Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1
This invention relates to a new stable amylaceous
product and to a process for its production.
All starches, except for waxy types, contain two
polymers of glucose, namely amylose and amylopectin.
When a non-waxy starch suspension is heat-treated, the
starch granule obtained swells irreversibly and the
amylose is preferentially solubilized. During cooling
of the suspension, the amylaceous polysaccharides
undergo retrogradation, rapidly in the case of amylose
(i.e. in a few hours) and more slowly in the case of
amylopectin (over a few days). This retrogradation par-
ticularly affects the texture of foods containing these
starches and makes them unacceptable.
Accordingly, it is preferable to use an amylace
ous product rich in amylopectin, such as a waxy corn
starch. However, the stability of the gels and binders
obtained from amylaceous products rich in amylopectin is
not sufficient for the needs of the food industry where
a keeping time of several months is occasionally neces
2o sary.
It is known that inter alia the stability of the
gels thus obtained in storage can be improved, for
example, by treating the amylaceous product to be used
in such a way that the amylopectin molecule is chemical-
ly modified. For example, a few glucose units may be
replaced by hydrophilic or hydrophobic organic molecules
or by a mineral anion which enables the amylopectin
molecule to be stabilized and the risk of retrogradation
to be reduced.
It is also possible to form organic or mineral
diester bridges or diethers between two glucose units
belonging to two different chains. This crosslinking
209f~2~8
enables the swelling which the starch granule undergoes
during the heat treatment to be reduced and hence the
rheological characteristics of the amylopectin molecule
to be modified, making it more resistant to the mechani-
cal treatments (shearing) and to the acidic medium.
These chemical modifications provide the amylopectin
gels obtained with various desirable physical proper-
ties, such as high gelling power and high stability in
neutral and/or acidic medium, for example during cook-
ing, sterilization or deep-freezing treatments. How-
ever, the stable amylaceous products obtained have the
disadvantage of having been chemically treated which may
not be well received by consumers.
The problem addressed by the present invention
was to obviate the disadvantage mentioned above by
providing a process for the production of a stable
amylaceous product involving only a controlled hydroly
sis reaction, but no chemical treatment as such.
Accordingly, the present invention relates to a
process in which a native waxy amylaceous product is
gelatinized and then hydrolyzed with a pure f3-amylase.
The present invention also relates to the stable
native waxy amylaceous product obtained by this process.
One advantage of the invention is that it pro
vides a process which is simple and easy to carry out on
an industrial scale and which gives a stable product in
the form of a gel. In the context of the invention, a
stable product is understood to be a product which,
above all, is stable during storage, i.e. does not
undergo any syneresis or change in viscosity as a
function of time, but which is also stable to freezing/
defrosting. Another advantage of the process according
to the invention is that it gives an end product which
may be used, for example, as a so-called instant binder
in refrigerated or deep-frozen products.
2~09"~2~~
3
In the context of the invention, a waxy amylace-
ous product is understood to be a flour or a starch of
an amylaceous product or of a mixture of amylaceous
products, such as cereals, which are particularly rich
in amylopectin, i.e. contain at least 95% by weight
thereof, based on the total dry weight of starch.
Examples of waxy amylaceous products particularly
corresponding to the invention are waxy cornstarch or
flour, waxy rice starch or flour and waxy barley starch
or flour. A native amylaceous product is understood to
be a product which has not been chemically modified.
In a first step of the process according to the
invention, the amylaceous product is gelatinized. The
gelatinization step may be carried out, for example, by
heat treatment of an aqueous suspension containing 5 to
30% by weight of the amylaceous product for 8 to 12
minutes at a temperature of 65 to 75°C. During this
step, the starch granules swell to allow subsequent
enzymatic hydrolysis. The gelatinized amylaceous
product is then enzymatically hydrolyzed with a pure B-
amylase of vegetable or bacterial origin. To this end,
the 8-amylase may be added in the form of an aqueous
solution in a quantity of 500 to 6000 U per kg starting
starch. The unit U is defined as follows: 1 U corre-
sponds to 1 mg of maltose released in 3 minutes at 20°C/
pH 4.8.
The hydrolysis is preferably carried out over a
period of 5 to 60 minutes at a temperature of 65 to 75°C
and at a pH of 5.6 to obtain a degree of hydrolysis of
at least 5%, as measured by chemical determination of
the reducing sugars (maltose formed). The reaction in
question may also be carried out continuously, for
example by heating the aqueous suspension to a tempera-
ture of 50 to 60 ° C at pH 5 . 6, adding the enzyme, con-
tinuing the heat treatment to a temperature of 65 to
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4
75°C and maintaining that temperature for about 5 to 60
minutes to obtain a degree of hydrolysis of at least 5%.
It has surprisingly been found that a degree of
hydrolysis of only 5% was sufficient to enable a stable
end product to be obtained. The preferred degree of
hydrolysis is of the order of 7 to 20%. Although it is
possible to go to at least as far as 55%, this does
involve a greater loss of end product and hence a
reduction in yield.
The hydrolysis has to be carried out with a pure
f3-amylase because the presence of a-amylase during the
hydrolysis would result in an undesirable reduction in
the viscosity of the starch paste obtained.
In addition, it has found that hydrolysis with a
B-amylase enables the size of the amylopectin molecules
to be reduced while leaving their branched structure
intact so that the viscosity of the gels subsequently
obtained can be increased for a constant concentration
by weight of amylopectin.
Once the desired degree of hydrolysis has been
reached, the enzyme may be inactivated, for example by
heat treatment for 8 to 12 minutes at a temperature of
80 to 85°C, for example by injection of steam into the
double jacket of the reactor. During this step, it is
possible to observe the final swelling of the starch
granule and the total development of the viscosity of
the end product.
The product thus obtained may then be dried, for
example by passage over cylinders rotating at 1 to 3
revolutions per minute and at a temperature of 130 to
160°C, to obtain a precooked amylaceous product having
a dry matter content of approximately 95 to 98% by
weight. The drying step may also be carried out by
spray drying.
The hydrolyzed product obtained may also be
. . 209'7218
directly used as such, i.e. in moist form, without
having to be subjected to a drying step.
The native waxy amylaceous product thus obtained
has been hydrolyzed to a degree of at least 5% with a
5 pure 8-amylase and is stable to the extent that it is
capable of withstanding several freezing-defrosting
cycles without any reduction in its stability and
without any change in its viscosity. This amylaceous
product may be reconstituted in the cold state and may
be used, for example, in sterilized or deep-frozen
sauces or in sterilized milk-based desserts.
The invention is illustrated in more detail in
the following Examples in which parts and percentages
are by weight.
Example 1
An aqueous suspension containing 40 kg waxy
cornstarch and 335 litres water is prepared and then
heated for about 10 minutes at 70°C to gelatinize the
starch. The pH is adjusted to 5.6 with concentrated
acetic acid. The temperature is lowered to 55°C. 10 g
pure Soya f3-amylase (activity 4040 U/g) diluted in 20
litres water are then added and hydrolysis is left to
take place over a period of about 60 minutes to obtain
a degree of hydrolysis of approximately 13%. When the
degree of hydrolysis is reached, the enzyme is inacti-
vated by heat treatment at 80°C, after which the product
obtained is dried at 180 ° C on cylinders rotating at 8
revolutions per minute. The end product obtained has a
dry matter content of 97.5% and is in the form of
flakes.
A starch paste can be prepared from the product
thus obtained by mixing 50 g of the powder-form product
in 950 ml water at 25°C. The gel obtained has a glu-
tinous texture comparable with that of the fresh waxy
6 ~A9~ 2'~~ -
corn gel.
Measurement of the viscosity of the gel obtained
with a Carrimed*instrument gives the following results.:
- without shearing: 167 mPas
- after heating (70°C) without shearing: 130 mPas '~
- after homogenization (Polytroii): 95 mPas
- after heating (70°C) and homogenization: 82 mPas
Example 2
l0 The object of this Example is to determine the
effect of the degree of hydrolysis on the stability of
the gel obtained and the enthalpy of retrogradation of
the amylopectin. A waxy cornstarch is gelatinized,
hydrolyzed and dried in the same way as described in
Example 1, the degree of hydrolysis being varied.
A starch paste is then prepared by preparation of
a mixture containing 20 g of the amylaceous product
obtained in 980 ml water. The starch paste thus ~pre-
pared is then subjected to 1, 3 or 5 freezing/defrosting
cycles (one cycle consisting of freezing to -40°C for at
least 20 minutes followed by defrosting to ambient
temperature) and the volume of water exuded after
centrifugation of the defrosted paste is determined.
The following results in % water exuded are
obtained:
Number of cycles
Degree of hydrolysis 0 1 3 5
0% 0 4 18 27
4.8% 0 0 0 0
5.8% 0 0 0 0
8.1% 0 0 0 0
9.2% 0 0 0 0
12.6% 0 0 0 0
*Trade-mark
A
It can be seen that the hydrolysis step enables
the product to be stabilized because the product does
not exude water if it has been hydrolyzed, even to a low
degree.
A starch paste is then prepared by mixing 4Q0 g
amylaceous product in 600 ml water. The enthalpy of
retrogradation of the amylopectin is measured after
storage for 18 days at 20°C using a Mettler DSC 30
differential calorimeter.
The following results are obtained:
Degree of hydrolysis (%) 0 4.8 5.8 8.1 9.2 12.6
Enthalpy (J/g) 9.6 7.0 4.5 2.9 2.0 0.8
Accordingly, it can be seen that the hydrolysis
step enables the rate of retrogradation of the product
to be reduced, as reflected in the reduction in enthalpy
in dependence upon the degree of hydrolysis.
Example 3
The object of this Example is to determine the
effect of the degree of hydrolysis on the stability of
the gel obtained and the enthalpy of retrogradation of
the amylopectin. A waxy cornstarch is gelatinized,
hydrolyzed and dried in the same way as described in
Example 1, the degree of hydrolysis being varied.
A starch paste is then prepared by preparation of
a mixture containing 400 g of the amylaceous product
obtained in 600 ml water. The starch paste thus pre-
pared is then subjected to 1, 3 or 5 freezing/defrosting
cycles (one cycle consisting of freezing to -40°C fol-
lowed by defrosting to ambient temperature) and the en-
thalpy of retrogradation of the amylopectin is measured
under the same conditions as in Example 2.
The following results in J/g are obtained:
*Trade-mark
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8
Number of cycles
Degree of hydrolysis 0 1 3 5
0% 0 0 2.4 3.1
1.8% 0 0 0.3 1.0
7.9% 0 0 0.3 0.6
15.8% 0 0 0.4 0.8
36.1% 0 0 0.6 0.7
It can be seen that the hydrolysis step enables
the product to be stabilized because the enthalpy of
retrogradation becomes very low, even after several
freezing/defrosting cycles.
Example 4
An aqueous suspension containing 290 g waxy rice
flour and 1650 ml water is prepared and heated for about
10 minutes to 70°C to gelatinize the starch. The pH is
adjusted to 5.6 by addition of concentrated acetic acid.
The temperature is then lowered to 55°C.
0.05 g pure soya 13-amylase (activity 4040 U/g
enzyme) is then added and hydrolysis is left to take
place for about 60 minutes to obtain a degree of hydro-
lysis of 10%. When the degree of hydrolysis is reached,
the enzyme is inactivated by heating to 80°C and the
starch paste obtained is dried. The end product ob-
tained has a dry matter content of 92% and is present in
powder form.
A starch paste may be prepared by mixing 20 g of
the product thus obtained with 980 ml water. The starch
paste thus prepared is then subjected to 1, 3 or 5
freezing/defrosting cycles and the volume of water
exuded after centrifugation of the defrosted starch
paste is determined.
The following results in % water exuded are
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obtained:
Number of cycles
Degree of hydrolysis 0 1 3 5
0% 61 58 56 49
9.8% 0 0 0 0
Accordingly, a product according to the invention
can also be prepared from a waxy rice.
Example 5
This Example illustrates the continuous appli-
cation of the process according to the invention.
An aqueous suspension containing 50 kg waxy
cornstarch, 230 litres water and 24.5 g pure soya f3-
amylase is prepared and heated to 70°C by injection of
steam. Hydrolysis is then left to take place for about
60 minutes at 70°C to obtain a degree of hydrolysis of
7%. When this degree of hydrolysis is reached, the
enzyme is inactivated by heating to 80°C. The product
obtained has a dry matter content of 18% and may be
directly used. The product obtained may also be dried
at 180°C on cylinders rotating at 8 revolutions per
minute to obtain an end product in the form of flakes
having a dry matter content of 95%.
Example 6
This Example illustrates the use of the product
according to the invention in a more complete recipe.
A tomato sauce is prepared from tomato concen-
trate, cream containing 35% fats, spices, salt and
approx. 5% of the amylaceous product according to the
invention, the amylaceous product having been prepared
from cornstarch, hydrolyzed in accordance with the
to
invention and having a degree of hydrolysis of 8.1%. A
sauce containing an amylaceous product based on corn-
starch which has not been hydrolyzed is prepared for
comparison. The sauces thus prepared are cooked for 10
minutes, placed in a bag, frozen and kept in a refriger-
ator for 1 week at -18°C. Thereafter, the sauces are
heated on a water bath to approximately 60°C.
The following results are obtained:
Sauce according to the invention:
stable to freezing/defrosting (no water exuded)
smooth and creamy appearance
Comparison sauce:
. unstable to freezing/defrosting (water exuded)
contains lumps.
It can be seen that the sauce prepared with the
amylaceous product according to the invention is stable
in contrast to the comparison sauce.
