Physical modification of the viscosity characteristics of starchy flours
BACKGROUND OF THE INVENTION 
     A number of different physical treatments of starch have been proposed in the past, but, to our knowledge, physical modification by the methods used on starch have not been proposed for physical modification of starchy flours. One of the earliest physical treatments used on starch is dextrinization by heat, generally believed to have had its origins from observing the effect of the intense heat of a fire on starch stored in a warehouse (&#34;British Gums&#34;). &#34;Brewer&#39;s grits&#34; can be made from starch by a combination of heat and pressure applied to a thick starch slurry, usually by means of a drum dryer. The starch becomes gelatinized, and forms a film on the rotating dryer drum. The starch film is dried and then broken into small chunks to make a dustless grit product. Such &#34;grits&#34; are convenient to use in breweries as a carbohydrate source for fermentation. 
     One difficulty with heat treating a starchy flour in an aqueous slurry is that the starch component gelatinizes, and loses its discrete granular form. The gelatinized starch cannot be filtered, and excess water is difficult to remove without further changing the properties of the starchy flour. It is therefore desirable to preserve the granular structure of the starch component to the extent possible by using other liquids, such as lower alcohol, in which the starch component of the flour retains its granular structure, or at least some semblance of a granule form which is filterable, thereby making it possible to separate the physically modified starchy flour from the process liquid. 
     Various patents describe treating starch in alcohol, but none were found which describe such treatment of a starchy flour. Typical of such patents showing starch treatment is U.S. Pat. No. 2,587,650 issued Mar. 4, 1952 to Carl E. Rist et al. This patent describes the use of a lower alkanol (methanol, 85 volume percent), heat (105°-125° C.), and pressure (1 and 6 atmospheres or more) to physically treat starch. This reference points out that the process is &#34;readily adaptable to continuous operation and/or to recycling and reuse of the extracting solvent&#34; (Column 3, lines 45-46). There is no mention of similarly treating starchy flours, however. 
     A somewhat later series of patents includes U.S. Pat. No. 3,586,536 issued June 22, 1971. This patent describes heating starch slurried in methanol in a confined zone to a temperature in the range of 225° F. to about 300° F. for a time &#34;not in excess of thirty minutes.&#34; There is no description of such treatment of starchy flours, though. This patent states that &#34;ethanol, isopropanol and acetone are considered to be inoperable in our invention.&#34; See: U.S. Pat. No. 3,586,536, Column 7, lines 2-4. These latter organic liquids were said to result in either insufficient reduction of the fat content of the starch, or incipient gelatinization of the starch. 
     U.S. Pat. No. 3,617,383 issued Nov. 2, 1971 to Thurston et al., describes in great detail the effect on starch caused by the solvent treatment of starch in a confined zone. The process temperatures in the examples range from 230°-320° F. Starchy flours are not disclosed as a substance which may be subjected to the method described in this patent, however. 
     SUMMARY OF THE INVENTION 
     This invention is directed to an improved process for physically modifying a starchy flour. The starchy flour may be slurried in an aqueous, lower alkanol liquid under conditions of elevated temperature and pressure, and treated for a time sufficient to change its viscosity characteristics. More particularly, in the preferred method of the invention, a starchy flour is slurried in aqueous ethanol and forced through a continuous tubular reactor under pressures up to about 200 psig., and at temperatures up to about 340° F. The alcohol concentration is preferably about 80-95% ethanol, and 5-20% water, and indirect heating is provided to the continuous tubular reactor to maintain the temperature therein at about 140°-170° C. (284°-338° F.). The residence time of the starchy flour slurry in the continuous tubular reactor is about 1-30 minutes. 
     As the starchy flour is forced through the continuous tubular reactor under pressure and heat, its viscosity characteristics are changed. The treated starchy flour has definite stabilized viscosity characteristics, which makes it well-suited for use in baby foods, and in other uses in which a stable thickening effect is required. Although the exact nature of the change in the starchy flour which causes the change in its viscosity behavior is not known, it is considered possible that it may be due to crosslinking of protein molecules caused by the combined effects of the treatment. 
    
    
     EXAMPLE I 
     An oat flour was heat treated according to the method of the subject invention. The oat flour contained starch, and had the following analysis. 
     
         ______________________________________                                    
Moisture       9.3% by weight                                             
Ash            2.31% by weight                                            
Protein/Fiber 29.1% by weight                                             
Protein       17.96% by weight (as is basis)                              
Fat            7.05% by weight (as is basis)                              
Starch        55-70% by weight (dry solids basis)                         
Other Components                                                          
              Balance                                                     
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     It is expected that each of the above analysis may vary, in some instances by as much as plus or minus six percent, depending on the variety of oat flour. Prior to treatment, the above oat flour gave the following Brabender values: (a sample containing 6% oat flour in water pH 6.5 buffer and salt was used). 
     
         ______________________________________                                    
                               After 30                                   
                                      After 10                            
Pasting               Initial  minutes                                    
                                      minutes                             
Temperature                                                               
          Peak Viscosity                                                  
                      at 95° C.                                    
                               at 95° C.                           
                                      at 50° C.                    
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60.5° C.                                                           
          245         170      140    355                                 
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     A 2000 g. sample of the above oat flour was slurried in 4000 g. of denatured ethanol (35A) and was heated in a confined zone under pressure to 150° C. (302° F.) for five minutes and then cooled rapidly to room temperature (about 70°-80° F., or 21.1°-26.7° C.). The resulting treated oat flour was then filtered and dried. The product was then checked for Brabender viscosity with the following results: (a 6% by weight sample in pH 6.5 buffer with salt was used). 
     
         ______________________________________                                    
Initial Viscosity                                                         
            After 30 minutes                                              
                           After 10 minutes                               
at 95° C.                                                          
            at 95° C.                                              
                           at 50° C.                               
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120         185            340                                            
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     As compared to the oat flour before heat treatment, the above treated oat flour showed significant thin-thick viscosity behavior. The initial viscosity was the lowest and the viscosity continued to increase throughout the test. The Brabender test was repeated on the above treated oat flour with the following results: (6% by weight sample in pH 6.5 buffer with salt). 
     
         ______________________________________                                    
Initial Viscosity                                                         
            After 30 minutes                                              
                           After 10 minutes                               
at 95° C.                                                          
            at 95° C.                                              
                           at 50° C.                               
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200         210            360                                            
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     The above repeated viscosity test also indicated that the physically treated oat flour has definite thin-thick viscosity behavior when heated. 
     EXAMPLE II 
     The treated oat flour of Example I was then tested in blueberry baby food puree having the following formula: 
     
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Component A                                                               
Ingredient    percent by weight                                           
                              g.                                          
______________________________________                                    
water         17.0            255                                         
salt          0.12            1.8                                         
sugar         9.4             141                                         
blueberries   17.9            268.5                                       
pH is then adjusted to 3.25 with citric acid (about 3.8 g.)               
Component B                                                               
water         8.8             132                                         
oat flour     3.8             57                                          
Component C                                                               
blueberries   34.18           512.7                                       
sugar         8.8             132.0                                       
Procedure:                                                                
1.   Fruit and water part of Component A is first liquefied               
     by means of a blender, then salt and sugar are added.                
2.   Component B is then slurried (water and oat flour).                  
3.   Component is then liquefied in a blender (Osterizer).                
4.   Component A is placed in a steam jacketed kettle, and is             
     brought to a rolling boil.                                           
5.   Component B is then added and cooked for 90 seconds                  
     205° F. for two minutes).                                     
6.   The steam is shut-off, and Component C is stirred in with            
     a wire whip                                                          
7.   The resulting blend of A, B, &amp; C is then heated to 180° F.    
     and placed in cans which                                             
     are then sealed. Means is provided                                   
     to measure the internal temperature of the food mass in              
     the can                                                              
8.   Run Bostwick at about 160° F. before retorting.               
9.   Retort in continuous oil bath at 240° F. up to 265°    
     F.,                                                                  
     internal can temperature. -10. Take Bostwick and Brookfield          
     viscosity of retorted                                                
     material.                                                            
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     The above formula was identified as Sample A (3.8% by weight oat flour) in tests. A second formula was also made up, using all the same proportions as set forth above, except that 3.0% by weight treated oat flour was used. The latter formula was identified as Sample B in subsequent tests. Results of Bostwick viscosity tests for Samples A and B are set forth below: 
     
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Oat                         Time  Retorted                                
Flour                       To Reach                                      
                                  Brook-                                  
% by Bostwick    Retorted Bostwick                                        
                            Internal                                      
                                  field                                   
Weight                                                                    
     5&#34; 10&#34;                                                               
           15&#34;                                                            
              30&#34;                                                         
                 5&#34;                                                       
                   10&#34;                                                    
                      15&#34;                                                 
                         30&#34;                                              
                            Can Temp.                                     
                                  Visc.                                   
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A 3.8                                                                     
      9.2                                                                 
         7.8                                                              
           10.2                                                           
              10.7                                                        
                 4.5                                                      
                   5.0                                                    
                      5.5                                                 
                         6.0                                              
                            4 minutes                                     
                                  11,400                                  
B 3.0                                                                     
     11.0                                                                 
        11.7                                                              
           12.2                                                           
              12.7                                                        
                 5.6                                                      
                   6.4                                                    
                      6.7                                                 
                         7.3                                              
                            3 minutes                                     
                                   6,600                                  
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     The sample B containing 3.0% by weight treated oat flour was the best all-around product in the above tests. Because the above Sample B rated so well in the above tests, it was subjected to further tests in the same blueberry-containing baby food formula. At 4 pH buffer, the Brookfield viscosity readings were as set forth below: 
     
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                                 Time to F.sub.o                          
Hot    Before Retort                                                      
                    After Retort 12 minutes                               
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 75    1450          400         12.5                                     
At 6.5 pH buffer, the Brookfield viscosity                                
readings were as follows:                                                 
325    1500         2250         35.0                                     
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     The above baby food (Sample B) was also evaluated for texture, color, flavor, and viscosity, and was rated excellent. 
     Example III 
     Corn flour was also subjected to the same physical treatment in alcohol as described above. The corn flour used had the following general analysis: 
     
         ______________________________________                                    
Moisture      10.6% by weight                                             
Ash            1.07% by weight                                            
Protein/Fiber 14.8% by weight                                             
Protein        6.90% by weight (as is basis)                              
Fat            3.78% by weight (as is basis)                              
Starch        60-80% by weight (dry solids basis)                         
Other Components                                                          
              Balance                                                     
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     The above analysis may vary, in some instances by as much as plus or minus ten percent, depending on the variety of corn and milling process used. The Brabender test results for the subject corn flour were as follows: 
     
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                  Initial                                                 
Pasting  Peak     Viscosity                                               
                           After 30 min.                                  
                                   After 10 min.                          
Temp. (°C.)                                                        
         Viscosity                                                        
                  at 95° C.                                        
                           at 95° C.                               
                                   at 50° C.                       
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75.5     300      210      260     420                                    
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     The above corn flour was heated in denatured ethanol (35A) following the process generally described in Example I for oat flour to produce a heat-inhibited, cook-up starchy flour with the results set forth below. Two samples were prepared using the reaction conditions set forth: 
     
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Brabender Results (pH 6.5 buffer, 6% starch)                              
                  Brabender Results (B.U.)                                
Reaction Conditions     Ini-    30 min./                                  
                                      10 min./                            
time(min)                                                                 
        temp.(°C.)                                                 
                  Base Starch                                             
                            tial 95° C.                            
                                        50° C.                     
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20      162-163   Corn Flour                                              
                             45   80    120                               
15      143-144   Corn Flour                                              
                            165  160    210                               
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     EXAMPLE IV 
     Barley flour was subjected to physical treatment as set forth below. The barley flour used has the following analysis: 
     
         ______________________________________                                    
Moisture      10.80% by weight                                            
Ash            3.10% by weight                                            
Protein/Fiber 19.96% by weight                                            
Protein       12.21% by weight (as is basis)                              
Fat            2.42% by weight (as is basis)                              
Starch        55-70% by weight (dry solids basis)                         
Other Components                                                          
              Balance                                                     
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     The above analysis may vary, in some instances by as much as plus or minus ten percent, depending on the variety of barley and the milling process used. 
     
         ______________________________________                                    
Brabender Results (6% in pH 6.5 buffer with salt)                         
                    Initial           After                               
Pasting   Peak      Visc.    After 30 min.                                
                                      10 min.                             
Temperature                                                               
          Viscosity at 95° C.                                      
                             at 95° C.                             
                                      at 50° C.                    
______________________________________                                    
60.5° C.                                                           
          205       190      170      320                                 
(@141° F.)                                                         
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     The above barley flour (2200 g; or 1955.8 g. dry solids basis) was slurried in 4000 g, of denatured ethanol (35A), and was heated to 165° C. (329° F.) for about 1-60 minutes. The treated barley flour was then cooled to room temperature qabout 70°-80° F.). The flour was then filtered and washed with additional denatured alcohol (35A), and then dried. The treated barley flour had the following viscosity characteristics: 
     
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Brabender Results (6% in pH 6.5 buffer and salt)                          
Initial Viscosity                                                         
            Viscosity after 30                                            
                          Viscosity after 10                              
at 95° C.                                                          
            minutes at 95° C.                                      
                          minutes at 50° C.                        
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70          90            215                                             
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     EXAMPLE V 
     Barley flour was treated in two ways for comparison in this example. A first Sample A was treated as follows: A slurry of 2000 g. (1778 g. dry solids basis) of barley flour in 4000 g. of denatured alcohol (35A) was heated to 150° C. (302° F.) for five minutes, and then cooled to room temperature (70°-80° F.). The treated barley flour was filtered and dried. Some of the untreated barley flour (designated Sample B) was heated without adding any alcohol at the same temperature 150° C. (302° F.) for the same period of time (5 minutes). The viscosities of Sample A and Sample B treated barley flours were then measured with the following results: 
     
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Brabender Results (6% pH 6.5 buffer with 1% NaCl)                         
                  Initial  Viscosity                                      
                                    Viscosity                             
        Peak      Viscosity                                               
                           After 30 After 10                              
Sample  Viscosity at 95° C.                                        
                           Min. at 95° C.                          
                                    Min. at 50° C.                 
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A (alcohol                                                                
        120        80      120      265                                   
slurry,                                                                   
heat                                                                      
treated)                                                                  
B (dry  150       100      130      270                                   
heat                                                                      
treated)                                                                  
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     The above viscosity comparisons for Samples A and B show that a dry, physical heat treatment of short duration will also modify the viscosity behavior of a barley flour. The thin-thick viscosity changes upon heating are not as pronounced with Sample B and with Sample A but there is a definite and measurable shift of the dry, heat-treated barley flour from its pretreatment viscosity behavior to that of an initially thin, but subsequently thicker product. 
     EXAMPLE VI 
     The above treated oat and barley flours of Example I, IV and V(A) were still retorted in 4.0 and 6.5 pH buffer using 5% dry solids basis of each starchy flour sample in water. The samples were retorted at 260° F. to F o  (sterilization index) of 12. The respective starchy pastes were steam cooked for 10 minutes after reaching 185° F. and then retorted. The test results were as follows: 
     
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4.0 pH Buffer        6.5 pH Buffer                                        
Brookfield Visc. (cps)                                                    
                Time To                                                   
                     Brookfield Visc. (cps)                               
                                Time To                                   
        Before                                                            
            After                                                         
                F.sub.o 12                                                
                        Before                                            
                            After                                         
                                F.sub.o 12                                
Sample                                                                    
    Hot Retort                                                            
            Retort                                                        
                in min.                                                   
                     Hot                                                  
                        Retort                                            
                            Retort                                        
                                in min.                                   
__________________________________________________________________________
I   20  350 1780                                                          
                14.5 20  200                                              
                            3800                                          
                                15.0                                      
IV  87.5                                                                  
        780 1800                                                          
                22.5 67.5                                                 
                        1250                                              
                            5800                                          
                                21.5                                      
V(A)                                                                      
    100 500 1160                                                          
                18.5 85 1700                                              
                            5900                                          
                                23.0                                      
__________________________________________________________________________
 
    
     With the exception of Sample IV in 4.0 pH buffer, all of the samples exhibited thin-thick viscosity behavior during the test. Sample IV, which was the treated barley flour of Example IV, did show good thin-thick viscosity behavior in the pH 6.5 buffer test.