CA1107727A - Continuous production of starch hydrolysates - Google Patents
Continuous production of starch hydrolysatesInfo
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- CA1107727A CA1107727A CA294,943A CA294943A CA1107727A CA 1107727 A CA1107727 A CA 1107727A CA 294943 A CA294943 A CA 294943A CA 1107727 A CA1107727 A CA 1107727A
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- Prior art keywords
- starch
- zone
- process according
- orifice
- elevated pressure
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- C—CHEMISTRY; METALLURGY
- C13—SUGAR INDUSTRY
- C13K—SACCHARIDES OBTAINED FROM NATURAL SOURCES OR BY HYDROLYSIS OF NATURALLY OCCURRING DISACCHARIDES, OLIGOSACCHARIDES OR POLYSACCHARIDES
- C13K1/00—Glucose; Glucose-containing syrups
- C13K1/06—Glucose; Glucose-containing syrups obtained by saccharification of starch or raw materials containing starch
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- Health & Medical Sciences (AREA)
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- General Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Biochemistry (AREA)
- Organic Chemistry (AREA)
- Polysaccharides And Polysaccharide Derivatives (AREA)
Abstract
CONTINUOUS PRODUCTION OF STARCH HYDROLYSATES
Abstract of the disclosure A process for producing starch hydrolysates which comprises continuously moving an aqueous acidic starch slurry through a tubular heating zone at a pressure substantially above that of saturated steam to raise the:
temperature of the slurry to at least 100°C., thereby causing the starch slurry to at least partially gelatinize and thereafter form into a hot starch liquid, characterized in that the hot starch liquid from the tubular heating zone at a first elevated pressure is forced through a restricting zone and into a tubular reaction zone having a second elevated pressure substantially below said first elevated pressure whereby a highly reactive starch liquid emerges from the restricting zone into the tubular reaction zone in the form of a fine spray or mist with a sudden release of energy and continuously moving the highly reactive starch liquid through the tubular reaction zone to form a homogeneous starch hydrolysate.
Abstract of the disclosure A process for producing starch hydrolysates which comprises continuously moving an aqueous acidic starch slurry through a tubular heating zone at a pressure substantially above that of saturated steam to raise the:
temperature of the slurry to at least 100°C., thereby causing the starch slurry to at least partially gelatinize and thereafter form into a hot starch liquid, characterized in that the hot starch liquid from the tubular heating zone at a first elevated pressure is forced through a restricting zone and into a tubular reaction zone having a second elevated pressure substantially below said first elevated pressure whereby a highly reactive starch liquid emerges from the restricting zone into the tubular reaction zone in the form of a fine spray or mist with a sudden release of energy and continuously moving the highly reactive starch liquid through the tubular reaction zone to form a homogeneous starch hydrolysate.
Description
il~77;27 This invention relates to the conversion of poly-saccharide materials, such as starch, in the production of dextrose-containing products. For convenience , the description of the invention is hereinafter limited to starch, but it will be understood that it is also ap-plicable to other dextrose polymers.
The process adopted in most existing plants for the conversion of starch is a batch process involving hydrolysis with dilute acid. In recent years, various forms of continuous processes have been developed such as that described in Kroyer, U.S. Patent 2,735,792, issued February 21, 1956. A problem with all of these systems has been tha~ of achieving uniform hydrolyzation. Also, whether a batch process or one of the known continuous processes is used, the maximum dextrose e~uivalent (D.E.) which can be reached during acid hydrolysis is about 50.
Attempts to produce D.E. values above 50by acid hydrolysis result in an unsatisfactory product.
Because of this problem, enzymes are now widely used for starch hydrolysis. Thus, it is commonplace to carry out an initial acid hydrolysis to a D.E. value of 50 or less and then continue with one or more enzyme conversions to produce higher ~.E. values. It is also known to use enzymes both for liquification and sacchari-fication.
Enzymes have also not been the full answer to the problems of starch hydrolyzation in that they are unable to act on retrogradation products and many of the enzymes capable of hydrolyzing the glucosidic linkages in the starch molecules are unable to hydrolyze all of the 1,4 and 1,6 bonds. Moxeover, various other enzyme systems may synthesize appreciable amounts of di- or trisaccharides from dextrose or maltose, thereby pre-venting complete hydrolysis to dextrose. It is bel-ieved that these 2roblems are further compounded by the fact that the starch molecules have a curled or spiral configuration which interferes with any access by the enzymes to the reactive points where hydrolysis would ~ormally occur.
It is the object of the present invention to provide an improved process for the hydrolysis of polysaccharides, such as starch.
Thus, the present invention in its broadest aspect relates to a process for the conversion of poly-saccharide materials, such as starch, into dextrose-containing products, which comprises continuously moving an aqueous acidic polysaccharide slurry through a tubular heating zone at a pressure substantially above that of saturated steam to raise the temperature of the slurry to at least 100C., thereby causing the starch slurry to at least partially gelatinize and thereafter form into a hot starch liquid. According to the inventivP feature, the hot starch liquid from the tubular heating zone is at a first elevated pressure of at least 20 ~g/sq. cm. forced throu~h a restricting zone having a cross-sectional area less than 25~ of the cross-sectional area of the tubular heating zone and into a tubular reaction zone having a second elevated pressure substantially below that of the first elevated pressure whereby a highly reactive starch liquid emerges from the restricting zone into the tubular reaction zone in the form of a fine spray or mist with a sudden release of energy. This highly reactive starch liquid is . , ; ~.~r ~' 1~77Z7 continuously moved through the tubular reaction zone to form a homogenous dextrose-containing product.
The restricting zone is preferably in the form of a restricting orifice having a cross-sectional area significantly smal]er than that of the tubular heating, zone, e.g. less than 25% of the cross-sectional area of the tubular heating zone. It has also been found ad-vantageous for the orifice to have substantial length relative to its cross-sectional area, e.g. a length:
diameter ratlo of at least 4:1, although a ratio as small as 1:1 can be used.
The hot starch liquid entering the restricting _ _ _ _ _ . . ... ..
zone will normally have a pressure of at least 20 kg/sq. cm.
and preferably a pressure of at least 35 kg/sq.cm. It is also preferable that the second elevated pressure be at least 7 kg/sq.cm and that there is a pressure drop between the first and second elevated pressures of at least 20 kg/sq. cm.
With this system the slurry is quickly brought through a gel stage and to liquid form in the tubular heating zone. The purpose of this stage is to bring the slurry into a liquid form of relatively low viscosity but without necessarily any substantial degree of hy-drolyzation. When the hot starch liquid is forced through the restricting zone s~lch that it emerges into the tubular reaction zone in the form of a fine spray or mist with a sudden release of energy, the starch liquid becomes highly activated and the hydrolysis occurs at very high speed in the tubular reaction zone. Not only is the hydrolyzation uniform but can also continue to a high D.~. value while producing a high quality product. Eor instance, D.E. values in the order of 70 can be achieved ~77~7 wit:h c~l~;e while r~ctaitlincJ excellcnt taste, an(3 with Q greater control of the process,D.E. values as hi~h as 95 can be achieved. Moreover, these values are achieved entirely by means of an acid hydrolysis, avoiding the need for the use of enzymes as has normally been re-quired when high D.E. values are desired.
For best results the second elevated pressure is at least 10 kg/sq. cm. and this can be achieved by in-cluding a downstream restricting zone in the tubular 10 reaction zone to control the pressure within that reaction zone. It has also been found that best results are achieved when the slurry is heated to a temperature of at least 125~C. in the tubular heating zone and parti-cularly good results are achieved at temperatures in excess of 135C.
The polysaccharide feed to the process can be selected from a wide variety of materials including processed starches and native starches. Corn starch is particularly desirable because of its ready availability 20 but other starch sources such as potato, wheat, tapioca, rice, etc. are equally satisfactory. Even food processing wastes can be used, such as was~es frDm potato processing plants.
The slurry beiny fed to the system may contain as much as 75% starch solids, although slurries contain-ing more than about 55~ solids produce a very viscous product which becomes difficult to handle in further processing. The slurry can be acidified with an in-organic or organic acid. Typical of the inorganic acids that can be used are sulfuric acid, hydrochloric acid 30 and phosphoric acid, while typical inorganic acids in-clude citric, lactic and acetic acid. ~ydrochloric acid is partiCularly advantageous because of its ready avaiiability.
The product which is obtained is alight amber liquid usually having a solids content in the range of about45-65% by weight. The liquid is easily elari-fied by first neutralizing it to a pH of about 5.5 to 6.5, for example by addition of calcium carbonate. This causes undesirable materials to precipitate and these are readily removed by filtering or centrifuging. The 1~ separated liquid has a clear amber eolor which can be eompletely removed by passing the liquid through aetiva~ed earbon.
Previous acid hydrolysis systems not only lack flexibility for being able to produce a wide range of D.E. values during acid hydrolysis, but also usually produced a product having a solids content no higher than 30-32~. Commercial syrups normally have a solids content of about 55~ and this meant that such products from hydrolysis had to be conoentrated, e.g. by means of a triple-effect evaporator to reach the desired 55%.
Syrups having a solids content of 55~ and a wide variety of D.E. values can be produced directly by the process of this invention.
The temperatures and pressures as well as the acidity can all be used for controlling the D.E. values with the fine control to a particular D.E. value being maintained by means of variations in pressure.
It is believed that the differences in the reaction according to this invention as compared with the prior art has to do with the very high levels of thermal and mechanical energy which are being imparted ~7727 to the s~arcll molecule during its passa~3e through the restricting zone. Starch in its natural state tends to have a highly curled or spiral configuration which interferes with ready access to the reactive points where hydrolysis would normally occur. ~owever, on passing through the elongated confining zone at ele-vated temperatures and high pressures, it is believed that a substantial portion of the curl is removed from the starch molecules and many reactive points are exposed for hydrolysis. With ready access to many more reactive points, it then becomes possible to control the degree of hydrolysis and hence the D.E. value by control of such reaction conditions as the acidity, reaction temperature and reaction pressure.
Certain preferred embodiments of the present invention are illustrated by the attached drawings in which:
Figure 1 is a schematic flow sheet showing ap-paratus for carrying out the invention; and Figure 2 is a partial sectional view of an orifice;
o As will be seen from Figure 1, a holdiny tank 10 is provided for a starch slurry feed. This tank has an outlet 11 which feeds into a continuous flow positive displacement pump 12, such as a Moyno pump manufactured by Robbins & Myers. The slurry is pumped out of pump 12 ~hrough line 13 at high pressure and through a high pressure diverter valve 14.
The valve 1~ is used to regulate the pressure in the inlet 16 to the reactor 17. This is done by bleeding off a portion of the slurry through line 15 and recycling it back into tank 10.
The main reactor 17 is a closed and insulated 7~27 vessel sul)stan~ially filled with a heat exchange fluid such as Therminol 66 ~, av~i1able from the Monsanto Company.
A 12.7 mm I.D. sta~nless steel pipe is used as the reactor tube and this is made up in the form of three coiled portions 18, 20 and 22. Coil 18, w}~ich connects to inlet 16, represents the heating zone and has a length of about 18.3 m. Coil 20 is the tubular reaction zone and has a length of about 12.2 m while coil 22 re-presents a tail zone and has a length of about 6.1 m.
Mounted between coils 18 and 20 is an orifice member 19 while a second orifice member 21 is mounted between coils 20 and 22. It is also possible to use more than two orifices in sequence with an intermediate coil section similar to coil 20 being used between each pair of orifices.
Looking at an orifice member in greater detail, it can be seen that it has a main body portion 29 made from a stainless steel block with cylindrical recesses 33 and 34 for receiving the ends of tubes 20 and 18 respectively. Extending through the length of the body 29 is an orifice hole 30 having a length of about 8.6 cm.
In this particular embodiment, the orifice hole 30 of orifice member 19 has a diameter of 2.5 mm while that of orifice member 21 has a length of 8.5 cm and a diameter of 2.3 mm.
The orifice preferably has a diameter of not more than about 3-6 mm for best results. When a heating coil having a diamRter substantially greater than 12-13l mm ~s used, e.g. 25 mm. or more, the orifice member may include a series or bores therethrough, each having a diameter of ~ 77Z7 prefera~ly not more than about 3-6 mm. The orifice member may also be in the form of a plurality of inlet bores merging into a common single outlet.
The length of each orifice is not critical, and may be no more than a thin plate orifice. However a sub-stantial length of, e.g. 2-10 cm, is generally preferred.
~ o smooth the flow of starch slurry into the orifice hole 30, there is provided an inwardly flared inlet portion 31. There is also provided an inwardl~
flared outlet portion 32 which has been found to also improve the flow. Thus, it has been found that if this flaring on the outlet is not provided, there is a fairly rapid build up of solid material in the vicinity of the outlet. With the flared outlet this does not occur and the slurry emerges in the form of a puff of vapour 35 which then transforms into a homogeneous liquid. A
similar action occurs in orifice 21 with the vapour again forming into a liquid in the coil 22 and a homogeneous liquid product emerging through outlet 23.
The temperature within the reaction zone is con-trolled by means of the heat exchange fluid in the vessel 17. Heat is applied to the heat exchange fluid by re-cycling the fluid via line 24 and pump 25 through an electric heating unit 26 and back into vessel 17 via return line 27. ~ith the heat exchange fluid in vessel 17 being maintained at a predetermined temperature, starch slurry entering through inlet 16 at ambient temperature is heated during its passage through the preheat coil 18 to a temperature which is usually within about 20~C of the bath temperature. A substantial temperature drop of as much as 60~C. can occur across the orifice 19, much of this being recovere<l in th~ reaction tube 20.
I'he following examples are further illustrative embodiments of this invention. All parts and proportions ~re by weiqht unless other wise specified.
Example 1 -- i An acid hydrolysis of starch was carried out using the reactor described in Figure 1 and 2. The coils 18, 20 and 22 were all made from 12.7 mm I.D. stainless steel tubing, with the first coil having a length of 18 m., the second coil having a length of 12.2 m and the third coil having a length of 6.7 m. The first orifice had a diameter of 2.5 mm. and a length of 8.6 cm. and the second orifice had a diameter of 2.3 mm. and a length of 8.6 cm.
A starch slurry was formed from 45 kg pearl corn starch, 47.6 kg water and 240 mls. of hydrochloric acid ( 37~ HCl ). Using a ~loyno pump, this slurry was pumped through the reactor at varying pressures and a bath temp-erature of 190C. This bath temperature of 190C. pro-vided a starch slurry temperature at the inlet of thefirst orifice of approximately 170C. The flow rate through the reactor tube was about 5.6 liters per minute.
The syrups obtained were analysed for D.E. value and the results are shown in Table 1 below.
Bath Temp. Inlet Press. Product C ~q/sa.cm. D .E .
30190 35 53.7 19~ 42 53.2 190 49 43.8 190 56 27.2 11q~t77Z7 ~xample 2 - (a) A starch slurry was formed from 45 kg pearl corn starch, 47.6 kg. water and 220 mls of hydrochloric acid (37% ~ICl). ~sing the same reactor described in Example 1, the above slurry was pumped through the reactor at var~ing pressures, and a bath temperature of 225C., providing a slurry temperature at the inlet to the first orifice of approximately 200C.
Thy hydrolysates obtained were analysed for D.E.
value as well as for composition in terms of contents of dextrose, maltose, tri-saccharides, tetra-saccharides, and higher saccharides. The results are given in Table 2 below:
TA~LE 2 _ _ _ _ Product Anal sis _ Bath Inlet D.E. pH Dext- Mal- Tri- Tetra/Penta Temp. Press. rose tose haCCd~ Saccharide C. kg/sq.cm % % ~ %
. ..._.
225 42 78.5 3.41 67.1 22.4 9.1 0 49 78.1 5.6* 66.5 22.3 9.8 0 56 71.9 3.1 57.8 22.8 18.1 _ * Neutralized (b) Comparative Analysis:
As a comparison, a sample of commercial hydrolysed starch was also analysed. The sample was a syrup available from St. Lawrence Starch, Montreal, under the trademark Hidex Glucose, containing 81% solids and rated at a D.E.
value of 65. The results of the analysis are given in Table 3 below:
1~7727 O ~ D.E. Value 60.8 Dextrose ~ 37.3 Maltose % 22.1 Trisaccharide ~6 12.1 ;
Tetra/Penta 28.3 Saccharide %
_ __ ~
Example 3 A series of trials were run again using the same reactor described in Example 1, to determine the effects of different reaction temperatures on D.E. values at a fixed pressure. The starch slurry feed contained pearl corn starch in an amountof 43~ solids, and was acidified with 136 mls hydrochloric acid per 45 kg. dry starch.
The pressure at the inlet to the first orifice was maintained at about 52 ky/cm and the slurry temp-erature at this point was varied between 140C. and 157C.
20 The product was neutralised to a pH of 4.5 to 5.4 using a 10% sodium carbonate solution. After neutralization, the product was filtered through a cloth filter under 68.6 cm of vacuum, the filter cloth being precoated with diatomatious earth. After filtration, the product was pumped through a series of t~ree (3) carbon columns, given a final pH adjustment and evaporated to approximately 80%. The results obtained are shown in Table 4 below.
. _ ... ._ ._ , . .. ._ Head Press.~kg/sq.cm ) 52.5 52.5 49 52.5 52.5 Liquid Temp (C) 145 157 153 146 140 D.E. after reactox 40.25 62.2 52.7 40.8 27.75 Solids after reactor (~) 56 57 _ 57 Final Product D.E. 38.2 67 56.7 42.4 2 8 1~7727 E~amplc 4 test was conducted to determine the effects of coil lengths and orifices on the hydrolysis of starch slurries.
(a) ~ first series of trials were run utilizing on~y the heating coil 18 and the orifice 19 with the outlet from the orifice 19 being directed to a collection ~ank.
Heating coils 18 of varying lengths were used and the orifice 19 has a diameter of 2.6 mm. and a length of 7.6 cm.
The material fed was a mill stream corn starch slurry at 38.2~ solids with an acid level of 136 mls/45 kg dry starch solids. The flow rate, viscosity and D.E.
of the product were measured and the results were as follows:
. _ ._ _ H~ating Coil Flow Rate Viscosity Bath Temp Liquid Press. D.E.
Length ( m)Q / m i n . C . P . @ 96 C C ~ Temp . C kg/sq . cm _ 12 . 2 nil 3600 175 _ 49 0 24 .4 3.8 1080 185 125 38.5 0 2036.6 3.2 270 175 125 40.2 0 42.7 3.0 ll~ l75 126 43.7 0 It will be seen from the above trials that no hydrolysis of the starch occurred.
(b) Using a heating coil 18 having a lenyth of 42.6 m and a first orificeil9 having a diameter of 2.6 mm. and a length of 7.6 cm, there were added reactor coils 20 of varying lengths and a secondary orifice 21 having a diameter of 2.3 mm.
and a length of 7.6 cm.
The same feed was used as in part (a) above and again the flow rate, viscosity and D.E. of product were measured. The results were as follo~s:
~77Z~
Reactor CoilFlow Rate Viscosity Bath Temp I.iquid Press. D.E.
Length (m)Q/min. C.P.@ 96C C. Temp kg/sq.cm _ _ _ .
0 2.7 37.5 175 150 45.5 8.10 12.2 2.4 _ 175 162 45.5 ~4.1 24.4 2.4 7.5 175 161 45.5 45.7 36.6 2.1 _ 175 156 b5.5 46.3 From the above table it will be seen that as the reaction tube is increased in length up to a length of about 80 feet, there is a very rapid increase in the degree of conversion of starch.
Example 5 Using the same reactor as in Example 4 a further series of tests were carried out with a 42.6 m heating tube and a 36.5 m reaction tube, both having an inside diameter of 12.7 mm. The first orifice had a diameter of
The process adopted in most existing plants for the conversion of starch is a batch process involving hydrolysis with dilute acid. In recent years, various forms of continuous processes have been developed such as that described in Kroyer, U.S. Patent 2,735,792, issued February 21, 1956. A problem with all of these systems has been tha~ of achieving uniform hydrolyzation. Also, whether a batch process or one of the known continuous processes is used, the maximum dextrose e~uivalent (D.E.) which can be reached during acid hydrolysis is about 50.
Attempts to produce D.E. values above 50by acid hydrolysis result in an unsatisfactory product.
Because of this problem, enzymes are now widely used for starch hydrolysis. Thus, it is commonplace to carry out an initial acid hydrolysis to a D.E. value of 50 or less and then continue with one or more enzyme conversions to produce higher ~.E. values. It is also known to use enzymes both for liquification and sacchari-fication.
Enzymes have also not been the full answer to the problems of starch hydrolyzation in that they are unable to act on retrogradation products and many of the enzymes capable of hydrolyzing the glucosidic linkages in the starch molecules are unable to hydrolyze all of the 1,4 and 1,6 bonds. Moxeover, various other enzyme systems may synthesize appreciable amounts of di- or trisaccharides from dextrose or maltose, thereby pre-venting complete hydrolysis to dextrose. It is bel-ieved that these 2roblems are further compounded by the fact that the starch molecules have a curled or spiral configuration which interferes with any access by the enzymes to the reactive points where hydrolysis would ~ormally occur.
It is the object of the present invention to provide an improved process for the hydrolysis of polysaccharides, such as starch.
Thus, the present invention in its broadest aspect relates to a process for the conversion of poly-saccharide materials, such as starch, into dextrose-containing products, which comprises continuously moving an aqueous acidic polysaccharide slurry through a tubular heating zone at a pressure substantially above that of saturated steam to raise the temperature of the slurry to at least 100C., thereby causing the starch slurry to at least partially gelatinize and thereafter form into a hot starch liquid. According to the inventivP feature, the hot starch liquid from the tubular heating zone is at a first elevated pressure of at least 20 ~g/sq. cm. forced throu~h a restricting zone having a cross-sectional area less than 25~ of the cross-sectional area of the tubular heating zone and into a tubular reaction zone having a second elevated pressure substantially below that of the first elevated pressure whereby a highly reactive starch liquid emerges from the restricting zone into the tubular reaction zone in the form of a fine spray or mist with a sudden release of energy. This highly reactive starch liquid is . , ; ~.~r ~' 1~77Z7 continuously moved through the tubular reaction zone to form a homogenous dextrose-containing product.
The restricting zone is preferably in the form of a restricting orifice having a cross-sectional area significantly smal]er than that of the tubular heating, zone, e.g. less than 25% of the cross-sectional area of the tubular heating zone. It has also been found ad-vantageous for the orifice to have substantial length relative to its cross-sectional area, e.g. a length:
diameter ratlo of at least 4:1, although a ratio as small as 1:1 can be used.
The hot starch liquid entering the restricting _ _ _ _ _ . . ... ..
zone will normally have a pressure of at least 20 kg/sq. cm.
and preferably a pressure of at least 35 kg/sq.cm. It is also preferable that the second elevated pressure be at least 7 kg/sq.cm and that there is a pressure drop between the first and second elevated pressures of at least 20 kg/sq. cm.
With this system the slurry is quickly brought through a gel stage and to liquid form in the tubular heating zone. The purpose of this stage is to bring the slurry into a liquid form of relatively low viscosity but without necessarily any substantial degree of hy-drolyzation. When the hot starch liquid is forced through the restricting zone s~lch that it emerges into the tubular reaction zone in the form of a fine spray or mist with a sudden release of energy, the starch liquid becomes highly activated and the hydrolysis occurs at very high speed in the tubular reaction zone. Not only is the hydrolyzation uniform but can also continue to a high D.~. value while producing a high quality product. Eor instance, D.E. values in the order of 70 can be achieved ~77~7 wit:h c~l~;e while r~ctaitlincJ excellcnt taste, an(3 with Q greater control of the process,D.E. values as hi~h as 95 can be achieved. Moreover, these values are achieved entirely by means of an acid hydrolysis, avoiding the need for the use of enzymes as has normally been re-quired when high D.E. values are desired.
For best results the second elevated pressure is at least 10 kg/sq. cm. and this can be achieved by in-cluding a downstream restricting zone in the tubular 10 reaction zone to control the pressure within that reaction zone. It has also been found that best results are achieved when the slurry is heated to a temperature of at least 125~C. in the tubular heating zone and parti-cularly good results are achieved at temperatures in excess of 135C.
The polysaccharide feed to the process can be selected from a wide variety of materials including processed starches and native starches. Corn starch is particularly desirable because of its ready availability 20 but other starch sources such as potato, wheat, tapioca, rice, etc. are equally satisfactory. Even food processing wastes can be used, such as was~es frDm potato processing plants.
The slurry beiny fed to the system may contain as much as 75% starch solids, although slurries contain-ing more than about 55~ solids produce a very viscous product which becomes difficult to handle in further processing. The slurry can be acidified with an in-organic or organic acid. Typical of the inorganic acids that can be used are sulfuric acid, hydrochloric acid 30 and phosphoric acid, while typical inorganic acids in-clude citric, lactic and acetic acid. ~ydrochloric acid is partiCularly advantageous because of its ready avaiiability.
The product which is obtained is alight amber liquid usually having a solids content in the range of about45-65% by weight. The liquid is easily elari-fied by first neutralizing it to a pH of about 5.5 to 6.5, for example by addition of calcium carbonate. This causes undesirable materials to precipitate and these are readily removed by filtering or centrifuging. The 1~ separated liquid has a clear amber eolor which can be eompletely removed by passing the liquid through aetiva~ed earbon.
Previous acid hydrolysis systems not only lack flexibility for being able to produce a wide range of D.E. values during acid hydrolysis, but also usually produced a product having a solids content no higher than 30-32~. Commercial syrups normally have a solids content of about 55~ and this meant that such products from hydrolysis had to be conoentrated, e.g. by means of a triple-effect evaporator to reach the desired 55%.
Syrups having a solids content of 55~ and a wide variety of D.E. values can be produced directly by the process of this invention.
The temperatures and pressures as well as the acidity can all be used for controlling the D.E. values with the fine control to a particular D.E. value being maintained by means of variations in pressure.
It is believed that the differences in the reaction according to this invention as compared with the prior art has to do with the very high levels of thermal and mechanical energy which are being imparted ~7727 to the s~arcll molecule during its passa~3e through the restricting zone. Starch in its natural state tends to have a highly curled or spiral configuration which interferes with ready access to the reactive points where hydrolysis would normally occur. ~owever, on passing through the elongated confining zone at ele-vated temperatures and high pressures, it is believed that a substantial portion of the curl is removed from the starch molecules and many reactive points are exposed for hydrolysis. With ready access to many more reactive points, it then becomes possible to control the degree of hydrolysis and hence the D.E. value by control of such reaction conditions as the acidity, reaction temperature and reaction pressure.
Certain preferred embodiments of the present invention are illustrated by the attached drawings in which:
Figure 1 is a schematic flow sheet showing ap-paratus for carrying out the invention; and Figure 2 is a partial sectional view of an orifice;
o As will be seen from Figure 1, a holdiny tank 10 is provided for a starch slurry feed. This tank has an outlet 11 which feeds into a continuous flow positive displacement pump 12, such as a Moyno pump manufactured by Robbins & Myers. The slurry is pumped out of pump 12 ~hrough line 13 at high pressure and through a high pressure diverter valve 14.
The valve 1~ is used to regulate the pressure in the inlet 16 to the reactor 17. This is done by bleeding off a portion of the slurry through line 15 and recycling it back into tank 10.
The main reactor 17 is a closed and insulated 7~27 vessel sul)stan~ially filled with a heat exchange fluid such as Therminol 66 ~, av~i1able from the Monsanto Company.
A 12.7 mm I.D. sta~nless steel pipe is used as the reactor tube and this is made up in the form of three coiled portions 18, 20 and 22. Coil 18, w}~ich connects to inlet 16, represents the heating zone and has a length of about 18.3 m. Coil 20 is the tubular reaction zone and has a length of about 12.2 m while coil 22 re-presents a tail zone and has a length of about 6.1 m.
Mounted between coils 18 and 20 is an orifice member 19 while a second orifice member 21 is mounted between coils 20 and 22. It is also possible to use more than two orifices in sequence with an intermediate coil section similar to coil 20 being used between each pair of orifices.
Looking at an orifice member in greater detail, it can be seen that it has a main body portion 29 made from a stainless steel block with cylindrical recesses 33 and 34 for receiving the ends of tubes 20 and 18 respectively. Extending through the length of the body 29 is an orifice hole 30 having a length of about 8.6 cm.
In this particular embodiment, the orifice hole 30 of orifice member 19 has a diameter of 2.5 mm while that of orifice member 21 has a length of 8.5 cm and a diameter of 2.3 mm.
The orifice preferably has a diameter of not more than about 3-6 mm for best results. When a heating coil having a diamRter substantially greater than 12-13l mm ~s used, e.g. 25 mm. or more, the orifice member may include a series or bores therethrough, each having a diameter of ~ 77Z7 prefera~ly not more than about 3-6 mm. The orifice member may also be in the form of a plurality of inlet bores merging into a common single outlet.
The length of each orifice is not critical, and may be no more than a thin plate orifice. However a sub-stantial length of, e.g. 2-10 cm, is generally preferred.
~ o smooth the flow of starch slurry into the orifice hole 30, there is provided an inwardly flared inlet portion 31. There is also provided an inwardl~
flared outlet portion 32 which has been found to also improve the flow. Thus, it has been found that if this flaring on the outlet is not provided, there is a fairly rapid build up of solid material in the vicinity of the outlet. With the flared outlet this does not occur and the slurry emerges in the form of a puff of vapour 35 which then transforms into a homogeneous liquid. A
similar action occurs in orifice 21 with the vapour again forming into a liquid in the coil 22 and a homogeneous liquid product emerging through outlet 23.
The temperature within the reaction zone is con-trolled by means of the heat exchange fluid in the vessel 17. Heat is applied to the heat exchange fluid by re-cycling the fluid via line 24 and pump 25 through an electric heating unit 26 and back into vessel 17 via return line 27. ~ith the heat exchange fluid in vessel 17 being maintained at a predetermined temperature, starch slurry entering through inlet 16 at ambient temperature is heated during its passage through the preheat coil 18 to a temperature which is usually within about 20~C of the bath temperature. A substantial temperature drop of as much as 60~C. can occur across the orifice 19, much of this being recovere<l in th~ reaction tube 20.
I'he following examples are further illustrative embodiments of this invention. All parts and proportions ~re by weiqht unless other wise specified.
Example 1 -- i An acid hydrolysis of starch was carried out using the reactor described in Figure 1 and 2. The coils 18, 20 and 22 were all made from 12.7 mm I.D. stainless steel tubing, with the first coil having a length of 18 m., the second coil having a length of 12.2 m and the third coil having a length of 6.7 m. The first orifice had a diameter of 2.5 mm. and a length of 8.6 cm. and the second orifice had a diameter of 2.3 mm. and a length of 8.6 cm.
A starch slurry was formed from 45 kg pearl corn starch, 47.6 kg water and 240 mls. of hydrochloric acid ( 37~ HCl ). Using a ~loyno pump, this slurry was pumped through the reactor at varying pressures and a bath temp-erature of 190C. This bath temperature of 190C. pro-vided a starch slurry temperature at the inlet of thefirst orifice of approximately 170C. The flow rate through the reactor tube was about 5.6 liters per minute.
The syrups obtained were analysed for D.E. value and the results are shown in Table 1 below.
Bath Temp. Inlet Press. Product C ~q/sa.cm. D .E .
30190 35 53.7 19~ 42 53.2 190 49 43.8 190 56 27.2 11q~t77Z7 ~xample 2 - (a) A starch slurry was formed from 45 kg pearl corn starch, 47.6 kg. water and 220 mls of hydrochloric acid (37% ~ICl). ~sing the same reactor described in Example 1, the above slurry was pumped through the reactor at var~ing pressures, and a bath temperature of 225C., providing a slurry temperature at the inlet to the first orifice of approximately 200C.
Thy hydrolysates obtained were analysed for D.E.
value as well as for composition in terms of contents of dextrose, maltose, tri-saccharides, tetra-saccharides, and higher saccharides. The results are given in Table 2 below:
TA~LE 2 _ _ _ _ Product Anal sis _ Bath Inlet D.E. pH Dext- Mal- Tri- Tetra/Penta Temp. Press. rose tose haCCd~ Saccharide C. kg/sq.cm % % ~ %
. ..._.
225 42 78.5 3.41 67.1 22.4 9.1 0 49 78.1 5.6* 66.5 22.3 9.8 0 56 71.9 3.1 57.8 22.8 18.1 _ * Neutralized (b) Comparative Analysis:
As a comparison, a sample of commercial hydrolysed starch was also analysed. The sample was a syrup available from St. Lawrence Starch, Montreal, under the trademark Hidex Glucose, containing 81% solids and rated at a D.E.
value of 65. The results of the analysis are given in Table 3 below:
1~7727 O ~ D.E. Value 60.8 Dextrose ~ 37.3 Maltose % 22.1 Trisaccharide ~6 12.1 ;
Tetra/Penta 28.3 Saccharide %
_ __ ~
Example 3 A series of trials were run again using the same reactor described in Example 1, to determine the effects of different reaction temperatures on D.E. values at a fixed pressure. The starch slurry feed contained pearl corn starch in an amountof 43~ solids, and was acidified with 136 mls hydrochloric acid per 45 kg. dry starch.
The pressure at the inlet to the first orifice was maintained at about 52 ky/cm and the slurry temp-erature at this point was varied between 140C. and 157C.
20 The product was neutralised to a pH of 4.5 to 5.4 using a 10% sodium carbonate solution. After neutralization, the product was filtered through a cloth filter under 68.6 cm of vacuum, the filter cloth being precoated with diatomatious earth. After filtration, the product was pumped through a series of t~ree (3) carbon columns, given a final pH adjustment and evaporated to approximately 80%. The results obtained are shown in Table 4 below.
. _ ... ._ ._ , . .. ._ Head Press.~kg/sq.cm ) 52.5 52.5 49 52.5 52.5 Liquid Temp (C) 145 157 153 146 140 D.E. after reactox 40.25 62.2 52.7 40.8 27.75 Solids after reactor (~) 56 57 _ 57 Final Product D.E. 38.2 67 56.7 42.4 2 8 1~7727 E~amplc 4 test was conducted to determine the effects of coil lengths and orifices on the hydrolysis of starch slurries.
(a) ~ first series of trials were run utilizing on~y the heating coil 18 and the orifice 19 with the outlet from the orifice 19 being directed to a collection ~ank.
Heating coils 18 of varying lengths were used and the orifice 19 has a diameter of 2.6 mm. and a length of 7.6 cm.
The material fed was a mill stream corn starch slurry at 38.2~ solids with an acid level of 136 mls/45 kg dry starch solids. The flow rate, viscosity and D.E.
of the product were measured and the results were as follows:
. _ ._ _ H~ating Coil Flow Rate Viscosity Bath Temp Liquid Press. D.E.
Length ( m)Q / m i n . C . P . @ 96 C C ~ Temp . C kg/sq . cm _ 12 . 2 nil 3600 175 _ 49 0 24 .4 3.8 1080 185 125 38.5 0 2036.6 3.2 270 175 125 40.2 0 42.7 3.0 ll~ l75 126 43.7 0 It will be seen from the above trials that no hydrolysis of the starch occurred.
(b) Using a heating coil 18 having a lenyth of 42.6 m and a first orificeil9 having a diameter of 2.6 mm. and a length of 7.6 cm, there were added reactor coils 20 of varying lengths and a secondary orifice 21 having a diameter of 2.3 mm.
and a length of 7.6 cm.
The same feed was used as in part (a) above and again the flow rate, viscosity and D.E. of product were measured. The results were as follo~s:
~77Z~
Reactor CoilFlow Rate Viscosity Bath Temp I.iquid Press. D.E.
Length (m)Q/min. C.P.@ 96C C. Temp kg/sq.cm _ _ _ .
0 2.7 37.5 175 150 45.5 8.10 12.2 2.4 _ 175 162 45.5 ~4.1 24.4 2.4 7.5 175 161 45.5 45.7 36.6 2.1 _ 175 156 b5.5 46.3 From the above table it will be seen that as the reaction tube is increased in length up to a length of about 80 feet, there is a very rapid increase in the degree of conversion of starch.
Example 5 Using the same reactor as in Example 4 a further series of tests were carried out with a 42.6 m heating tube and a 36.5 m reaction tube, both having an inside diameter of 12.7 mm. The first orifice had a diameter of
2.6 mm. and the secondary orifice had a diameter of 2.3 mm.
A starch slurry containing 38.2% starch solids and 136 mls HC1/45 kg. dry starch solids was fed through the reactor under the following reaction conditions and results:
Flow Rate Bath Temp Liquid Temp Pressure D.E. Solids Taste Q / m i n . C . C .kg/sq . cm %
. __ . . _ 1.8 184169-17042 45 69 .0 47.8 Fair/Good 1.8 180161-16742-45 56 .9 48.5 Good 1.8 175154-15542-45 41.3 46 .5 Good .
Example 6 A further trial was conducted on a comm~rcial scale reactor with the object of producing a commercial grade corn syrup having a D.E. of approximately 43.
~77Z~
, . . .
ln ti~c commercial reactor the heating tube hada length of 85.3 m. and an outside diameter of 38 mm.
The first orifice consisted of seven (7~ individual orifices in parallel through a stainless steel block, each ori~ice having a diameter of 3.2 mm. and a lengthi of 10 cm. The reaction coil had a length of 122 m. and an outside diameter of 2.5 cm. The second orifice again consisted of seven (7) parallel orifices through a block, each having a diameter of 2.3 mm. and a length of 10 cm.
A starch slurry containing 38.7 % starch solids with a normality of 0.0264 and a conductivity of 3540 micromhos was pumped through the system at a pressure of 45.5 kg/sq.cm and a slurry temFerature at the inlet of the first orifice of 154C.
A corn syrup product was obtained having an average D.E. of 43.8 and a dry solids content of 45-47%. The product flowed at a rate of approximately 38 liters per minute.
Example 7 ~ sing a reactor similar to that of Example 4, a test was conducted using potato wastes from a potato chip plant.
The reactor had 12.7 mm. I.D. tubes with a 55 m.
long heating tube and a 18.2 m. long reaction tube. The first orifice had a diameter of 2.6 mm and the secondary orifice had a diameter of 2.3 mm.
The potato waste slurry containing 38.9% solids at a pH of 1.8 was pumped through the system at a pressure of 25 kg/sq.cm and a slurry inlet temperature to the first orifice of 171C.
A starch slurry containing 38.2% starch solids and 136 mls HC1/45 kg. dry starch solids was fed through the reactor under the following reaction conditions and results:
Flow Rate Bath Temp Liquid Temp Pressure D.E. Solids Taste Q / m i n . C . C .kg/sq . cm %
. __ . . _ 1.8 184169-17042 45 69 .0 47.8 Fair/Good 1.8 180161-16742-45 56 .9 48.5 Good 1.8 175154-15542-45 41.3 46 .5 Good .
Example 6 A further trial was conducted on a comm~rcial scale reactor with the object of producing a commercial grade corn syrup having a D.E. of approximately 43.
~77Z~
, . . .
ln ti~c commercial reactor the heating tube hada length of 85.3 m. and an outside diameter of 38 mm.
The first orifice consisted of seven (7~ individual orifices in parallel through a stainless steel block, each ori~ice having a diameter of 3.2 mm. and a lengthi of 10 cm. The reaction coil had a length of 122 m. and an outside diameter of 2.5 cm. The second orifice again consisted of seven (7) parallel orifices through a block, each having a diameter of 2.3 mm. and a length of 10 cm.
A starch slurry containing 38.7 % starch solids with a normality of 0.0264 and a conductivity of 3540 micromhos was pumped through the system at a pressure of 45.5 kg/sq.cm and a slurry temFerature at the inlet of the first orifice of 154C.
A corn syrup product was obtained having an average D.E. of 43.8 and a dry solids content of 45-47%. The product flowed at a rate of approximately 38 liters per minute.
Example 7 ~ sing a reactor similar to that of Example 4, a test was conducted using potato wastes from a potato chip plant.
The reactor had 12.7 mm. I.D. tubes with a 55 m.
long heating tube and a 18.2 m. long reaction tube. The first orifice had a diameter of 2.6 mm and the secondary orifice had a diameter of 2.3 mm.
The potato waste slurry containing 38.9% solids at a pH of 1.8 was pumped through the system at a pressure of 25 kg/sq.cm and a slurry inlet temperature to the first orifice of 171C.
3~ A product was obtained having a D.E. of 79.1.
Claims (13)
1. A process for producing starch hydrolysates which comprises continuously moving an aqueous acidic starch slurry through a tubular heating zone at a pressure sub-stantially above that of saturated steam to raise the temperature of the slurry to at least 100°C., thereby causing the starch slurry to at least partially gelatinize and thereafter form into a hot starch liquid, characterized in that the hot starch liquid from the tubular heating zone at a first elevated pressure of at least 20 kg/sq. cm. is forced through a restricting zone having a cross-sectional area less than 25% of the cross-sectional area of the tubular heating zone and into a tubular reaction zone having a second elevated pressure substantially below said first elevated pressure whereby a highly reactive starch liquid emerges from the restricting zone into the tubular reaction zone in the form of a fine spray or mist with a sudden release of energy and continuously moving the highly reac-tive starch liquid through the tubular reaction zone to form a homogeneous starch hydrolysate, the temperature and pressure of the hot starch liquid being selectively control-led to provide a starch hydrolysate of predetermined DE
value.
value.
2. A process according to claim 1 characterized in that said tubular reaction zone includes a downstream restricting zone to control the pressure within the reaction zone.
3. A process according to claim 1 characterized in that the first elevated pressure is at least 35 kg/sq. cm.
4. A process according to claim 2 characterized in that the second elevated pressure is at least 7 kg/sq.
cm.
cm.
5. A process according to claim 3 characterized in that the second elevated pressure is at least 10 kg/sq. cm.
6. A process according to claim 5 characterized in that the pressure drop between said first and second elevated pressure is at least 20 kg/sq. cm.
7. A process according to claim 1, 2 or 3 characterized in that the temperature of the hot starch liquid is at least 125°C.
8. A process according to claim 1, 2 or 3 characterized in that the temperature of the hot starch liquid is at least 135°C.
9. A process according to claim 1 characterized in that the restricting zone has a length : diameter ratio of at least 4:1.
10. A process according to claim 9 characterized in that the restricting zone comprises at least one orifice, each said orifice having a diameter of not more than 6 mm.
11. A process according to claim 9 characterized in that the restricting zone comprises a plurality of orifices, each said orifice having a diameter of not more than 6 mm.
12. A process according to claim 11 characterized in that each orifice has a diameter of not more than 3 mm.
13. A process according to claim 11 or 12 wherein each orifice has a length of at least 2 cm.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA294,943A CA1107727A (en) | 1978-01-13 | 1978-01-13 | Continuous production of starch hydrolysates |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA294,943A CA1107727A (en) | 1978-01-13 | 1978-01-13 | Continuous production of starch hydrolysates |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1107727A true CA1107727A (en) | 1981-08-25 |
Family
ID=4110539
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA294,943A Expired CA1107727A (en) | 1978-01-13 | 1978-01-13 | Continuous production of starch hydrolysates |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1107727A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114539431A (en) * | 2022-03-21 | 2022-05-27 | 都江堰天旺食品工业有限责任公司 | Device and method for starch gelatinization |
| CN114573719A (en) * | 2022-03-21 | 2022-06-03 | 都江堰天旺食品工业有限责任公司 | Starch pasting process |
-
1978
- 1978-01-13 CA CA294,943A patent/CA1107727A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114539431A (en) * | 2022-03-21 | 2022-05-27 | 都江堰天旺食品工业有限责任公司 | Device and method for starch gelatinization |
| CN114573719A (en) * | 2022-03-21 | 2022-06-03 | 都江堰天旺食品工业有限责任公司 | Starch pasting process |
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