IMPROVED ENZYME THINNED STARCHES

WIPO Patent Application WO/2000/012746

Abstract

The invention provides a method of preparing a stable enzyme-thinned starch dispersion characterized by a selected degree of thinning including the steps of: (a) combining a derivatized granular starch with an alpha-amylase enzyme to form a starch/enzyme slurry; (b) passing said starch/enzyme slurry through a jet cooker under conditions selected to gelatinize the starch; (c) treating the starch/enzyme slurry to complete gelatinization and achieve the selected degree of thinning such that the concentration of starch hydrolyzate product having a molecular weight greater than 1,000,000 daltons is 5 % or greater; and (d) deactivating the enzyme.

Claims

WHAT IS CLAIMED IS:

1. A method of preparing a stable enzymethinned derivatized starch dispersion characterized by a selected degree of thinning comprising the steps of : (a) combining a derivatized granular starch with an alphaamylase enzyme to form a starch/enzyme slurry ; (b) passing said starch/enzyme slurry through a jet cooker under conditions selected to gelatinize the starch; (c) treating the starch/enzyme slurry to complete gelatinization and achieve the selected degree of thinning such that the concentration of starch hydrolyzate product having a molecular weight greater than 1,000,000 daltons is 5% or greater; and (d) deactivating the enzyme.  

2. The method of claim 1 wherein the starch/enzyme slurry is treated such that the concentration of starch hydrolyzate product having a molecular weight greater than 1,000,000 daltons is 8% or greater.  

3. The method of claim 1 wherein the jet cooking is carried out at a 0 temperature greater than 212 F,.  

4. The method of claim 1 wherein gelatinization of the starch/enzyme slurry is completed in a plug flow continuous reactor.  

5. The method of claim 1 wherein treatment of the starch/enzyme slurry to achieve the selected degree of thinning is completed in a semibatch reactor.  

6. The method of claim 1 wherein the enzyme is deactivated by addition of a deactivating agent.  

7. The method of claim 1 wherein the enzyme is deactivated by subjecting the mixture to an elevated temperature sufficient to deactivate the enzyme.  

8. The method of claim 1 wherein the alphaamylase is a high temperature alphaamylase characterized by optimum activity at a temperature of from 0 0 92 C to 98 C.  

9. A stable enzymethinned derivatized starch dispersion characterized by a selected degree of thinning which is produced according to the method comprising the steps of : (a) combining a derivatized granular starch with an alphaamylase enzyme to form a starch/enzyme slurry ; (b) passing said starch/enzyme slurry through a jet cooker under conditions selected to gelatinize the starch; (c) treating the starch/enzyme slurry to complete gelatinization and achieve the selected degree of thinning such that the concentration of starch hydrolyzate product having a molecular weight greater than 1,000,000 daltons is 5% or greater; and (d) deactivating the enzyme.  

10. The starch dispersion of claim 9 wherein the starch/enzyme slurry is treated such that the concentration of starch hydrolyzate product having a molecular weight greater than 1,000,000 daltons is 8% or greater.  

11. The starch dispersion of claim 9 wherein the starch hydrolyzate products having a molecular weight of 1,000,000 daltons and less are characterized by a bimodal distribution when compared to the monomodal distribution of an exclusively acid thinned dispersion of identically derivatized starch which have been thinned to the same initial viscosity at the same solids wherein the enzyme thinned dispersion of the invention is characterized by having a relatively lower concentration of starch hydrolyzate products at the mode molecular weight of said corresponding acid thinned dispersion; and by a relatively greater concentration of starch hydrolyzate products in a molecular weight range greater than said mode and less than 1,000,000 daltons; and by a relatively greater concentration of starch hydrolyzate products in a molecular weight range less than said mode and greater than 0 daltons.  

12. The starch dispersion of claim 11 wherein the enzyme thinned dispersion of the invention is characterized by having a relatively lower concentration of starch hydrolyzate products in the molecular weight range of from 10,000 to 250,000 daltons; a relatively greater concentration of starch hydrolyzate products in the molecular weight range of from 250,000 daltons to 1,000,000 daltons; and a relatively greater concentration of starch hydrolyzate products in the molecular weight range of from 0 to 10,000 daltons when compared to said exclusively acid thinned dispersion of identically derivatized starch.  

13. The starch dispersion of claim 9 which is characterized by an as is solids content of greater than 40% by weight.  

14. The starch dispersion of claim 9 wherein said starch is ethylated.  

15. A starch dispersion according to claim 9 wherein the starch is a dual derivatized starch.  

16. The starch dispersion according to claim 15 wherein the starch is a propylated cationic starch.  

17. A wet end sizing composition comprising the starch dispersion of claim 15.  

18. The wet end sizing composition of claim 17 which further comprises a sizing agent selected from the group consisting of ASA (alkenyl succinic anhydride); AKD (alkyl ketene dimer); and rosin.  

19. A starch dispersion comprising the reaction product of the starch of claim 9 and one or more unsaturated monomers.  

20. The starch dispersion of claim 19 wherein. said unsaturated monomers are selected from the group consisting of styrene, 1,3butadiene, butyl acrylate, ethyl acrylate, methyl methacrylate, acrylic acid, methacrylic acid.  

21. The starch dispersion of claim 19 wherein said dispersion is characterized by an as is solids content of greater than 50% by weight.  

22. The starch dispersion of claim 19 wherein said dispersion is characterized by an as is solids content of greater than 60% by weight.  

23. A size press coating comprising the starch dispersion of claim 19 and a pigment.  

24. A coating color composition comprising the starch dispersion of claim 19 and a pigment.  

25. An adhesive composition comprising the starch dispersion of claim 19.  

26. A liquid laundry starch comprising the dual derivative starch composition of claim 15. 

Description

IMPROVED ENZYME THINNED STARCHES This application claims priority on provisional patent application Serial No. 

60/098,615 filed August 31,1998. 

BACKGROUND OF THE INVENTION The present invention relates to high solids, high molecular weight cooked starch dispersions and to the stability and molecular weight distribution of these high solids dispersions at a given solids and viscosity when cooked and thinned using the teachings presented herein. More specifically, the invention relates to the use of a jet cooker to gelatinize and promote the enzyme thinning of derivatized starches. 

It is well known in the art that stability of a cooked starch dispersion is related to the solids of the dispersion, the ratio of the amylose (linear) fraction to the amylopectin (branched) fraction of the starch molecules, the type and degree of substitution and the amount of depolymerization of the starch, particularly the amylose fraction. It is also known in the field of carbohydrate chemistry that the increase in the viscosity of cooked starch paste is a function of the alignment of the carbohydrate chains and the hydrogen bonding that occurs between adjacent hydroxyls on these chains. 

Anything that interferes with this alignment or the hydrogen bonding, will retard setback and the increase in viscosity that is normally seen as a cooked starch paste cools and ages. 

There are a number of ways that workers in the art have found over the years to interrupt the alignment and the hydrogen bonding (commonly referred to as retrogradation) between the starch chains. The first and most basic is to grow a starch producing plant (particularly corn), that produces a higher percentage of branched molecules characterized by a-1,6-bonds (amylopectin molecules). The more highly branched the molecules, the more difficulty they have in aligning and causing setback and increased viscosity. These high amylopectin starches are commonly called waxy starches. 

These starches are not as common as starch produced from normal dent corn because the corn plant that produces the waxy starches has to be kept separate from the rest of the corn crop and the plants that mill this corn must have a separate line to handle the waxy 

corn. Thus the waxy starches are much more expensive than starch from normal dent corn. 

Hofreiter et al., U. S. Patent No. 4,121,974 is said to disclose a method for enzymatically degrading the amylose portion of the cooked starchpaste without degrading the amylopectin to produce a starch which acts like a waxy starch in its ability to form retrogradation resistant starchpastes. Alternatively, starch is derivatized with chemicals to add substituents onto the starch chains to retard setback and retrogradation in cooked starch pastes. These substituents function to physically prevent the starch chains from getting close enough to each other to form hydrogen bonds. These substituted starches usually produce clear cooked dispersions that remain stable for short periods of time when the solids of the cooked paste are low (2-6%) and the cooked dispersion is kept hot (160- 210°F). A few of the more common compounds that are reacted with the starch in its granular state are ethylene oxide, propylene oxide, acetic anhydride, acrylonitrile, acrylamide, sodium monochloacetate and tertiary and quaternary amines. 

Brumm, U. S. Patent No. 5,612,202 relates to a two step process for thinning a starch and producing a low dextrose equivalent (DE) maltodextrin consisting of a first step of enzyme thinning the starch to a DE of from about 10 to 30. This is equivalent to a molecular weight of the branched (amylopectin) fraction of the starch of between 50,000 and 20,000 daltons and a low molecular weight (less than 5,000 daltons) linear fraction. Further, even when the first enzyme thinning step only functions to thin the starch to a DE of about 10 the concentration of the high molecular weight amylopectin fraction having a molecular weight greater than 1,000,000 daltons is less than 4% by weight. A stable low DE product is then produced by removing the low molecular weight amylose fraction to yield a molecular weight fraction with a molecular weight from about 20,000 to about 50,000 daltons, a concentration of from about 70% to about 100% and a D. E. between 2 and 8. Practice of the method of Brumm results in extensive degradation of the high molecular weight (greater than 1,000,000 daltons) amylopectin portion of the starch to levels of less than 4% by weight. 

Kightlinger et al., U. S. Patent No. 4,301,017 discloses methods for producing thinned, substituted starches that can be used to produce stable, high solids starch copolymer dispersions. According to Kightlinger, these thinned and derivatized 

starches should have degree of substitution of at least 0.05 and an intrinsic viscosity of not less than 0.12 deciliters per gram (dUg) to produce high solids starch graft copolymer dispersions that had sufficient strength for use in textiles and coatings. While these starches may be derivatized using a number of different reagents, Kightlinger specifically teaches that the best results are obtained with bulky and/or charged compounds. At high solids and these viscosities, Kightlinger showed that even when bulky substituents such as diethylaminoethyl chloride were used as the derivatizing agent, a minimum degree of substitution of about 0.06 was needed to give stability to the starch graft copolymers of his invention. Both acid and enzyme thinning of the derivatized starch are disclosed, with the examples teaching the method of enzyme thinning the starch using a low temperature alpha amylase in a batch process. 

Nguyen et al., U. S. Patent No. 5,003,022 discloses stable, high solids, starch copolymer dispersions characterized by improved strength at intrinsic viscosities lower than 0.12 dl/g. Because of these lower intrinsic viscosities, they were able to use lower levels of smaller substituents (such as ethylene oxide) on the starch at relatively low concentrations to produce these dispersions. 

To produce a high solids, low viscosity, cooked starch paste that is resistant to retrogradation and setback, the starch must not only be derivatized, the starch chains must also be shortened. This depolymerization or shortening of the starch chains is generally done in the granular state by the addition of acid to lower the pH of the starch slurry and hydrolyze the linkages between individual anhydroglucose units. This method generally works well but has definite disadvantages. One disadvantage is the range of viscosities of the commercial starches now produced using acid modification. Thus, the normal viscosity ranges for commercially available starches are quite wide. For example, the viscosity range for one typical industrial ethylated cornstarch for use in the size press of a paper machine in a paper mill is 400-1150 cp at 23% solids and 38°C. There thus remains a desire among end users of the starch that the viscosity range of the cooked paste at a given solids and temperature be narrower and more consistent from batch to batch. 

The second major disadvantage of acid modification is that it is performed at the starch producer and not at the mill. Because a large paper mill will generally need a number of different starches with different solids and viscosity requirements, mills must 

have storage for different starches at the mill. A size press starch is generally not the same viscosity and solids as a coating starch and size press and coating starches for different paper grades can also have different viscosity and solids requirements. If the mill does not want to store all of the different starches it needs for each use, it must compromise on the starches it purchases to reduce the number of different starches it must store. 

The third major disadvantage to acid modification relates to the loss of soluble starch that occurs as a result of the acid modification process. During the manufacturing process to make a thinned starch, the acid modification of the starch granule produces a certain amount of low molecular weight, soluble starch. This low molecular weight starch is subsequently lost during the washing and filtering of the granular product. These losses range from 0.5% for lightly thinned starches to up to 15% for highly thinned starches. If this starch has also been derivatized, the derivatization is generally done in the granular state before the acid modification. It is thus derivatized material that is lost during the acid modification. In addition, tests have shown that this soluble starch that is lost during acid modification contains a higher percentage of the derivatizing agent than the rest of the starch granule. Therefore, not only is acid modification costly because of the time and chemicals required to carry out the thinning, it is also costly because there a loss of material is the most highly substituted part of the granule and more of the derivatizing agent must be used to compensate for this loss. 

Accordingly, there remains a desire in the art for improved methods of producing thinned derivatized starches. 

SUMMARY OF THE INVENTION The present invention provides jet cooked, enzyme-thinned, derivatized starch dispersions and products made from these dispersions which are characterized by improved stability when compared to thinned derivatized starch dispersions made using conventional acid thinned or enzyme thinned or a combination of acid and enzyme thinning. In addition, the invention provides for uses for these improved products. 

Specifically, the invention provides a method of preparing a stable enzyme- thinned starch dispersion characterized by a selected degree of thinning comprising the steps of : (a) combining a derivatized granular starch with an alpha-amylase enzyme to 

form a starch/enzyme slurry; (b) passing said starch/enzyme slurry through a jet cooker under conditions selected to gelatinize the starch; (c) treating the starch/enzyme slurry to complete gelatinization and achieve the selected degree of thinning such that the concentration of starchhydrolyzate product having a molecular weight greater than 1,000,000 daltons is 5% or greater or more preferably 8% or greater ; and (d) deactivating the enzyme. Preferably, step (b) is carried out under conditions such that the alpha- amylase enzyme is not completely inactivated wherein the originally added enzyme can promote continued thinning of the starch. According to a preferred aspect of the invention the jet cooking is carried out at a temperature greater than 212°F with jet- cooking temperatures of about 235°F being particularly preferred. While it is generally desired that the starch component of the starch/enzyme slurry be substantially or completely gelatinized in the jet cooker the gelatinization of the starch/enzyme slurry may be completed in a plug flow continuous reactor. Moreover, such a plug flow reactor (also known as a hold column) functions to continue the enzyme hydrolysis of the derivatized starch that was initiated in the jet cooker. Hold times in the plug flow reactor can range from 10 seconds to up to 30 minutes but hold times ranging from 2 to 20 minutes are preferred with hold times of about 5 minutes being particularly preferred. According to a preferred aspect of the invention, the temperature of the plug flow reactor is held above 212°F with input and output temperatures of about 235°F being particularly preferred. 

In the place of or in addition to the use of a plug flow continuous reactor, the starch/enzyme slurry which has been treated in the jet cooker may be further treated to achieve the selected degree of thinning in a semi-batch reactor which can be a stirred reaction vessel. Such a vessel is preferably held at atmospheric pressure but may be heated or cooled in order to optimize the enzyme activity. The use of a semi-batch reactor differs from that of a plug flow reactor in which each quantity of starch/enzyme slurry is reacted for the same amount of time and under the same conditions. The combination of jet cooker and plug flow reactor thereby produces a thinned starch which has been uniformly treated. In contrast when the starch/enzyme slurry is introduced into the semi- batch reactor it is blended with starch and enzyme which has reacted in the reactor over a period of time and if the batch time is time t then the starch reacted in the semi-batch reactor for time t will have a different hydrolysis profile than that held for time'/2 t or 

where t = 0. Nevertheless, as one aspect of the invention, it is believed that improved properties are provided by treatment of the starch/enzyme slurry in a semi-batch reactor after it has been treated in the jet cooker. 

To produce the dispersions of the present invention, a slurry containing water, a derivatized starch and enzyme is passed through a jet cooker (hydroheater) and a short hold column. Depending on the length of the column, the mixture may be passed through a second jet cooker and the enzyme deactivated or the partially thinned pasted starch/enzyme mixture is collected in a stirred vessel. This pasted starch/enzyme mixture would then be collected over a period of time during which the starch would continue to thin in the stirred vessel. After a predetermined length of time, a deactivating agent (usually sodium hypochlorite) is added to the starch/enzyme mixture to deactivate the enzyme or the mixture can be passed through a second jet cooker at a much higher temperature to deactivate the enzyme. While it is preferred that the enzyme-thinned starches of the present invention be exclusively enzyme thinned, it is recognized that minor amounts of acid thinning will not fundamentally change the character of the resulting improved products. Accordingly, the term"enzyme-thinned"will not exclude light acid modification which does not result in greater than a 1% solids by weight soluble loss if the remaining thinning is carried out by enzymatic means. Further, while enzyme-thinning according to the invention is primarily by means of alpha-amylases additional thinning may be carried out by use of enzymes such as beta-amylases, glucoamylases, alpha- glucosidases, isoamylases, amylo-1,6-D-glucosidases, pullanases and the like. 

The present invention provides methods and products which avoid many of the limitations associated with the acid modification of starch. Specifically, the cooked starch paste is enzyme thinned instead of acid modifying the starch granule. By carrying out this step the low molecular weight material that is produced during the thinning step will remain with the cooked paste such that sewer losses of the soluble products are minimized. The only chemicals needed to enzymatically thin the starches are a small amount of enzyme and a small amount of calcium to stabilize the enzyme. 

The jet cooked, enzyme thinned, derivatized starch pastes of the invention may also be used as the starting material to manufacture starchcopolymer materials for use in the paper, textile and other industrial processes and products. These starch

copolymers not only need thinned derivatized products with specific viscosity ranges, they also need starches that will produce products with adequate strength and viscosity stability. 

While various alpha amylases may be used according to the invention it is particularly preferred according to one aspect of the invention that the alpha-amylase be a high temperature alpha-amylase in order that elevated temperatures may be used in the jet cooker and any subsequent reactors. A particularly preferred high temperature alpha- amylase is derived from a modified strain of Bacillus licheilifornlis and is characterized by optimum activity at a temperature of from 92°C to 98 °C. One preferred such alpha- amylase for use according to the invention is Spezyme AAL (Genencor International, Rochester, NY). After completion of gelatinization and thinning of the starch to a desired level the enzyme is deactivated by means including addition of a deactivating agent such as sodium hypochlorite or by subjecting the mixture to an elevated temperature sufficient to deactivate the enzyme. 

It has thus been discovered that by using a jet cooker to cook the starch/enzyme slurry, a thinned, derivatized, high solids, high molecular weight, high strength, cooked starch paste can be produced that is much more stable than pastes produced by conventional means using either acid or enzyme. It has further been discovered that when a derivatized starch is treated according to the methods of the invention, high solids, high molecular weight stable starch dispersions can be produced that leave a substantial portion of the high molecular weight fraction (greater than 1,000,000 daltons) intact. As one aspect of the invention, it is recognized that maintenance of the high molecular weight (greater than 1,000,000 daltons) amylopectin fraction of the starch hydrolyzate at levels greater than 5% and more preferably greater than 8% by weight provides improved strength and other properties to the enzyme-thinned products of the invention. 

The improved dispersions of the invention can be produced even if the starch is derivatized with a relatively low level of a small molecule. These stable, high solids cooked starch pastes have applications in a number of different areas. The invention also provides size press coatings, coating color compositions, concrete additives and adhesive compositions comprising the starch dispersions of the invention. The stable, 

high solids, cooked pastes are particularly useful as size press starches on a paper machine. This is especially true for mills that require high solids low viscosity pastes, but would like the higher strength associated with a less thinned, higher viscosity, lower solids product. 

The dispersions of the invention are useful in the manufacture of high solids starch copolymer dispersions that exhibit almost no increase in viscosity over time, particularly when compared to dispersions that are made with similar starches that are not thinned using the methods of this invention. These stable, high solids, cooked pastes are also useful in the manufacture of a high solids, dual derivative starch paste used in the emulsification of sizing compounds for the wet end of a paper machine. These pastes are particularly useful when shipped to the mill as precooked, ready to use dispersions, eliminating the need for cooking equipment at the mill. These dual derivative dispersions can contain an emulsified sizing compound such as AKD or other novel sizing compounds, or they can be shipped to the mill without the sizing agent and used at the mill to emulsify the sizing agents. Emulsification at the mill is particularly important for sizing agents such as ASA that are more sensitive to hydrolysis. 

BRIEF DESCRIPTION OF THE FIGURE Fig. 1 is a graph which depicts the molecular weight distribution of an enzyme-thinned derivatized starch of the invention compared with an acid-thinned derivatized starch which has been thinned to approximately the same initial viscosity at similar solids. 

DETAILED DESCRIPTION The invention provides improved thinning methods and compositions comprising using a jet cooker and auxiliary equipment to cook and thin an enzyme containing, derivatized starch slurry, especially starches derivatized with smaller, less costly and easier to use reagents. 

As will be discussed in further detail later, the starch dispersions of the present invention differ from those produced by acid modification or the combination of 

acid and enzyme hydrolysis with respect to the distribution of starch hydrolyzate products having molecular weights of less than 1,000,000 daltons. 

Native starches contain both amylopectin and amylose molecules. depending on the origin of the starch, the relative amount of amylopectin to amylose will vary from almost 100% (as in waxy corn starch), to less than 20% (as in high amylose corn starch). The typical ratio of amylopectin to amylose in native starches is about 80% amylopectin to about 20% amylose. When modern analytical gel permeation chromatography (GPC) HPLC is used to separate the starch, the large, highly branched molecules appear first and the shorter more linear molecules appear last. As these starches are thinned, the distribution of starch molecular weights takes on a pronounced bimodal distribution. The large, highly branched molecules appear as a group of peaks at molecular weights of greater than about 1,000,000 daltons and the shorter, more linear molecules show up as a peak or peaks at molecular weights of less than 1,000,000 daltons. The relative amounts of the starch hydrolyzate products represented by these peaks have been found to be important when comparing the products of the present invention with those of either acid modified starches or starches which have been thinned using a combination of acid and enzyme hydrolysis. 

When acid alone is used to thin a starch, the distribution of starch hydrolyzate molecules of molecular weight less than 1,000,000 daltons generally ranges from about 250,000 to about 5000 daltons, is monomodal and is represented by a single peak when depicted on a plot with the x-axis representing starch molecular weight and the y-axis depicting relative concentrations. For example, Fig. 1 depicts the molecular weight distributions of an enzyme-thinned derivatized starch according to the invention (which is the enzyme thinned starch of Example 5) and an acid modified derivatized starch equivalent to that produced in comparative Example 6 which have been thinned to approximately the same initial viscosity at the same solids. In comparison to the monomodal distribution of the acid-thinned starch hydrolysis products, the enzyme- thinned derivatized starch according to the invention is characterized by having a molecular weight of 1,000,000 daltons and less which is characterized by a bimodal distribution wherein the enzyme thinned dispersion of the invention is characterized by having a relatively lower concentration of starch hydrolyzate products at the mode 

molecular weight of said corresponding acid thinned dispersion (which is represented by the peak between 0 and 1,000,000 daltons on the plot of the acid-thinned material in Fig. 

1); and by a relatively greater concentration of starch hydrolyzate products in a molecular weight range greater than said mode and less than 1,000,000 daltons; and by a relatively greater concentration of starch hydrolyzate products in a molecular weight range less than said mode and greater than 0 daltons. 

By way of illustration with respect to the thinned starches characterized in Fig. 1 which have been thinned to approximately the same initial viscosity at similar solids; the enzyme thinned dispersion of the invention is characterized by having a relatively lower concentration of starchhydrolyzate products in the molecular weight range of from 10,000 to 250,000 daltons; a relatively greater concentration of starch hydrolyzate products in the molecular weight range of from 250,000 daltons to 1,000,000 daltons; and a relatively greater concentration of starch hydrolyzate products in the molecular weight range of from 0 to 10,000 daltons when compared to said exclusively acid thinned dispersion of identically derivatized starch. Thus, the products of the present invention are characterized by relatively more of short linear hydrolyzate products having molecular weights of less than 10,000 daltons than result from an equivalent degree of acid hydrolysis but relatively fewer linear hydrolyzate products having molecular weights between 10,000 daltons and 50,000 daltons than from acid hydrolysis. Further, the products of the present invention comprise relatively more"amylose-like"starch hydrolyzate products having molecular weights between 50,000 daltons and 1,000,000 daltons which products are primarily linear but comprise short 1,6- branches many of which were not cleaved by the alpha amylase. While not intending to be bound by any theory of their invention, it is believed that the higher concentration of hydrolyzate products having molecular weights between 250,000 daltons and 1,000,000 daltons provide increased strength to the products of the invention while the relatively increased levels of lower molecular weight hydrolyzate products having molecular weights of less than 10,000 daltons provide increased stability to the products of the invention. Further, relatively reduced levels of primarily linear hydrolyzate products having molecular weights between 10,000 and 250,000 daltons reduces the tendency of linear amylose-like molecules to hydrogen-bond and promote retrogradation. 

Because the degree of thinning affects the average molecular weight of the starch in each peak, those of ordinary skill in the art will recognize that this comparison is only descriptive when comparing the enzyme-thinned starches of the invention to an acid thinned starch standard which has been thinned to the same initial viscosity at the same solids. Thus, a highly thinned, low solids acid modified starch cannot readily be compared to a lightly thinned, high solids enzyme-thinned starch. 

Thus, the starch dispersions of the present invention are characterized by improved stability and functional properties wherein dispersions comprising the enzyme thinned starches may be used at higher solids levels while maintaining their stability. Thus, the invention provides dispersions characterized by an as is solids content of greater than 30% and more preferably 40% by weight. 

Preferred starches include corn, potato, wheat, rice, tapioca and the like, with corn, potato and tapioca being especially preferred. The preferred derivatizing agents are ethylene oxide, propylene oxide, acetic anhydride, acrylonitrile, acrylamide, sodium monochloroacetate, tertiary and quaternary amines and combinations of these reagents. 

The derivatized starches of the invention may be substituted with a variety of moieties known to the art. Suitable functional derivative groups include alkyl, alkenyl, aryl, arylalkyl, arylalkenyl, cycloalkyl, and cycloalkenyl ethers, hydroxyethers, esters including organic acid esters, amides, ketones, acetals, and ketals, and derivatives thereof, carboxylates, phosphates, sulfates, sulfonates, amino, and quaternary ammonium groups, and combinations thereof. Preferred derivative groups include benzyl, allyl, hydroxyethyl, hydroxypropyl, hydroxybutyl, and 2- hydroxy-3-butenyl ethers, formate, acetate, propionate, butyrate, dodecanoate, and stearate esters, alkenyl succinate esters, carboxylic acid, carboxymethyl, and carboxyethyl derivatives, and combinations thereof. A particularly preferred starch is hydroxyethyl starch. Especially preferred for starchsubstitution in the practice of the present invention are ethylene oxide, propylene oxide, quaternary amines and combinations of these reagents. While other reagents will work equally as well in the practice of this invention, ethylene oxide, propylene oxide and the quaternary amines are 

especially preferred because of their low cost on a mole basis and their relative ease of reactivity with granular starch in an aqueous system. 

While the degree of substitution is very important when producing a stable high solids starch dispersion, the degree of substitution will vary with the type of starch, the type of substituent, the solids of the end product and the degree of depolymerization. 

It is the higher degree of stability seen through the practice of the present invention (jet cooking the enzyme/starch slurry) that allows the use of smaller, less costly reagents to produce high solids, high strength and sometimes high viscosity, stable thinned starch pastes and starchcopolymer dispersions made from these pastes. 

According to one aspect of the invention, the starch is a dual derivatized starch with dual derivative starches comprising the combination of cationic and nonionic moieties being preferred. Preferred nonionic moieties according to the invention are hydroxyalkyl moieties with preferred cationic moieties being tertiary and quarternary amine compounds with tertiary and quarternary substituted ammonium compounds being preferred. A particularly useful dual derivatized starch according to this aspect of the invention is propylated cationic starch. 

The dual derivative products of the invention are useful for a variety of purposes including but not limited to use as a component of a wet end sizing composition. 

Such wet end sizing compositions further comprise a sizing agent selected from the group consisting of ASA (alkenyl succinic anhydride), AKD (alkyl ketene dimer) and rosin. 

Such dual derivative starches are also particularly useful as binder components of improved liquid laundry starches. 

The products of the invention may also be used as components of blends with synthetic polymers or as reaction products with one or more unsaturated monomers according to methods such as those of Nguyen et al., U. S. Patent No. 5,003,022 and Nguyen et al., U. S. Patent No. 5,416,181. Unsaturated monomers for reaction with starches can include, but are not limited to, styrene, p-methylstyrene, p-t-butylstyrene, p-methoxystyrene, vinyl toluene, vinyl naphthalene, and divinyl benzene; isobutylene, 4-methyl-1-pentene, 1,3-butadiene, 2-methyl-1,3-butadiene, 1,4-hexadiene, and 5- ethylidene-2-norbornene; acrylic acid, methacrylic acid, itaconic acid, and their C, to Cl8 alkyl, cycloalkyl, alkenyl, aryl, arylalkyl, and arylalkenyl esters; methyl acrylate, 

ethyl acrylate, n-butyl acrylate, i-butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, i-butyl methacrylate, isobornyl methacrylate, phenyl methacrylate, lauryl methacrylate, behenyl ethoxyl methacrylate, ethylene glycol diacrylate and ethylene glycol dimethacrylate; the Cl to Cl, alkyl esters of maleic and fumaric acids; acrylonitrile; vinyl acetate, vinyl butyrate, vinyl stearate, and sodium vinyl sulfonate; methyl vinyl ether, ethyl vinyl ether, and i-butyl vinyl ether; methyl vinyl ketone; acrylamide, N-methylacrylamide, N, N-dimethylacrylamide, N-t- butylacrylamide, N-t-octylacrylamide, and N-methylolacrylamide, methacrylamidoethylethyleneurea, vinyl chloride, vinylidene chloride, vinyltrimethylsilane, m-isopropylidene-dimethylbenzyl isocyanate, and the like, and mixtures thereof with the unsaturated monomers selected from the group consisting of styrene, 1,3-butadiene, butyl acrylate, ethyl acrylate, methyl methacrylate, acrylic acid, and methacrylic acid being particularly preferred. Starch copolymer compositions comprising blends or the reaction products of the enzyme thinned derivatized starches of the invention are characterized by improved stability at elevated solids levels. According to one aspect of the invention dispersions are provided characterized by an as is solids content of greater than 30% by weight and more preferably having as is solids content of greater than 40%, 50% and 60% by weight. 

EXAMPLE 1 According to this example, a stable high viscosity 30% solids dispersion comprising an enzyme thinned dual derivative starch was prepared according to the methods of the present invention. Specifically, a potato starch derivatized with both propylene oxide and a quarternary amine was thinned through a jet cooker using a high temperature enzyme. Specifically, 750 pounds ds basis native potato starch (Penford Products Co., Cedar Rapids, IA) was reacted with propylene oxide. and (3-chloro-2- hydroxypropyl) trimethylammonium chloride to produce a dual derivative potato starch containing about 2.1% by weight hydroxypropyl substitution and 0.37% by weight nitrogen equivalent to a total degree of substitution of about 0.11. This starch was washed and reslurried in water to a Be'Tc of 18.3 which was equivalent to about 32.5% solids ds basis. The temperature of the slurry was about 84°F and the pH was about 6.8. 

To this slurry was added 125 g CaC-2 HO (123 ppm Ca++) and 119.1 g (0.035% by weight based on ds starch) alpha amylase (Spezyme AA-L Heat Stable Alpha-Amylase, Genencor International) with an activity of 5650 TAU/g. (One TAU is defined as the quantity of enzyme that will dextrinize one milligram of starch per minute at a pH 6.6 and 30°C under specific assay conditions.) A fixed displacement pump was used to pump the slurry through a jet cooker at a rate of 4.7 gallon/min. at 235-240°F cooked paste temperature measured in line just after the cooked paste had passed through the jet cooker. The starch paste was cooked through a 4"diameter by 10'hold column (plug flow/continuous reactor) into a 1000 gallon stirred semi-batch reactor. Starch was cooked into the reactor for a total of about 50 minutes. At this time, about 2100 ml of 16% sodium hypochlorite was added to deactivate the enzyme. A sample was taken and analyzed according to the procedures described below. 

Rapid Visco Analyzer Test Method This test method utilizes the Rapid Visco Analyzer (RVA) to analyze starch samples during a starch cook and thinning. The Newport RVA Series 4 instrument (Newport Scientific Pty., 1/2 Apollo Street, Warriewood NSW 2102, Australia) has made possible the development of specific time and temperature dependent viscosity profiles indicative of various levels of enzymatic hydrolysis. This method can provide a quick and relatively simple comparison to known products that have been enzymatically hydrolyzed using the same or similar thinning methods. 

Procedure: (1) 30 g of hot cooked starch paste is added to the RVA cup and placed in the instrument; (2) the instrument is set to mix the sample at 600 rpm; (3) a program is used to cool down and hold the sample at 40°C and 20°C for a length of time sufficient to obtain a stable viscosity reading at each temperature; (4) these viscosity profiles can then be used to follow the degree of depolymerization during the enzyme thinning of a cooked starch paste by comparing them to the thinning profiles of known starches. This technique works because it has been found that a given type of substituted starch at a given temperature will thin to the same viscosity over the same time interval if the same concentration of starch and enzyme are used. 

Viscosity for the enzyme-thinned starch using the RVA at the above conditions was initially 975 cp and 1132 cp after storage of the starch at 23 °C for 2 months. 

Size Exclusion Chromatography of Aqueous Starch Suspensions Size exclusion chromatography of starch dispersions in water can allow one skilled in the art to infer about the approximate molecular weight distributions of amylose and amylopectin in the cooked starch suspension. A calibration curve using water-soluble pullulans of known molecular weight was prepared using Shodex P-82 Standards (distributed by Phenomenex Inc., 2320 W. 205th Street, Torrance, CA, 90501 U. S. A.) chromatographed through a Waters Ultrahydrogel Linear column. Using the refractive index response of the material in solution, a relatively linear fit between the log of the standard's molecular weight and its elution time can be established. The change in the low molecular weight amylose fraction of the hydrolyzed starch suspension between 1,000 and 1,000,000 MW is of most interest in this particular application, while some additional information can be acquired from the higher molecular weight amylopectin fraction. 

% dp>7 Determination using Resin-Based Column HPLC An additional method that has been historically used to determine the amount of hydrolysis of a starch product is similar to the SEC method described previously but somewhat less sensitive to large molecular weight fractions. The separation of water-soluble carbohydrates with a Bio-Rad Aminex HPX-42A Silver Ion based column (Bio-Rad Laboratories 2000 Alfred Nobel Drive, Hercules, CA 94547) gives an indication of the degree of polymerization or dp of the starch chain. A dp=l is equivalent to one glucose unit, whereas a dp=10 would equate to a polymer 10 glucose units in length. The unit of convention describing this particular invention is % dp>7 or all chain lengths equal to or greater than 7 glucose units present in the molecular weight distribution. 

Examples 2-6 set out below illustrate the use of stable, high solids, derivatized, cooked starch dispersions of the invention to produce starchcopolymers. 

Examples 2 and 3 illustrate the use of these dispersions to produce 50% solids starch

copolymers and Example 5 illustrates the use of these dispersions to produce a 30% dispersion. Examples 4 and 6 are acid modified controls for Examples 2,3 and 5. 

EXAMPLE 2 According to this example, an enzyme-thinned starch according to the invention was used to produce a styrene/butadiene starchcopolymer. In this example, an ethylene oxide derivatized cornstarch is enzyme thinned and reacted with styrene and butadiene to produce a 50% solids starch grafted copolymer for use as a binder in paper applications. Specifically, 1597 pounds ds (dry substance basis) ethylated cornstarch (Penford Gum 300, Penford Products Co.) (2.69% by weight ethylene oxide substitution) with a degree of substitution of 0.098 was slurried in water to a Be'Tc of 19.8 which was equivalent to about 35.2% solids ds basis. The temperature of the slurry was about 80°F and the pH was about 6.3. To this slurry was added 268 g CaCI2 2 H2O (100 ppm Ca++) and 580 g (0.080% by weight based on ds starch) alpha amylase (Spezyme t AA-L Heat Stable Alpha-Amylase, Genencor International) with an activity of 5650 TAU/g. A fixed displacement pump was used to pump the slurry through a jet cooker at a rate of 5.9 gallon/min. at about 235 °F cooked paste temperature measured in line just after the cooked paste had passed through the jet cooker. The starch paste was then cooked through a 4"diameter by 10'hold column (plug flow continuous reactor) with a hold time of about 1.5 minutes, into a 1,000 gallon stirred reactor. Starch was cooked into the reactor for a total of about 80 minutes. 

Samples were taken and analyzed at ten minute intervals starting at 90 minutes after the start of the cook according to the following procedure: A 300 gram sample was collected at each interval and the enzyme deactivated with about 0.5 g of 16% sodium hypochlorite and analyzed according to the RVA procedure described previously. 

When the proper degree of thinning had been obtained, about 4.5 liters of 16% sodium hypochlorite was added to deactivate the enzyme. The final thinned paste had a 40 °F RVA viscosity of 102 cp. 

The enzyme-thinned starch was cooled down to about 120°F and about 40 pounds of sodium persulfate was added to the stirring cooked paste. The agitator was stopped and about 870 pounds of styrene and 623 pounds of butadiene were added. The 

agitator was restarted and the mixture was heated to about 158°F and reacted for about 7 hours. The reactor was vented and 12 pounds of sodium persulfate was added. The mixture was allowed to react about 5 more hours and the pH was adjusted to about 6.2 with a combination of sodium hydroxide and sodium carbonate. About 1.5 liters of Kathon LX was added as a biocide. 

The enzyme-thinned starch copolymer composition of the invention was used as a binder in a coating color composition to coat paper. Specifically, a coating color composition comprising the components of Table I was produced according to the following method. 

Table 1 Composition Parts #1 Kaolin Clay (Premier) 80 Ground Calcium Carbonate (Carbitol 90) 20 StarchCopolymer 16 Lubricant (Nopcoat C-104). 4 Thickener, as needed (Polyphobe 206) 0-0.3 pH 8.5 Solids 58% The coating color composition was prepared by first adjusting the pH of the starch copolymer to 5.0-6.5. The starch copolymer was then added to the predispersed clay slip consisting of a 71% solids mixture of 80 parts #1 Kaolin clay (Premier, ECC International) and 20 parts ground calcium carbonate (Carbitol 90, ECC International). The lubricant (Nopcoat C-104, Henkel) was added to the clay/starch copolymer mixture. Thickener (Polyphobe 206, Dow Chemical) was added while the pH is maintained at 8.0-8.5 until a Brookfield viscosity of 1200-1400 cp (#4 Spindle, 100 rpm, 75 °F) has been reached. At this time, the coating color viscosity was measured over a 5 minute period to determine the delta viscosity. A two minute water release at 15 psi was then determined using a gravimetric water release meter (Kaltech). The coating compositions were then applied to a 35 pounds/3300 sq. ft. wood free paper sheet at a target coat weight of 8.5 pounds/3300 sq. ft. on one side only using a CLC (Cylindrical 

Lab Coater, Sensor and Simulation) coater. The CIS paper strips were then super calendered (Model 754 laboratory super calendar, Beloit Wheeler) through a Supertex (k top roll on steel bottom roll for a total of 3 nips (40 ft./min., gage nip pressure=550 psi and a steel roll temperature of 150°F). 

The resulting lightweight coated paper was then evaluated according to conventional methods with the results set out in Table 2 below. 

EXAMPLE 3 According to this example, an enzyme-thinned starch according to. the invention was used to produce a styrene/butadiene starchcopolymer. In this example, an ethylene oxide derivatized cornstarch was enzyme thinned and reacted with styrene and butadiene to produce a 50% solids starch grafted copolymer for use as a binder in paper applications. Specifically, 1597 pounds ds ethylated cornstarch (Penford Gum 300, Penford Products Co.) (2.69% by weight ethylene oxide substitution) with a degree of substitution of 0.098 was slurried in water to a Be'Tc of 19.8 which was equivalent to about 35.2% solids ds basis. The temperature of the slurry was about 92°F and the pH was about 6.2. To this slurry was added 268 g CaCI2 2 H2O (100 ppm Ca++) and 578 g (0.080% by weight based on ds starch) alpha amylase (Spezyme AA-L Heat Stable Alpha-Amylase, Genencor International) with an activity of 5650 TAU/g. A fixed displacement pump was used to pump the slurry through a jet cooker at a rate of 5.9 gallon/min. at about 235 °F cooked paste temperature measured in line just after the cooked paste had passed through the jet cooker. The starch paste was cooked through a 4"diameter by 10'hold column with a hold time of about 1.5 minutes, into a 1,000 gallon stirred reactor. Starch was cooked into the reactor for a total of about 78 minutes. 

The starch continued to thin for an additional 131 minutes. 

Samples were taken and analyzed at ten minute intervals starting at 90 minutes after the start of the cook according to the following procedure. A 300 g sample was collected at each interval and the enzyme deactivated with about 0.5 g of 16% sodium hypochlorite and analyzed according to the RVA procedure described previously. After 209 total minutes from the start of the cook, the proper degree of thinning had been obtained and about 4.5 liters of 16% sodium hypochlorite was added to deactivate the 

enzyme. The final thinned paste had a 40 °F RVA viscosity of 104 cp. The starch was cooled down to about 120°F and about 40.2 pounds of sodium persulfate was added to the stirring cooked paste. The agitator was stopped and about 888 pounds of styrene and 636 pounds of butadiene were added. The agitator was restarted and the mixture was heated to about 158°F and reacted for about 6.5 hours. The reactor was vented and 12 pounds of sodium persulfate was added. The mixture was allowed to react about 5 more hours and the pH was adjusted to about 6.6 with a combination of sodium hydroxide and sodium carbonate. About 1.5 liters of Kathon LX was added as a biocide. 

The enzyme-thinned starch copolymer product of the invention was then used as the binder component of a paper coating color composition to produce a lightweight coated paper according to the method of Example 2. The results of testing that coated paper are set out in Table 2 below. 

EXAMPLE 4 This comparative example illustrates the preparation of a starch copolymer control using a highly acid modified and enzyme thinned ethylated starch. In this example, an ethylene oxide derivatized cornstarch is reacted with styrene and butadiene to produce a 50% solids starchgrafted copolymer for use as a binder in paper applications. 

Specifically, 1570 pounds ds ethylated acid thinned cornstarch (Pen-cote starch, Penford Products Co.) (about 2.0% by weight ethylene oxide substitution) with a degree of substitution of about 0.075 was slurried in water to a Bue',., of 19.8 which was equivalent to about 35.2% solids ds basis. The temperature of the slurry was about 94°F and the pH was about 6.5. A fixed displacement pump was used to pump the slurry through a jet cooker at a rate of 5.9 gallon/min. at about 235°F cooked paste temperature measured in line just after the cooked paste had passed through a jet cooker. The starch paste was cooked through a 4"diameter by 10'hold column into a 1,000 gallon stirred reactor. 

Starch was cooked into the reactor for a total of about 81.5 minutes. The starch was cooled down to about 187°F. At this time, 118 mi of alpha amylase (Validase BAA 1200L, Valley Research) was added to the stirred cooked paste. The starch was thinned to an RVA viscosity of 104 cp at 40°C. At this time, about 4.4 liters of 16% sodium hypochlorite was added to the thinned starch to deactivate the enzyme. 

The starch was cooled down to 120°F and about 39 pounds of sodium persulfate was added to the stirring cooked paste comprising the acid modified and enzyme-thinned starch which was characterized by the same initial viscosity at the same solids as the enzyme-thinned starches of the invention of Examples 2 and 3. The agitator was stopped and about 870 pounds of styrene and 623 pounds of butadiene were added. 

The agitator was restarted and the mixture was heated to about 158°F and reacted for about 7.0 hours. The reactor was vented and 11.8 pounds of sodium persulfate was added. The mixture was allowed to react about 5 more hours and the pH was adjusted to about 4.8 with a combination of sodium hydroxide and sodium carbonate. About 1.5 liters of Kathon LX (Rohm and Haas) was added as a biocide. 

The acid modified and enzyme-thinned starch copolymer product of the invention was then used as the binder component of a paper coating color composition to produce a lightweight coated paper according to the method of Example 2. The results of testing that coated paper are set out in Table 2 below. 

EXAMPLE 5 According to this example, an enzyme-thinned starch according to the invention was used to produce a starch copolymer. In this example, an ethylene oxide derivatized cornstarch was enzyme thinned and reacted with styrene and butadiene to produce a 30% solids starchgrafted copolymer for use as a binder in paper applications. 

Specifically, 10629 pounds ds ethylated cornstarch (Penford Gum 300, Penford Products Co.) (2.69% by weight ethylene oxide substitution) with a degree of substitution of 0.098 was slurried in water to a Be'Tc of 15.3 which was equivalent to about 27.2% solids ds basis. The temperature of the slurry was about 100°F and the pH was about 6.7. To this slurry was added 1772 g CaCI2 2 H2O (100 ppm Cl--) and 1205 g (0.025% by weight based on ds starch) alpha amylase (Spezyme AA-L Heat Stable Alpha-Amylase, Genencor International) with an activity of 5650 TAU/g. A fixed displacement pump was used to pump the slurry through a jet cooker at a rate of 64 gallon/min. at about 235 °F cooked paste temperature measured in line just after the cooked paste had passed through the jet cooker. The starch paste was cooked through a 12"diameter by 13'hold column with a back-pressure regulator to maintain a back pressure of about 50 psi and with a hold 

time of about 1 minute, into a 10,000 gallon stirred reactor. Starch was cooked into the reactor for a total of about 65.5 minutes. Two 750 g samples were collected at ten minute intervals starting at 90 minutes after the start of the cook. The enzyme was deactivated in each sample with about 1 g of 16% sodium hypochlorite. Each sample was then analyzed according to the RVA procedure described above. When the desired degree of thinning was reached, about 38 liters of 16% sodium hypochlorite was added to deactivate the enzyme. The final 40°C RVA viscosity was 186 cp. 

The enzyme-thinned starch paste was diluted to about 19.9% solids with water and cooled down to about 120°F. About 150 pounds of sodium bicarbonate and about 330 pounds of potassium persulfate were added to the stirring cooked paste. The agitator was stopped and about 4772 pounds of styrene and 3266 pounds of butadiene were added. The agitator was restarted and the mixture was heated to about 160°F and reacted for about 5.5 hours. The reactor was vented and 50 pounds sodium bicarbonate and 110 pounds of potassium persulfate were added. The mixture was allowed to react about 5 more hours. The final pH was about 5.5. About 15 liters of Kathon LX (Rohm and Haas) was added as a biocide. Brookfield viscosity of the starch copolymer measured using a Brookfield #4 spindle at 100 rpm and 23 °C was 78 cp and after 6 days at 6°C, was 128 cp at 6°C. 

The enzyme-thinned starch copolymer product of the invention was then used as the binder component of a paper coating color composition to produce a lightweight coated paper according to the method of Example 2. The results of testing that coated paper are set out in Table 2 below. 

EXAMPLE 6 This comparative example illustrates the preparation of a starch copolymer control using a highly acid modified and enzyme-thinned ethylated starch. In this example, an ethylene oxide derivatized cornstarch was reacted with styrene and butadiene to produce a starch grafted copolymer for use as a binder in paper applications. Specifically, 10,261 pounds ds ethylated acid-thinned cornstarch (Pen-cote starch, Penford Products Co.) (about 2.0% by weight ethylene oxide substitution) with a degree of substitution of about 0.075 was slurried in water to a Bue\, of 11.9 which was equivalent to about 20.0% 

solids ds basis. The temperature of the slurry was about 104°F and the pH was about 6.5. 

A fixed displacement pump was used to pump the slurry through a jet cooker at a rate of 64 gallons/min. at about 235°F cooked pasted temperature measured in line just after the cooked paste had passed through the jet cooker. The starch paste was cooked through a 12"diameter by 13'hold column into a 10,000 gallon stirred reactor. Starch was cooked into the reactor for a total of about 81 minutes. The starch was cooled down to about 120°F. About 150 pounds of sodium bicarbonate and about 330 pounds of potassium persulfate were added to the stirring cooked paste. The agitator was stopped and about 4309 pounds of styrene and 3078 pounds of butadiene were added. The agitator was restarted and the mixture was heated to about 160 °F and reacted for about 5.5 hours. The reactor was vented and 50 pounds sodium bicarbonate and 110 pounds of potassium persulfate were added. The mixture was allowed to react about 5 more hours and the pH was adjusted to about 4.8 with sodium carbonate and about 15 liters of Kathon LX (Rohm and Haas) was added as a biocide. Brookfield viscosity of the starch copolymer measured using a Brookfield #4 spindle at 100 rpm and 23 °C was 552 cp and after 6 days at 6°C, was 1376 cp at 6°C. 

The acid-thinned starch copolymer product of the invention was then used as the binder component of a paper coating color composition to produce a lightweight coated paper according to the method of Example 2. The results of testing that coated paper are set out in Table 2 below which reports the average results of sixteen experimental runs. 

Table 2 Example 2 3 4 5 6(A Initiator NaP NaP NaP KP KP Thinning-Type Enzyme Enzyme Acid Enzyme Aci@ Starch EO, % 2.7 2.7 2.0 2.7 1.8- % > dp=7 88.51 89.25 93.8 98.7 99.9 monomers/starch 50/50 50/50 50/50 42/58 42/5 styrene/butadiene 60/40 60/40 60/40 58/42 58/4 peak in-process viscosity, cP 670 770 700 --- --- % dry solids 48.4 50 47.0 30 30 Water Release 201 241 194 166 167 Brookfield Viscosity, cP 1020 430 1070 520 102@ Thickener 0.16 0.23 0.07 0.19 0.16 Final Coating Viscosity, cP 1210 1215 1200 1170 131@ Delta Viscosity 750 1140 1000 1620195@ HHSV, cP 52.3 67.3 57.0 58.4 49.9 75° Gloss 68.6 67.8 69.3 62.4 60.2 Roughness, PPS78 1.00 1.01 0.99 1.06 1.18 Brightness, % 77.8 78.6 78.0 78.7 78.@ Table 2 Example 2 3 4 5 6(A Opacity, % 84.6 85.6 84.9 84.9 85.@ Gurley porosity, sec/10 cc 136 123 166 136 127Stiffness, MD 46 53 49 47 48 Stiffness, XMD 28 29 29 24 28 IGT Pick, N/m 20.8 25.8 22.1 22.9 22.7 Passes to Failure 5/5 5/5 5/6 6 5.7 Force, g/cm 582/591 597/585 608/597 614 619 Slope, g/cmxsec 5.9/6.0 6.9/6.3 5.0/6.3 5.3 6 

EXAMPLE 7 This example illustrates the preparation of an enzyme thinned ethylated cornstarch using a jet cooker according to the teachings of the present invention. In this example, a low degree of substitution of about 0.038 (1.0% by wt. ethylene oxide substitution based on ds starch) ethylated cornstarch was thinned through a jet cooker with a high temperature alpha amylase. Specifically, 974 Ibs. ds (dry substance) basis ethylated cornstarch (Penford Gum 200, Penford Products Co., Cedar Rapids, IA) was slurried in water to a Bue', of 19.2 which is equivalent to about 34.1 % solids ds basis. 

The temperature of the slurry was about 100°F and the pH was about 6.4. To this slurry was added 164g CaCl2 2 H2O (100 ppm Ca++) and 141.4 g (0.032% by wt. based on ds starch) alpha amylase (Spezyme AA-L Heat Stable Alpha-Amylase, Genencor International) with an activity of 5650 TAU/g. (One TAU is defined as the quantity of enzyme that will dextrinize one milligram of starch per minute a pH 6.6 and 30°C under specific assay conditions.) A fixed displacement pump was used to pump the slurry through a jet cooker at a rate of 4.3 gal./min. at 235°F cooked paste temperature measured in line just after the cooked paste had passed through the jet cooker. The starch paste was cooked through a 4"hold column that held approximately 2 min worth of cooked paste and into a 1000 gallon stirred reactor. Starch was cooked into the reactor for a total of 70 minutes, but starch samples were taken every 5 minutes starting at 40 up to 80 minutes total thinning time. Two 750 g samples were collected at each interval and the enzyme deactivated with about 1 g of 16% sodium hypochlorite for each sample and analyzed according to the procedures described in Example 1. 

EXAMPLE 8 This example illustrates the preparation of an enzyme thinned ethylated cornstarch using a jet cooker according to the teachings of the present invention. In this example, a low degree of substitution, 0.038 (1.0% by wt. ethylene oxide substitution based ds starch), ethylated cornstarch was thinned through a jet cooker at between 190 and 200°F with a low temperature alpha amylase. Specifically, 776 Ibs. ds (dry substance) basis ethylated cornstarch (Penford Gum 200, Penford Products Co., Cedar Rapids, IA) was slurried in water to a Be'Tc of 19.2 which is equivalent to about 34.1 % solids ds basis. 

The temperature of the slurry was about 93 °F and the pH was about 6.7. To this slurry was added 131 g CaCl2 2 H2O (100 ppm Ca++ based on ds starch) and 70.4 g (0.02 % by wt. based on ds starch) alpha amylase (Validase BAA 1200L, Valley Research) with an activity of 1,320,000 mwu/gram. A fixed displacement pump was used to pump the slurry through a jet cooker (hydro-thermal series M104MSX manual stainless hydroheater, hydro-thermal corporation, Milwaukee, WI 53213) at a rate of 3.6 gal./min. at 194-197°F cooked paste temperature measured in line just after the cooked paste had passed through the jet cooker. The starch paste was cooked into a 75 gallon, V-bottom hold tank (approx. dimensions of 12"radius by 36"height with a 3"cone on the bottom) and held without agitation for 20 minutes, 16 minutes and 18 minutes at a temperature in the hold tank of about 178°F. Because the tank was not agitated, the paste collected evenly from top to bottom (plugged flow). After the designated amount of hold time, a second pump was started and the starch paste was pumped from the bottom of the hold tank through a second jet cooker set at 305 °F to deactivate the enzyme. Samples were collected and analyzed according to the procedures described in Example 1. 

Numerous modifications and variations of the above-described invention are expected to occur to those of skill in the art. Accordingly, only such limitations as appear in the appended claims should be appended thereon.

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