Note: Descriptions are shown in the official language in which they were submitted.
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Non-Hazing, Low D.E. Starch Conversion Syrups
round of th_ Invention
The prescnt invention relates to a process for the
production of non-hazing starch conversion syrups having
very low D.E. values. The term D.E. represents Dextrose
Equivalent and refers to the reducing value of dissolved
solids in a starch hydrolyzate expressed as percentage
dextrose.
There is a large market for starch conversion syrups
with bland taste and low sweetness at low D.E. value.
Such syrups are useful as basis for the preparation of
food items as well as bodying agents and as additives
having non-sweet: characteristics. As conversion o starch
to syrups proceeds with lncreasing ~.E. values, the
average molecular weight decreases and at the same time
the solids leve], which is the ability of the syrup to
contribute mouth appeal, chewiness and body decreases.
In many commercial applications, it is desirable to
utilize a non-sweet starch conversion syrup which exhibits
extreme clarity and which will not develop haze on stand-
ing. While such non-hazing characteristics were readily
imparted to starch conversion syrups having higher D.E.
values such as above about 20, it has been extremely
difficult to produce low D.E. starch conversion syrups
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having non-hazing properties. Typically, starch conver-
sion syrups having a ~.E. below about 15 were subject to
haze development upon standing.
Attempts have been made to produce starch conversion
syrups having even lower D.E. values which do not haze or
form suspended matter upon standing. One such attempt to
accomplish this is described in U.S. Patent 3,756,853 in
which starch is first hydrolyzed to a D.E. of Erom about
20 to about 40 and thereafter the resulting starch con-
version syrup was subjected to reverse osmosis until theD.E. of the syrup had been reduced to about 5 from about
18.
It is the object of the present invention to produce
by a single acid hydrolysis step a starch conversion syrup
lS having a very low D.E. value and which does not haze or
form suspended matter upon standing.
Summary of the Invention
According to the present invention an acidic starch
feed slurry at a pH of about 2 to about 4 is passed through
a confined tubu]ar preheat zone and heat is transerred to
the slurry whereby it passes through a gelation stage and
forms into a hot free flowing liquid having a temperature
of at least 100C. This hot liquid is immediately forced
through a restrictive opening and into a conined tuhular
reaction zone ac:companied by a su~den decrease in pressure
whereby the starch is made highly susceptible to cleavage.
This starch liquid is continuously moved under mild hydro-
lyzing conditions through the tubular reaction zone to
cause cleavage of linkages in the starch molecule to form
relatively large molecular polysaccharides, but little or
no mono and disaccharides whereby a non-hazing fluid
starch product is obtained having a n.E. of less than
about 20, preferably less than 5. It is even possible to
obtain non-hazing fluid starch products having D.E. values
of less than 1 and approaching 0, using the process of
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this invention.
The initial starch which is subjected to hydrolysis
may be derived ~rom a wide variety of starch materials,
e.g. corn, potato, tapioca, sago, rice, wheat, waxy maize,
sorghum, etc. The starch may be used in refined form or
as a natural component in cereal grains. To prepare a
feedstock for the hydrolysis stage, the starch is formed
into an aqueous slurry, having a solids content of less
than about 50% by weight and preferably about 25 to 40%.
The pH of the starch slurry is adjusted to a mildly
acidic range of about 2 to 4 by the addition of an acid,
preferably hydrochloric acid. This mildly acidic starch
slurry is then subjected to hydrolysis according to the
above technique.
It is an important feature of this invention that
formation of mono- and disaccharides be substantially
avoided. This is accomplished by careful control of
acidity, forcing the hot free flowing starch liquid
through the restrictive opening before any D.E. value
has been developed and then moving the hot starch liquid
through the tubular reaction zone under mild hydrolysis
conditions sufficient only to cause cleavage of linkages
in the starch molecule to form relatively large molecular
polysaccharides. The most lmportant condition ~or con-
trol of the D.E. value i5 acidity and, ~or instance, ata suitable pH the residence time in the tubular reaction
zone can vary quite widely without affecting D.E. The
residence time in the tubular reaction zone does, however,
affect the nature of the polysaccarides eormed. Typical
residence times in the tubular reaction zone are less
than ~ minutes, with total residence times in both the
preheater and reaction zone being generally less than 10
minute~.
The temperature of the material passing through the
restrictive opening must be above 100C and is usually
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below 170C. The pressure on the inlet side to the
restrictive opening is usually at least 300 psi, with a
pressure drop of at least 100 psi across the restrictive
opening.
The products obtained from the hydrolysis of this
invention are starch conversion syrups of very low ~.E.
values, other~Jise known as malto-dextrins, which exhi-
bit excellent clarity and which do not develop haze upon
standing. This has been achieved with syrups having D.E.
values of less than 1. Refining of the syrups can be
carried out by conventional refining methods, such as
treating with carbon, ion-exchange resins, filtration,
centrifugation and the like.
Description of the Preferred Embodiments
A preferred embodiment oE the reactor for carrying
out this invention is described in the attached Figure 1.
As will be seen from Fig. 1, a holding tank 10 is pro-
vided for a starch slurry feed. This tank has an outlet
line 11 which feeds into a Moyno pump 12. The slurry is
pumped out of pump 12 to line 13 at high pressure and into
a heating coil 14. The pressure within coil 14 is control-
led by varying the speed of pump 12.
The main reactor of this apparatus is a closed and
insulated vessel 15 which is essentially a steam vessel
being supplied by a steam inlet line 16 and a steam out-
let line 17. A steam control valve 30 is pr~vided in the
steam inlet line.
The tube 14 is made of stainless steel and is preEer-
ably arranged as a coil. This is the preheater for the
reaction and the slurry passing through tube 14 passes
through a gel stage and forms into a hot free flowing
liquid. The outlet of preheat tube 14 feeds into a first
restrictive opening or oriice 18 having a much smaller
diameter than the diameter of tube 14. The outlet of the
orifice 18 connects to a further stainless steel tube 19
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which forms the tubular reaction zone of the invention.
This tube in the form of a coil passes back through the
steam vessel 15 and the reaction occurs during the travel
of the hot liquid through coil 19.
In order to control the pressure within coil 19, a
second restrictive opening or orifice 20 is provided at
the outlet. The reaction product is then collected
through outlet line 21.
The following examples are further illustrative em-
bodiments of this invention. All parts and proportions
are by weight unless otherwise specified.
Example 1
(a) The process was carried out using a reactor of the
type described in Fig. 1. The coils 14 and 19 were made
from 1" O.D. stainless 3teel tubing with coil 14 having
a length of 80 feet and coil 19 having a length of 200
feet. The first orifice had a diameter of 0.062 inch and
the second orifice was in the form of a pair of adjacent
openings, each having a diameter of 0.062 inch.
A starch slurry was formed from corn starch and water,
this slurry containing 38% by weight of starch solids.
Hydrochloric acid was added to samples of the slurry to
provide feedstocks of different acid levels.
These feedstocks were passed through the above reactor
under the following conditions:
pH of Temp. at Inlet ~ess. Outlet press. Flow Rate Total D.E.
Slurry 1st. Orifice 1st. Ori~ice 1st. Orifice (G.P.M.) Time
(C) (psi) ~si) (Sec)
2~55 150 850 150 0.94 550 3.5
2.50 147 800 120 0.94 550 7.3
2.45 148 800 110 0.95 538 10.0
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Example 2
A series of further tests were carried out on the same
reactor as used in Example 1, using a slurry of waxy maize
starch as feedstock. Again the slurry contained 38% by
weight of starch solids and hydrochloric acid was added to
samples of the slurry to provide feedstocks of different
acid levels.
These feedstocks were passed through the above reactor
under the following conditions:
pH of Temp. at Inlet press. Outlet press. Flow Rate Total D.E
Slurry 1st. Orifice lst~ Orifice ]st. Orifice (G.P.M.) Time
(C) (psi) ~si) (Sec)
3.4 131 900 130 0.57 905 0.2
3.1 128 900 120 0.73 706 1.6
2.7 120 880 120 0.99 518 3.2
2.6 115 800 150 1.15 450 8.1
2.6 117 800 130 1.01 513 3.3
2.6 118 800 145 1.03 500 8.0
'
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Examele 3
Malto-dextrins were produced using the same general
type of reactor as in Example 1, but with only a single
orifice at the tail end. The single orifice had a dia-
meter of 0.101 inch.
The starch slurry was formed from corn starch and
water and contained 39% by weight of starch solids. The
acid was 30% HCl.
The p~ of the slurry and the D.E. values obtained
were as follows:
Slurry pH D.E.
2.35 17.5
2.8 10.0
3.5 3.0
The three products obtained were spray dried into a
white powder. When dissolved in water, these powders
exhibited similar solubility and clarity properties
commercial enzymatically produced malto-dextrins.
