CA1159382A - Continuous process and apparatus for modifying carbohydrate material - Google Patents

Abstract

Abstract:
A process and apparatus are described for producing a modified carbohydrate material, preferably starch, in fluid form. In the process a starch slurry is continuously moved through a confined tubular preheat zone where heat is very rapidly transferred to the slurry, whereby the slurry passes through a gelation stage and forms into a hot free flowing liquid. The heat transfer is from super-atmospheric steam surrounding at least part of the tubular heating zone, the temperature of the steam and the cross-sectional area of each tubular preheat zone being selected to rapidly transfer heat from the steam throughout the slurry and minimize the magnitude of the zone of high viscosity gel formed during the gelation stage. The hot liquid formed is immediately forced through a restrictive opening and into a confined tubular reaction zone accom-panied by a sudden decrease in pressure whereby the starch is made highly reactive. The reactive starch liquid, together with reactive adjunct such as acid, is then continuously moved through a tubular reaction zone to produce a modified starch product in fluid form. A steam heated reactor for the above process is also described.

Description

~ 1~93~2 Continuous process and apparatus for m _ifying carbohydrate material BACKGROUND OF THE_INVENTION
This invention relates to a process for reacting a carbohydrate material with various modi~ying or deriva-tizing agents. More particularly, this invention relates to a process for producing modified starches and deriva-tized starches in a homogeneous fluid form.
A variety of long chain, high molecular weight carbohydrate materials are ~nown, of which starch is typical. When these are treated with a solvent, usually under pressure, they reach a stage allowing the polymer chain to obtain and maintain many conformational states.
Such a stage is normally associated with a viscosity decrease. The solvent used is usually water, although other solvents can also be used. As this relates to starch, raw starches in their usual commercial form are ; insoluble in water but may be formed into a colloidal or semi-colloidal dispersion by forming a slurry with water and heating the starch slurry to ~n elevated temperature at which the starch granules swell or burst and thus become "gelatinized". The particular temperature re~uired ~or gelatinization depends upon the particular sta~ch se}ected and on other condition~s maintained during ~he gelatinization. The properties of such gelatinized ; di~pcrsions depend upon many factors such as temperature , . . . ..
,. ~, . . : , ; . . .

: , ~, , `

l 1593~2

- 2 -and concentration, and also upon t~e starch material itself and the manner in which the dispersion is prepared.
This gel-forming characteristic of starch slurries when heated has always presented dif~iculties in processes for reacting starch with other reagents. Traditionally these starch reactio~s have been carried out in batch vessels over long periods of time.
There has been some degree of success with continuous starch reactiorls and, for instance, there are on the market continuous starch hydrolyzation systems in which the starch slurry is simply pumped through a long heating coil within which the hydrolysis takes place. Such systems are demanding on plant space, as well as energy and also have limitations as to the degree of reaction that can be achieved. Thus, in hydrolyzing starch, the maximum D.E. value that can be satisfactorily achieved in a system of the above type is in the order of about 50.
When high D.E. syrups are required, e~g. at least 70 D.E.
syrups, an enzyme conversion process has been required.
A significant step forward in the field of starch reactions can be found in the process of Hughes, U.S.
Patent 4,137,094, in the Hughes process a starch slurry is pumped through a primary heating coil whereby it passes through the gelation stage and into the form of a hot free-flowing liquid. This liquid is then forced under high pressure through a restrictive opening into a con-fined tubular reaction zone and this has the effect of greatly increasing the reactivity of the starch slurry.
The Hughes apparatus operated with an oil bath and when this was operated at a moderate temperature of about 170C, satisfactory syrups could be produced up to about 70 D.F.~ ~Iowever, for rapid conversion this could be achieved onl~ at e~cessive pressures of usually more than about 1200 psi and no pumps have been found among the most sophisticated industrial pumps available which do not ~uickly break down under the conditions o~ trying to :~ :L593~32 ~eed an acidic starch slurry at such extreme pressures.
It was found that flow rates greatly increased and pressures dropped by increasing the temperature of the oil bath, but this resulted in a decrease in quality of the syrups produced. For instance, at an oil temperature of 190C., syrups of satisfactory quality could not be obtained above about 60 D.E. The usual commercial syrups have D.E. values up to 73 and for a commercial machine to be entirely useful, it must be capable of continuously produeing a high quality syrup in the 73 D.E. range.
It is the object of the present invention to overcome the above difficulties of the Hughes process.
SUMMARY OF_THE INVENTION
The present invention relates to a continuous process for produeing a modified carbohydrate material in homo-geneous fluid form in which a slurry of carbohydrate material is continuously moved through a confined tubular preheat zone comprising a plurality of braneh lines and heat is rapidly transferred to the slurry in the tubuiar zone whereby it passes through a gelation stage and forms into a hot free-flowin~ fluid having a temperature of at least 125C. The heat is supplied from a steam bath containing steam at a pressure of at least 100 psig and the temperature of the steam and the cross-sectional area of eaeh tubular preheat zone are selected to provide a rapid heating of the slurry such as to minimize the mag-nitude of the zone of high viseosity gel during the gel-ation stage. This hot fluid thus formed is then immed-iately ~oreed through a restrietive opening and into a eonfined tubular reaetion zone aeeompanied by a sudden decrease in pressure whereby the carbohyc~rate material is made highly reaetive. This highly material is eontinu-ou~ly moved, together with a reaetive adjunet, through the tuhular reae~ion zone to procluce a modified earbohycdrate material in ~luLd eorrn.
~ES~RIP'rION OF r~lE. PRF,FERRF.D E~MBO~MENTS
~he earbohydrate material may be selec:ted from the group eonsisting of unmodified earbohydrate material, .

~ 1 593~2 chemically modified carbohydrate material, derivatized car-bohydrate material and mixtures thereof. The most common such material is starch, e.g. corn, potato, tapioca, sago, rice, wheat, waxy maize, grain sorghum, and waxy sorghum.
They can be used in refined form or as natural components in cereal grains. It is also possible to use hemicellulose containing materials, for example, the hull fibers isolated in the wet-milling industry.
The adjunct may be selected from acids, alkalis, salts and mixtures thereof as well as enzymes to produce a modified carbohydrate. Alternatively, the adjunct may be a carbohydrate derivatizing agent such as sodium tripoly-phosphate, propylene oxide, 2,3-epoxypropyl- trimethyl-ammonium chloride, sodium chloroacetate~ epoxychloro-hydrin, acetic anhydride, maleic anhydride, 2-chloroethyl diethylamine hydrochloride, 2,3-epoxypropyl sulfonate, triethylamine, sulfur trioxide and urea.
Some of the molecules of native starches are extremely long and it may be necessary to break these down to a manageable point in the preheat zone. This can be done by means of a cleaving agent, such as an acid, in the carbohydrate slurry.
In a process of the present type, the carbohydrate slurry must pass through a gel stage and thereafter achieve a state of equilibrium. At equilibrium, the slurry has passed through a viscosity peak and has returned to a relatively low viscosity, e.g. less than 500 cps at 90C
immediately after discharge without any substantial reac-tion of the carbohydrate material having taken place.
It is an important feature of this invention that the magnitude of th~ zone of high viscosit~ gel during the gelation stage is kept to a minimum, sirlce this makes it posqible to quickly achieve the state of e~uilibrium without the necessity of using extreme condit:ions of temperature and/or pressure in the preheat zone. ~his requires an extremely rapid heat input into the slurry in the preheat zone without substantial burning of the ,' .

~ , , '

3 ~ 2 carbohydrate and this has been achieved according to this invention by means of individual tubular preheat zones of limited cross-sectional area which pass through a heating bath containing superatmospheric stearn. The steam is gen-erally at a pressure in the range of 100-250 psig, with a pressure in the range of about 100-125 psig being particu-larly preferred. The 100 psig steam provides a bath temperature of 166C, while the 125 psig steam provides a bath temperature of 135C. It is also particularly desir able to use saturated steam, since it provides a greater uni~ormity o~ heatin~
It i5 also important to have the material pass through the preheat zone as quickly as possible since it has been found that long exposures to heating tends to encourage undesirable side reactions. This is particularly important in the hydrolysis of starch, since slow reactions tend to increase the production of materials such as gentiobiose, which gives a bitter taste in the product. With the pro-cess of this invention the carbohydrate slurry is normally ~0 passed through the gel stage and brought to equilibrium conditions at reaction temperature within about 100 seconds, preferably within about 25 to 45 seconds using a 1/~" I.D. preheat tube and within about 50-100 seconds using a 1" I.D. preheat tube. The actual slurry velocity is usually about 0.5 to ~ Et/sec, preferably 1 to 3 ft/sec.
At these equilibrium conditions and desired reaction temperatures, the hot carbohydrate liquid is forced through a restrictive opening and into a confined tubular reaction ~one accompanied by a sudden decrease in pressure. ~his has the effect of greatly increasing the reactivity o~ the carbohyclrate so that it will very quickly react with reactlve adjuncts within the tubular reaction zone. Such adjunct.s may be mixed with the carbohydrate slurry beEore passing through the preheat zone or it may be injected 3S directly into the highly reactive material immediately ~ollowing the restrictive opening.

~ 1~9382 \

The tubular preheat zone can be of any desired con-figuration, provided it is capable of maintaining a continuous flow of material. For instance, it may be a heat exchange tube through which the material is driven by means of a continuous displacement pump. In order to achieve the desired high rate of heat exchange throughout the slurry, the individual heat exchange tubes are prefer-ably of relatively small diameter, e.g. less than 2 inches.
It has been found to be particularly advantageous to use quite small diameter tubes in the range of about 1/2 inch to 1 1/2 inches. With diameters of one inch or more~ it may be advantageous to use static mixers to provide adequate mixing within the tubes.
Moreover, additional heating and mixing of the starch slurry can be achieved by direct injection of steam into the slurry within the tube, e.g. by injecting steam in the region of the preheat zone inlet. This can serve to very quickly raise the tempera~ure of the slurry and will, of course, have some dilution ef~ect on the slurry. The balance of the heating to equilibrium conditions is achieved by indirect heating in a steam bath.
The restrictive opening must have a cross-sectional area significantly smaller than the cross-sectional area oE the individual preheat tubes and each opening prefer-ably has a diameter of less than about 0.25 inch. The restrictive opening between the preheat zone and the reaction zone can be in the form of single opening, or a plurality of adjacent openings may be used.
The temperature oE the material passing through the restrictive opening is at least 125C. and is preferably in the range oE 130 to 170C. for acid hydrolysis of starch. Of course, Eor other reactions the temperatures may vary slgrliEicantly from ~his.
The pressure on thq inlet side to the restrictive opening ls usually at least 300 psi 7 and preEerably at least 500 to 1000 p5i. ~he upper limit is largely `

determined by the capability oE the pump being used to pump the slurry through the system. There is a very marked pressure drop across the restrictive opening and this is preferably in the order of 300-600 psi.
The confined tubular reaction zone can also be of any desired configuration, provided it is capable of maintain-ing a continuous flow of material. It is preferably a heat exchange tube which may pass through either the preheat steam bath or a separate heat exchange bath at the same or different temperature from the preheat steam bath. The reaction tube can be the same size as the preheat tubes or larger or smaller diameter than the preheat tubes, depend-ing on the materials being processed. Generally, the size oE the reaction tube is less critical than i5 the size of the preheat tube since the material entering the reaction tube is already a freely flowing liquid at reaction temperature.
The residence time in the tubular reaction zone of 1/2" diameter is usually less than two minutes to produce - 20 a starch syrup having a D.E. of up to 73 and a high quality syrup of 73 D.E. has been produced according to this invention with-a total residence time in a 1/2" diameter the preheat and reaction zone of less than 2 1/2 minutes.
- It is desirable that the pressure within the reactor be controlled entirely by the feed pump, rather than by any ~orm of pressure responsive recycle loop. I`his can be achieved by means of a variable speed positive displace-ment pump, such as a Moyno pump, with the pressure in the reactor being controlled by the pump speed. In this manner/ the material being processed travels through the reactor as a continuous Eorwardly moving mass.
A better contro:l of this system is achieved if a control is maintained over ~he pressure within the tub~llar reaction zone and this can conveniently be achieved by provlding a further restrictive opening at the outlet end of the reaction zone. The pressure within the reaction zone is preferably maintained at a level sufficient to keep the material in the reaction zone in tlle liquid stage, e.g.
about 200 psi.
Certain preferred embodiments of the present invention are illustrated in the attached drawlngs in which:
Fig. 1 is a schematic flow sheet showing apparatus for carrying out the invention;
Fig. 2 is a schematic representation of one preferred embodiment of the apparatus;
Fig. 3 is a detailed view of a tubular collector arrangement;
Fig. 3a is a sectional view of a preferred collector arrangement.
Fig. 4 is a plot of D~Eo values against residence time in the reactor;
Fig. 5 is a plot of glucose values against residence time in the reactor;
Fig. 6 is a plot of temperature progressions for steam and oil heated reactors;
Fig. 7 is a plot of pressure drops against flow velocities for a steam reactor;
Fig. 8 is a plot of ternperature rise, D.3. values and ~entiobrose amounts for an oil bath heater reactor;
Fig. 9 is a plot similar to Fig. 8 using an oil bath at a higher temperature; and Fig. 10 is a plot similar to Fig. 8 using a steam heating bath.
As will be seen from Fig. 1, a holding tank 10 is provided 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 1~ is control:led by varying the speed of pump 12.
The main reactor oE this apparatus is a closed and insulat~d vessel lS which is essentially a stearn vesse~l heing supplied by a stearn inlet line 16 and a steam oLItlet 93~2 g line 17. A steam control valve 30 is provided in the steam inlet line.
The tube 14 is made of stainless steel and is preferably 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 orifice 18 having a much smaller diameter then the diameter of tube 14. The outlet of the orifice 18 connects to a further stainless steel tube 19 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.
Fig. 2 shows schematically an arrangement for a high capacity apparatus. Since one of the important features of this invention is the very short heating time of the reaction materials, it is most .important to bring the starch slurry through the gel stage and up to reaction temperature as quickly as possibleO This is achieved in ; 25 Fig. 2 by connecting the slurry feed inlet 13 to a manifold consisting of two branch lines 22 and 23. Each of these branch lines is further divided into three additional branch lines 24, 25 and 26 within the heat exchange vessel. Thus, there are six preheat coils passing through vessel 15. This provides very quick heat transfer between the steam and the slurry passing through the coils.
Eactl group of three coils discharges i.nto a single outlet tube 27 and 23 and these in turn feed into a sincJle outlet line 2~ which feeds into the first ori.~ice 13. I.rhe remainder of the reaction then continues in the same ~ ~93~2 manner as described above in Fig. 1.
Since the viscosity of the material being processed varies widely as it passes through the preheat zone, it is most important that the sizes of the tubes be such that at any point in the process there will be a constant velocity across all of the tubes. Thus, at the outlet of tubes 24, 25 and 26, it will be seen from Fig. 3 that the sizes of tubes 24, 25 and 26 on the one hand and tube 27 on the other hand must be such that the velocities in all four tubes will be constant. The same must be true for the three preheat tubes feeding into line 28 and the flow in lines 27 and 28 must also be at the same velocity so that the materials emerging from the various tubes will all be at the same stage of processing when they enter into line 29 and the first orifice 18.
The main branch lines 22 and 23 may include valves so that either one or both lines may be used~ Moreover, these lines 22 and 23, along with lines 27 and 2B, may include couplings so that individual bundles of tubes 24, 25, 26 may be removed for maintenance. With a bundle removed, the remainder of the reactor can continue operating.
A preferred form of collector from the multiple preheater reaction tubes is shown in Figure 3a. A problem that can be encountered when a series o~ tubes discharge into a single outlet tube is that if conditions within the multiple tubes are not absolutely identical, there may be a tendency for more rapid flow through one of the tubes than the others and this will then tend to channel into the outlet tube in preference to the slower tubes, resulting in a product which lacks homogeneity.
The co~lector in Figure 3a is in the ~orm o~ a trun-cated ccnical vessel 31 with the outlets of tubes 2~, 2S
and 26 connecting to the large encl o~ vessel 31 at an angle to the axis of the vessel. In this manner the streams from tubes 2~ r 25 ancl 2~ impinge upon each other 3 ~ 2 within vessel 31 thereby causing a uniform mixing at this point and discouraging any tendency of any single stream from one o~ tubes 24, 25 and 26 to channel directly into outlet tube 27. This collector vessel can be used at any point in the system where discharges from two or more tubes are being directed into a single tube.
The above systems show the reaction tube passing through the same heat exchange bath as the preheat tubes.
It is, however, to be understood that depending on the reaction being carried out, the reaction tube may be par-tially or totally outside the heat exchange bath or may pass through a separate bath maintained at a temperature different from the preheat bath.
The following examples are further illustrative embodiments of this invention. All parts and proportions are by weight unless otherwise specified and all pressures are gauge pressures 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 1/2" I.D. stainless steel tubing with coil 14 having a length of 120 feet and coil l9 having a length 40 feet.
The first orifice had a diameter of 0.062 inch and the second orifice was in the form of a pair of adjacent open-ings, each having a diameter of 0.062 inch.
A starch slurry was formed from starch and water, this slurry containing 36.1~ starch solids. 200 mls oE hydro-chloric acid were added to the slurry per lO0 pounds of starch solids and this gave a slurry conductivity oE 4100 micromhos at 30C. This slurry passed through the reactor a~ a rate of 1.6S gallons per minute under the following reaction condi~ions:

~ 1~93~2 TABI,E 1 REACTOR CONDITIONS:
Temperatures:
Steam supply 167C
Steam after control valve 163C
Steam bath (bottom)160C
Steam bath (top) 160C
1st orifice inlet 148C
' 1st orifice outlet148C
2nd orifice inlet lS9C

Pressures:
Steam supply 100 psig Steam after control valve 82 psig Feed pump outlet1000 psig lS 1st orifice inlet750 psig , 1st orifice outlet470 psig The hot starch liquid immediately before the first orifice 18 had a viscosity of approximately 25 cps at , 80C. The product obtained had a D.E. of approximately 14.
(b) The above apparatus was modified to provide a preheat coil 80 feet long and reaction coils of varying lengths. With this arrangement, the residence time in the preheat zone was about 33 seconds and the total residence times in the reactor varied between 50 and 140 seconds.
The starch slurry feed contained 36.4% starch solids and runs were made with 140 and 200 mls of hydrochloric acid per 100 pounds of starch solids in the slurry. The steam bath temperature was 166C., and the feed pump ; outlet pressure was 900 psi. This produced D.E. values ranging from about 15 to about 73, with the product being of excellent quality. The D.E. results are plotted on Fig. 4 and these s.how the very rapid generatian of D.E.
values wi~hin the reaction tube. Flg. 5 shows a separate plot o~ gluco~e fractions in the products from the above production runs.

9 3 ~ ~

F,xample 2:
(a) A series of additional test were carried out on the same apparatus as described above to produce corn syrups having D.E. values in excess of 70.
Again using half inch tubes, a test was carried out using a preheat coil having a length of 80 feet and a reactor coil having a length of 280 feet. The first orifice had a diameter of 0.062 inch and the second orifice consisted of two adjacent holes each having a diameter of 0.062 inch.
An aqueous starch slurry feed was prepared containing 34.8~ starch solids and 190 mls of hydrochloric acid were added per 100 pounds of dry starch sollds. This gave a conductivity of 3450 micromhos.
This slurry was pumped through the reactor at a flow rate of 1.5 gallons per minute under the following reaction conditions:

Reactor Conditions:
Tem~erature-Steam supply 330F
Steam after control valve 330F
Steam bath (bottom) 167C
Steam bath (top) 165C
1st orifice inlet 145.6C
1st orifice outlet 145.9C
2nd orifice inlet 162C

Pressures:
Steam supply 99 psi Steam after control valve g7 psi Feed p~mp outlet 900 psi 2nd orifice inlet 200 psi ~ 'he prod-lct obtained was a corn syrup having excellent taste with a D~E.of approximateLy 74. The product had a solids content of 44 to 45~.

- ~ ~5~3~2 (b) The above test was repeated using a preheat coil having a length of 80 feet and a reaction coil having a length of 240 feet. Otherwise the apparatus was unchanged.
The feed slurry was a pearl corn starch slurry containing 35.9% dry solids and 200 mls of hydrochloric acid per 100 pounds dry starch solids. This was pumped through the reactor at 1.45 gallons per minute with a first orifice inlet temperature of 146C.
The product obtained had a D.E. of about 73, containing 48.4% glucose.
(c) The process was repeated using a preheat coil having a lenqth of 120 feet and a reaction coil having a length of 240 feet. Again the remainder of the apparatus was unchanged. The feed slurry contain 35.5~ dry solids ; 15 of pearl corn starch and had added thereto 190 mls of hydrochloric acid per 100 pounds dry starch solids. This was fed through the reactor at a rate of 1.57 gallons per minute and a first orifice inlet temperature of 161C.
The product obtained had a D.E. of about 72 and contained 49.88% glucose and 19.37% dimers.
Exam~le 3:
.~
A series of studies were conducted using the same apparatus as described in Example 1 above to determinerate of temperature rise of the starch slurry within the preheat coil and reaction coil. The slurry contained about 37% dry starch solids and runs were made with slurries containing 140 and 200 mls HCl. The flow velocity was about 2.6 ft/sec.
These tests were conducted using a steam bath and an oil bath for heat exchange at bath temperatures of 160C.
and 167C. The results obtained are sho~n in Fig. 6.

A test was carrie~ out to illustrate the importance Oe rapid heat input in the preheat æone. The reactor o~
Examplq 1 was used with a preheat coil having a length of 80 feet.

3 ~3 ~

The feed slurry contained 37~ dry starch solids and 200 mls of HCl per 100 pounds starch. The steam bath had a temperature of 165C. The sl~rry was pumped through the reactor at different velocities and the pressure drops across the system were recorded, the results being shown in Fig. 7.
These show that with increasing velocities, there are very large increases in pressure drop. The very large pressure drops require very high inlet pressures with resulting heavy loads on the pump and other equipment.
Thus, the faster is the heat transfer in the preheat zone, the faster the slurry passes through the gel stage and the less is the total energy required to drive the rnaterial through the tube.
EXAMPLE 5:
A series of tests were carried out to directly compare the use of oil and steam baths in the production of starch syrups. The aim of these tests was to produce high quality syrups up to 73 D.E.
The equipment used was generally the same as that described in Example 1, using 1/2" I.D. stainless steel tubing for both the preheat zone and the reaction zone.
The first orifice at the start of reaction zone had a diameter of n. 062 inch and the second orifice at the end of the reaction zone was in the form of a pair of adjacent openings, each having a diameter of 0.062 inch. The pre-heat zone in each test was heated either by recirculating oil or 100 psi saturated steam.
The steam heated reactor and one of the oil heated reactors used a preheater coil length of 80 feet while the second oil bath reactor used a preheater coil length of 120 Eeet ~arying reaction zone lengths were used from ~0 to ~80 Eeet with static mixers located at the ~0 footl 80 foot and 120 foot point oE the reaction zone.
A starch slurry was Eormed from starch and water, this slurry containing 3~% starch solids. ~00 mls o~ 36~

~g3~2 \
~1 E~ ~ *
U) ~ ~ U) U~ ,q U

~ E~ ~ IJ~ rc~
~ ~ 1-- 1` ~0 1-- CO ~
O P~; ~ ~ ~ ~ ~ O O
~-:1 ~ t~ u~ 1~1 o ~I 0 ~1 O ~ .
C,) t,) ::~ o t~
. H
X ~ U~
a a ZU~ ~ a~
o C~
o r~
U~ ~ ~ ~ O l_ ~ m Z E~
o ~ ~
c,) H Z O O O O O O
;'l O ~Ll ~:) o ~D ~`I O'~
U~ ~) U~ W ~D O ~D
r~ ~ o ~ 1-- ~
~ u~ a~ o o o o o H ~ ~ ~ ,_1 ~i ~J

E~
.
E~ o E~ ~r o ~ o 1-- o m ~ ~ ~
~c ~ ~ O O O O O O
E~ O

U~ ~ P~ ~ P~
U~ O O O O O ~

J-a H ~l H H H H
O U~ P~ ~ PJ
~1 H ~ O O O O O O Ll t~ ~ r~ ~
--1 ~ ~1 ~ ~Ir~l 1: 0 r ) C) L~ ~1 E~ o o U ~ O
D P~ o o o o :~ ro u~
a :~
O 1 ~1 ~ D ~ ~I N .~J
P; ~ ~-1 r~ L~
P~ ~1 aJ
ra O O 1:~ Ll 111 n InL~ (~
o o o o rt~ lJ
In r-l ~-1 t.'~ St ra tU
p:~ ~ ~ ~ tl) t~ ~ r ~ N
c~l ~ 3 r-1 r~l r-l R O
tl\ 1 t~ U C~ U t, ) ~; t,U
O O O O O O Ll 1 t~ )t~ t) cr~ ~ ~ ~ tJ~
r-l ~l ~1 ~ ~ ~ )c - 17 ~ 9 3 ~3 2 E~ ~ ~e *
U~ ,, ~ ~ ~ U~ U~

~ r~ ~
:~ H r` O ~ 0!) :5 O P:; ~ ~ ~ O O
O ~ O~ ~ ~ ~ I ~ .
~ CO ~ ~ ~ ~ 0:) . H
O C~
~:1 01 co o~
~1 æ c o ~
C~ ~ o o ~ ~ ~ cn ~ o ~ ~ a~
U~
Z E~ ~ ~ ~4 o ~ C~
~_) H Z
o ~q ~r o f`~
U~
~; o r ~ o u~
~ u~ ~ ~r ~ ~ ~ o~
H `-- ~D ~ 9 ~ ~ Ll~

~r E~ V V V
~: O E~ ~ In 1- c~ oo ~
~ ~ O O O O O O
E~ O
H H H H H H
a u~
E~ oooooo In o o u~

~ H H H 1--1 H H
O u~ u~
~ cn ~ ~ ~ P~
Z ~ O O O O O O ~
OOOOOO

E-- O O
U C~ ~ O U U U
~ Pl o o o o O O 1 O ~ CO 0~ CO r-- I`
~:; E-( ,-1 r-l ,-~ r-l ~Ir~
~1 O ~
U N
o ~) .q P~ V U U U N C~ 1 o o ~ o O ~l ~, ,., ~ ~ Ln r~ a~
~1 ~ t,) N
~-~ r-l o r-l r-~
~-~ ~1 ~I rl r~
U U U U U C~
O O O o O O ~ ~
:q ~ o o~ ~ o ~r n ~ U
O O O O c~
m E~ c~
~1 ~ r~ ~1 ~I r~

.

- 18 - ~ ~593~2 E~
E~
:~
~ H O ~) ~1 O tr; a~
~ ~ ~ ~ ~ ~.~ O O O O
O 1. l ~_ oIrl ~ ) 0 ~1 0 ~1 .
U C) H I

X ~ ~ o ~g ~ ~r ~ C
a ~
a _ Z U~ 1 o c~ ~ ~n co ~ ~ O

Z E~
O ~ ~ O O O O O O O
~ o r~ cO ~ O
-~ U~
H -- I ') ~ ~ (~ ~ ~') lY; P:;

u~~ ~ ~ ~ ~ ~ ~ v ~ m o E~

~ . ~ ~ ~ ~i U~ H H H H H H 1--I
P~ ~ P~
~: ~
~; O - O O O O O O

a 1~1 t-l H H 1-1 H H H ~
O U~ U~ O U) H ~1 J~
O O O C:~ O O O .5 3 w U C~
E-l o o o o o O~I h V C) t~ ~n d' c~ ~1 Ir~
~ o O r~

o aJ
OU O O O O ~
Q ~ Ln L~) U ~_)Irl ~ Ln .I J O
O O . .,L~
P;l r~l ~l r~ r-l t~
t' ~'";t~ ~rl ~1 r-l r-l r-l r-lr-J r-l r-/ r~
U~

O 1~ 0 0 0 0 0 a.~ 1~
5~ p~ r~ a~ a~ r~ Ln ~ ~ ~ rl r~ r l r~ ~I r~ r~

3 ~ ~

hydrochloric acid were added to the slurry per 100 pounds of starch solids and this slurry was passed through the reactor.
The details of the reaction conditions and the results obtained are set out in Tables 3, 4 and 5 below.
Table 3 represents a test procedure showing the production of a marginally acceptable syrup of 73 D.E.
using an oil bath. In this testl the oil bath was maintained at about 169C and a manifold pressure of 1200 psi was required to maintain a flow rate of about 0.7 gpm~
This high pressure caused frequent pump failures using a Monyo positive displacement pump.
In Table 4 is shown the conditions and results from raising the oil temperature in the bath to approximately 190C. Here a flow rate of 0.7 to 0.8 gpm was maintained with a manifold pressure of only 900 psi, but all of the high D.E. syrups exhibited a burned carmelized flavor and aftertaste.
In Table 5 is shown the results from a test carried out using a steam bath containing 100 psi saturated steam at a bath temperature of 166-167C. This provided a much higher ~low ra~e of about 1.45 gpm at a manifold pressure of only 810 psi and quality products were produced up to 73 D.E. In fact, the oil bath required about 273 seconds to produce a 73 D.E. syrup, while the steam reactor produced a 73 D.E. syrup oE equal or better quality in only 148 seconds.
Attached Figures 8, 9 and lU rapidly illustrate the above points. These charts show temperature rise vs.
time, D.E. rise vs. time and percentage gentiobiose in the product. The amount of gentiobiose is an excellent indicator oE the degree oE bitter taste in the product~
Zero time in the time scale repre~ents the e~uilibrium state and is the loca~ion n~ the restriction zone and entry to the reaction zone. Thus, the region to the le~t oE zero time represents the ~reheat zone and the region 93~2 to the right of zero time represents the reaction zone.
Figure 8 shows the results using an oil bath at 169C, Figure 9 shows the results using an oil bath at 190C and Figure 10 shows the results using a steam bath at 167C.
From Figure 8 there will be noted a very large area under the temperature curved to the leEt of zero time. This indicates a very large zone of high viscosity gel which, of course, causes a very high viscous drag resulting in the very high pressure requirements to drive the material through the tube. It will also be noted from Figure 8 that the D.E. rises relatively slowly with time in the reaction zone.
Figure 9 shows the oil bath at 190C and this higher bath temperature has been quite successful in decreasing the zone of high viscosity gel as illustrated by the greatly decreased area under the temperature curve to the left of zero time. A quite rapid increase in D.E.
with time in the reaction zone is also noted. However r one of the most noteworthy features of Figure 9 is the greatly increased production of gentiobiose as compared with Figure 8 and this graphically illustrates one of the reasons why increasing oil bath temperature was not a solution to the problems encountered.
Figure 10 illustrates the steam bath of this invention and compared with Figures 8 and 9 it will be seen that the area to the left of zero time under the temperature curve is even smaller. This indicates a further reduction in the zone o~ high viscosity gel and provides the reason for the rapid flow through the steam system at relatively moderate bath temperatures. Again, a very rapid increase in ~.E~ is noted with time and a relatively small amount ;~ of ~en~iobiose is produced, E~__6:
To shc)w the effects oE increased tube diametcrs in the preheat zone, a series of tests were conclucted on a commercial unit of ~he type shown in Figure ~ containing ~ 1 ~93~2 nine parallel 1" I.D. preheat tubes having a length oE 160 feet. The steam bath was operated at pressures between 100 and 125 psig.
A starch slurry was formed from starch and water, the slurry containing 37% starch solids and 210 mls hydro-chloric acid per 100 pounds of starch solids. The slurry was fed through the system of preheat tubes at different flow rates of 20, 23 and 25 G.P.M. and the steam bath temperature (TBj and the temperature within the preheat tubes immediately before the orifice (TH) were measured.
The results obtained are given in the table below:
PREHEAT
FLOW RATE RESIDENCE TB TH
(G.P.M.) (Sec) (C) (C) -

Claims (24)

We claim as our invention:

1. In a continuous process for producing a modified carbohydrate material in fluid form, which comprises continuously moving a slurry of carbohydrate material through a confined tubular preheat zone comprising a plurality of branch lines and transferring heat to the slurry whereby it passes through a gelation stage and forms into a hot free flowing liquid having a temperature of at least 125°C., immediately forcing said hot liquid through a restrictive opening and into a confined tubular reaction zone accompanied by a sudden decrease in pressure whereby the carbohydrate material is made highly reactive and continuously moving the highly reactive carbohydrate material, together with a reactive adjunct selected from acids, alkalis, salts and enzymes, through the tubular reaction zone to produce a modified carbohydrate material in fluid form, the improvement which comprises transfer-ring the heat to the slurry from steam at a pressure of at least 100 psig, surrounding at least part of said tubular preheat zone, the temperature of the steam and the cross-sectional area of each tubular preheat zone being selected to rapidly transfer heat from the steam throughout the slurry and minimize the magnitude of the zone of high vis-cosity gel formed during the gelation stage.

2. A process according to claim 1 wherein the carbo-hydrate material is a starch.

3. A process according to claim 2 wherein the starch material is raised to a temperature of 130 to 170°C in the preheat zone.

4. A process according to claim 2 wherein the steam is at a pressure of about 100 to 125 psig.

5. A process according to claim 2 wherein the steam is saturated steam.

6. A process according to claim 2 wherein each tubular preheat zone has a diameter of not more than 1 1/2 inches.

7. A process according to claim 6 wherein the starch material is moved through the preheater at a speed of 0.5 to 4 ft/sec.

8. A process according to claim 7 wherein the starch slurry in the preheat contains 10 to 50% dry solids.

9. A process according to claim B wherein the hot free-flowing liquid from the preheat zone has a viscosity below 500 cps at 90°C. immediately after discharge.

10. A process according to claim 9 wherein the pressure at the inlet to the preheating zone is at least 300 psi.

11. A process according to claim 10 wherein the restric-tive opening comprises at least one opening, each said opening having a diameter of no more than 0.25 inch.

12. A process according to claim 7 wherein the starch slurry is raised to a temperature of at least 130°C.
within about 100 seconds in the preheat zone.

13. A process according to claim 7 wherein the starch slurry is raised to a temperature of at least 130°C.
within about 45 seconds in the preheat zone.

14. A continuous process for producing a modified starch material in fluid form, which comprises continuously mov-ing a starch slurry through a confined tubular preheat zone having a diameter of no more than about 1 1/2 inches at a speed of 0.5 to 4 ft/sec, transferring heat to the slurry in the preheat zone from a steam bath containing saturated steam at a pressure of least 100 psig whereby the slurry passes through a gelation stage and reaches an equilibrium stage in the form of a hot free flowing liquid having a temperature of at least 125°C, immediately forcing said hot liquid through a restrictive opening and into a confined tubular reaction zone accompanied by a sudden decrease in pressure whereby the starch liquid is made highly reactive and continuously moving the highly reactive starch liquid, together with an acid through the tubular reaction zone to produce a modified starch product in fluid form.

15. A continuous process for producing starch syrups of D.E. values up to at least 73, which comprises continuously moving an acidified starch slurry through a confined tubu-lar preheat zone having a diameter of no more than about 1 1/2 inches at a speed of 0.5 to 4 ft/sec and transferring heat to the starch slurry from a steam bath containing saturated steam at a pressure of at least 100 psi whereby the starch slurry passes through a gel stage and reaches an equilibrium stage in the form of a hot free flowing liquid having a temperature of at least 125°C, immediately forcing the hot acidifed starch liquid through a restric-tive opening and into a confined tubular reaction zone accompanied by a sudden decrease in pressure whereby the starch is made highly reactive and continuously moving the highly reactive material through the tubular reaction zone to hydrolyze the starch into a starch syrup.

16. A reactor adapted for use in a continuous process for producing a modified carbohydrate material in fluid form comprising an elongated tubular preheater having a plur-ality of heat exchange flow tubes passing through a heat exchange vessel, said heat exchange vessel being adapted to receive super atmospheric steam, a feed inlet to said preheater comprising a tube member connected by way of a manifold to inlets of said plurality of heat exchanger flow tubes, an outlet from said preheater comprising a outlet tube member connected by way of a manifold to outlets of said plurality of heat exchanger flow tubes, the sizes of the feed inlet tube, the outlet tube and the flow tubes being arranged such that the velocities through the heat exchanger flow tubes are substantially equal, a first flow restricting orifice connected to said single outlet tube, an elongated reaction tube having the inlet thereof flow connected to said first orifice outlet and positive displacement pump means connected to said feed inlet tube.

17. A reactor according to claim 16 wherein said heat exchange vessel includes a plurality of said inlet tube members and a plurality of said outlet tube members, each pair of inlet and outlet tube members having a plurality of said heat exchanger flow tubes connected therebetween.

18. A reactor according to claim 16 wherein said plurality of inlet tube members are flow connected to a single feed pump.

19. A reactor according to claim 18 wherein said pump is a variable speed pump, the speed of the pump being used as a pressure control means for the reactor.

20. A reactor according to claim 19 wherein each of said preheater flow tubes has an inside diameter of no more than about 1 1/2 inches.

21. A reactor according to claim 17 including valve means for individually closing said plurality of inlet tube members.

22. A reactor according to claim 16 wherein said elongated reaction tube passes through the heat exchange vessel containing the preheater.

23. A reactor according to claim 16 wherein said elongated reaction tube passes through a separate heat exchange vessel.

24. A reactor according to claim 16 including a continuous flow collector connected to said flow tube outlets, said collector having a truncated conical shape with a closed large end and an open small end, the open small end con-necting to said outlet tube member, and said flow tubes connecting through openings in said large end, said flow tubes adjacent said openings being inclined toward the axis of the collector such that the flows from the flow tubes intersect within the collector.