iron is best absorbed in the form of ferrous iron compounds. Unfortunately,
these
are reducing agents, that will readily reduce the potassium iodate added to
salt to
elemental iodine which, as discussed above will then evaporate. This problem
is
compounded by the fact that, during the process, the ferrous iron is oxidized
to the ferric
form resulting in a decrease in the bioavailability of iron.
In light of these deficiencies, it would be desirable to have an improved
fortified
salt formulation.
SUMMARY OF THE INVENTION
It is an object of the present invention to obviate or mitigate at least one
of the
above-mentioned disadvantages of the prior art.
Accordingly, in one of its aspects, the present invention provides an
encapsulated
salt formulation comprising a salt and a nutrient, the nutrient being
encapsulated in a
digestible matrix such that the salt and the nutrient are physically
independent.
In another of its aspects, the present invention provides a process for
producing
an encapsulated salt formulation the process comprising the step of admixing a
salt and
a nutrient, the nutrient being encapsulated in a digestible matrix such that
the salt and the
nutrient are physically independent.
Thus, the present inventor has developed a novel approach for the
fortification of
salt in a salt formulation. Generally, the novel approach relates to
encapsulating at least
one nutrient in a digestible matrix which is then combined with the salt. As
used
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throughout this specification, the term "digestible matrix" is intended to
have a broad
meaning and encompasses any material which is non-reactive with the nutrient
and the
salt but will disintegrate or otherwise breakdown in the digestive tract of
the individual
consuming the salt formulation. Once the nutrient is encompassed by the
digestible
matrix, the latter forms a physical barrier around the nutrient effectively
preventing
contact with the salt and/or other nutrients and/or impurities in the salt.
A particularly preferred embodiment of the present salt formulation is in the
double fortification of salt with (i) iron to prevent anemia, and (ii) iodine
for the
prevention of iodine deficiency disorders. In this preferred embodiment, the
iodine IS
independently encapsulated such that, when converted into a salt formulation,
there is no
physical contact between the salt/iron and iodine, nor is the iodine able to
contact the
atmosphere or moisture in the salt. Thus, iodine loss from the present salt
formulation
is obviated or mitigate, even in the presence of moisture.
As will be illustrated below, this double fortified system has been tested
with a
number of encapsulating agents, and a series of iodine and iron compounds.
Successful
application of this system will make it possible to administer iodine and iron
to high-risk
populations through nutritional means without involvement of the limited
health-care
system in developing countries.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
For the successful administration of iodine, it is preferred that the iodine
be
dispersed homogeneously in the salt. This helps to prevent great variation in
the daily
intake by the consumer. As the daily requirement is only in the order of
150,ug, the
iodine must be very finely dispersed.
As discussed above, in order to protect the iodine from breakdown and release
from the salt formulation, it is important that it be protected from contact
with either
moisture and/or with reactive additives or impurities present in the salt.
The iodine, added either as iodate or iodide, can be encapsulated in a
moisture-
proof, digestible matrix to protect it from breakdown. The encapsulation
technique used
is not particularly restricted and is within the purview of a person skilled
in the art. Thus,
encapsulation may be achieved using one or more of the conventional
techniques: spray
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drying, coating in a fluidized bed, coating in a conventional rotary drum,
coacervation
and the like. Of course, this is merely a non-limiting list of possible
encapsulation
techniques. Those of skill in the art will recognize that the intent is to
achieve
encapsulation and that the precise mode of achieving encapsulation is not
particularly
critical.
It is desirable that the encapsulated particles of encapsulated iodine be
similar in
size to the particles of local salt, as small or large particles would
segragate from the salt
during transport. This could result in very high local concentration of
iodine. Since a
particle of the size of a typical grain of salt weighs up to several thousand
micrograms,
singlegrains of encapsulated potassium iodide or potassium iodate can contain
several
times the recommended daily intake of iodine. Thus, it is preferred that the
iodine
compounds be diluted in the encapsulated particles by a factor of 5-200.
To facilitate safe administration of encapsulated iodine compounds, several
techniques have been developed (illustrated hereinbelow) that enable the
production of
encapsulated particles similar in size to local salts, with an iodine content
in the range of
from about 1% to about 5% by weight.
The preferred encapsulating technique is spray drying. To achieve this,
potassium
iodide or potassium iodate is preferably dissolved in an aqueous system,
together with
an encapsulating agent. The solution may then be spray dried to produce
microcapsules
of a digestible encapsulating agent, in which the iodine compound is
distributed, without
contact with the surrounding air or solution.
The encapsulating agent (which give rise to the digestible matrix) may be any
digestible compound. The preferred agents are readily soluble in warm aqueous
systems,
but exhibit substantially no degradation in the presence of moisture absorbed
from the
air by hygroscopic impurities that may be present in salt. Thus, the
encapsulating agent
may be a moisture resistant, digestible food grade material selected from the
group
comprising a carbohydrates (e.g., a modified starch), a fat (e.g.,
hydrogenated mono-
glycerides, hydrogenated di-glycerides and mixtures thereof), proteins (e.g.,
zein),
inorganic compounds (e.g., sodium hexametaphosphate), a polymeric compound
(e.g.,
natural or artificial polymeric materials, such as shellac). The preferred
encapsulating
agents include dextrins, other modified starches, shellac, zein and mixtures
thereof.
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Iron may also be encapsulated. In the case of ferrous fumarate and
ferrous sulfate, the encapsulation would serve to stabilize these compounds
from slow
oxidation, thus improving bioavailability, improving the colour of fumarate,
and the taste of ferrous sulfate. The encapsulation technques are
conventional.
Embodiments of the present invention will be described with reference to the
following Examples which are provided for illustrative purposes only and
should not be
used to construe or otherwise limit the scope of the present invention.
EXAMPLE 1
Potassium iodide was dissolved in a hot 10% (w/v) aqueous solution of dextrin
with a low dextrose equivalent. The solution was spray dried with an air
temperature of
160 C in a NiroTM pilot scale spray drier. This resulted in the production of
12 kg of fine
powder having a potassium iodide content of 2.1 % by weight.
The encapsulated iodine was added to fine granular salt (Toronto Salt Chemical
Co.) in a ribbon blender, at a ratio which resulted in a final iodine content
of 50,ug/g.
Some of this salt was mixed with ferrous fumarate to a final concentration of
3000,ug
ferrous fumarate per gram of salt. The salt samples were subjected to a series
of stability
tests at high temperature and humidity.
While a comparative salt formulation to which the potassium iodide was added
directly (with or without ferrous fumarate) lost more than 90% of its iodine
content
within 9-12 months, the salt samples produce in this Example (i.e., with
encapsulated
iodide) retained 75-90% of the added iodine after 12 month storage at 40 C
under 100%
humidity.
Laboratory tests with rats, and later human trials confirmed the
bioavailability of
the encapsulated iodide.
EXAMPLE 2
Potassium iodate was dissolved in a hot 10% (w/v) aqueous solution of dextrin
with a low dextrose equivalent. The solution was spray dried with an air
temperature of
160 C in a BuchiTM laboratory scale spray drier. A variety of fine powders,
with
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potassium iodate contents ranging from 0.5% to 2.1% by weight, were produced,
depending on the initial iodide content.
The encapsulated iodine was added to fine granular in a 3 kg laboratory ribbon
blender, at a ratio which resulted in a final iodine content of 50gg/g. Some
of this salt
was mixed with ferrous fumarate to a final concentration of 3000,ug ferrous
fumarate per
gram of salt. The salt samples were submitted to a series of stability tests
at high
temperature and humidity.
While a comparative salt formulation to which the potassium iodide was added
directly (with or without ferrous fumarate) lost more than 90% of its iodine
content
within 9-12 months, the salt samples produce in this Example (i.e., with
encapsulated
iodide) retained 75-90% of the added iodine after 12 month storage at 40 C
under 100%
humidity.
EXAMPLE 3
The methodology in Example 2 was repeated using sodium hexametaphosphate
as the encapsulating agent. A stable formulation was obtained.
EXAMPLE 4
The methodology in Example 3 was repeated using potassium iodide as the iodine
source. A stable formulation was obtained.
EXAMPLE 5
Samples of sodium chloride crystals containing 2-10% potassium iodide were
prepared, by both co-precipitation of the sodium chloride with the iodide.
These crystals
were coated with zein, an alcohol soluble protein, by spraying a solution of
10% zein in
ethanol on to salt suspended in a fluidized bed held at 90 C.
The alcohol evaporated leaving an encapsulated salt sample, stable under the
high
temperature, high humidity storage conditions.
EXAMPLE 6
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The methodology of Example 5 was repeated with 2-10% potassium iodate. A
stable formulation was obtained.
EXAMPLE 7
The methodology of Example 5 was repeated with food grade shellac replacing
the zein as a coating agent. A stable formulation was obtained.
EXAMPLE 8
The methodology of Example 6 was repeated with food grade shellac replacing
the zein as a coating agent. A stable formulation was obtained.
EXAMPLE 9
The methodology of Example 5 was repeated, using a tumble drier instead of a
fluidized bed reactor. A stable formulation was obtained.
EXAMPLE 10
The methodology of Example 6 was repeated, using a tumble drier instead of a
fluidized bed reactor. A stable formulation was obtained.
EXAMPLE 11
The methodology of Example 7 was repeated, using a tumble drier instead of a
fluidized bed reactor. A stable formulation was obtained.
EXAMPLE 12
The methodology of Example 8 was repeated, using a tumble drier instead of a
fluidized bed reactor. A stable formulation was obtained.
EXAMPLE 13
The methodology of Example 9 was repeated, using a molten mixture of mono-
and di-glycerides from hydrogenated soybean oil as the coating agent. The
coating agent
solidified on cooling, resulting in a stable formulation.
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EXAMPLE 14
The methodology of Example 10 was repeated, using a molten mixture of mono-
and di- glycerides from hydrogenated soybean oil as the coating agent. The
coating agent
solidified on cooling, resulting in a stable formulation.
EXAMPLE 15
The methodology of Example 9 was repeated, using salt prepared by coating salt
grains with potassium iodide to a bulk concentration of 3% by weight. A stable
formulation was obtained.
EXAMPLE 16
The methodology of Example 15 was repeated, using salt prepared by coating
salt
grains with potassium iodate to a bulk concentration of 3% by weight. A stable
formulation was obtained.
Thus, as described above, the preferred embodiment of the invention relates to
a
novel stable iodide or iodate containing salt formulations that protects the
salt from loss
of iodine during extended storage under conditions typical of tropical and
subtropical
countries. The stability of the system is not influenced by typical salt
impurities, or added
micronutrients such as the ferrous or ferric compounds.
While this invention has been described with reference to illustrative
exemplary
embodiments, the description is not intended to be construed in a limiting
sense. Various
modifications of the illustrative embodiments, as well as other embodiments of
the
invention, will be apparent to persons skilled in the art upon reference to
this description.
It is therefore contemplated that the appended claims will cover any such
modifications
or embodiments.
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