Thermally inhibited starch and starchy flours

Abstract

The present invention relates to thermally inhibited starch and starchy flours produced by heat treatment of native starch that is pre-dried where necessary to a dry matter content of more than or equal to 95% by weight, preferably 98% by weight, particularly preferably 99% by weight, wherein said starch, pre-dried where necessary, is treated in the presence of at least 0.1% by volume of oxygen at a product temperature in excess of 100° C. in a vibrating spiral conveyor.

Claims

1. A method of producing a thermally inhibited starch or starchy flour comprising heat-treating for 24 minutes to 72 minutes, at a pH of 7 to 12, a native starch in a spiral vibratory conveyor in the presence of at least 0.1% by volume oxygen to atmospheric oxygen concentrations at a product temperature of between 150 and 200° C., wherein the native starch has a dry matter content of 98% to 99% by weight and has been pre-dried, if necessary, to obtain the dry matter content.

2. The method of claim 1, wherein the native starch has a dry matter content equal to 99% by weight and has been pre-dried, if necessary, to obtain the dry matter content.

3. The method of claim 1, wherein heat treatment is carried out in the presence of at least 0.5% by volume oxygen to atmospheric oxygen concentrations.

4. The method of claim 1, wherein heat treatment is carried out in the presence of atmospheric oxygen.

5. The method of claim 1, wherein heat-treating is carried out at a product temperature of between 155 and 175° C.

6. The method of claim 1, wherein the thermally inhibited starch or starchy flour is further defined as having an amylose content of less than 5% by weight.

7. The method of claim 6, wherein the thermally inhibited starch or starchy flour is further defined as having an amylose content of less than 2% by weight.

8. The method of claim 6, wherein the thermally inhibited starch or starchy flour is further defined as a starch originating from waxy corn.

9. A thermally inhibited starch or starchy flour produced by the method of claim 1, wherein the starch or starchy flour has a granular form.

10. The thermally inhibited starch or starchy flour of claim 9, further defined as having an amylose content of less than 5% by weight.

11. The thermally inhibited starch or starchy flour of claim 10, further defined as having an amylose content of less than 2% by weight.

12. The thermally inhibited starch or starchy flour of claim 10, further defined as a starch originating from waxy corn.

Description

DETAILED DESCRIPTION

(1) The present invention is now explained in more detail by reference to the following examples, which, however, are non-limiting.

(2) Viscosity Characterization:

(3) To characterize thermally inhibited starches and flours, the viscosity of starch and starchy flours is measured as a function of time and temperature and is compared with the starting, or reference, material. The viscosity is measured in a Brabender Viscograph-E (manufactured by Brabender Technologie KG) and is expressed in Brabender units. It is the resistance of the solution, measured as torque. The starch/water suspension is heated and cooled, at a constant rate of temperature increase and decrease, respectively, in a Brabender bowl rotating at a constant rotational speed. The temperature and the viscosity, in Brabender units, are recorded simultaneously. A graph is obtained by plotting temperature and Brabender units against time. Thermally non-inhibited starches usually gelatinize in a range between 60-70° C., reaching their maximum in the range from 65-95° C. If the temperature is held there for a certain period of time, the viscosity decreases (by what is known as the breakdown) from its peak value and then, on cooling, increases again to its end value.

(4) As is known from the prior art, inhibited starches differ from their starting material in showing a reduced breakdown. That means that, as the level of inhibition increases, the breakdown in viscosity becomes less and less until finally a plateau is formed. At the same time, there is also a reduction in the viscosity maximum.

(5) Brabender Method:

(6) For a neutral Brabender, all samples are suspended in a sufficient amount of demineralized water to give a 6.25% anhydrous solids starch slurry. The suspension is introduced into the sample dish of a Brabender Viscograph-E fitted with a 700 cmg measuring bowl. For the measurement, the sample is heated from 30° C. to 90° C. and held at this temperature for 30 minutes. Thereafter, it is cooled down again to 30° C. The peak maximum, the viscosity breakdown and the end viscosity are expressed in Brabender units.

(7) The following material and equipment is used in the examples: Native waxy corn starch (Agrana, AT) Chemically modified starch; Ajenajel 20.321 (Agrana, AT) Sodium bicarbonate, 106323 (Merck, AT) Demineralized water Thermally inhibited starch; Novation® 2300 (National Starch, US) Thermally inhibited starch; Novation® 2600 (National Starch, US) Spiral vibratory conveyor or spiral dryer (Revtech, FR) Kern analytical balance PLJ 4000-2M Sartorius moisture analyser MA40 WTW pH meter pH330 Brabender Viscograph-E with control unit and cooling (Brabender Technologie, DE) Haldenwanger Buchner funnel 127C-4 Whatmann® filter paper 589/1 Knf Laboport vacuum pump N820.3AT.18 Retsch dryer TG100 IKA stirrer RW 47D Retsch mill ZM 200, 1 mm insert Diverse laboratory accessories

(8) The spiral vibratory conveyor used is of pilot-plant scale and is dimensioned as follows:

(9) Ø (tube interior) 0.10 m, L (tube) 35 m and V (tube) 0.275 m.sup.3. The process parameters are set as follows: vibrational speed 100%, motor angle 45° and drive motor 100%.

(10) To ensure that drying is as fast and complete as possible, the two tube openings are opened with each spiral revolution. This enables the water to vaporize and prevents it from condensing on the tube wall. Plus, a constant O.sub.2 level is also guaranteed.

EXAMPLE 1

Alkalization of Starch

(11) 45% (w/w) native waxy corn starch was slurried with 55% (w/w) demineralized water and adjusted to a pH value of 9.5 with a 20% (w/w) solution of sodium bicarbonate. The slurry was vacuum-filtered on the Buchner funnel fitted with filter paper (Whatmann® 589/1) and the starch then dried at 60° C. to its equilibrium moisture content with the Retsch dryer.

(12) TABLE-US-00001 TABLE 1 Comparison of Brabender data obtained for the raw material (native WCS) and for the feedstock from Example 1 (1, hereinafter referred to as non-modified starch), where GT stands for the gelatinization temperature, PM the peak maximum, BD the breakdown and EV the end viscosity GT PM BD EV Name [° C.] [BE] [BE] [BE] 1 67.3 1066 777 546 Native WCS 68.0 1059 760 547

EXAMPLE 2

Drying: (130° C.)

(13) The starch from Example 1 was conveyed through the spiral at a product flow rate of 50 kg/h and a product temperature of 130° C. Metering was performed gravimetrically via the automatic metering station. After a cycle, a sample was withdrawn and analysed. As is evident from Table 2, the sample does not undergo a viscosity shift in the direction of a thermally inhibited starch but retains the viscosity profile of the non-modified starch.

(14) TABLE-US-00002 TABLE 2 Comparison of Brabender data obtained for the feedstock from Example 1 (non-modified starch), for a chemically modified starch (Agenajel 20.321) and for two commercially available inhibited starches (Novation ®) with the data obtained after drying (1), where GT stands for the gelatinization temperature, PM the peak maximum, BD the breakdown and EV the end viscosity Temp. GT PM BD EV Name [° C.] [° C.] [BE] [BE] [BE] 1 130 67.4 1408 1131 528 Non-modified control — 67.3 1066 777 546 Chem. mod. control — 65.6 668 32 1020 Novation ® 2300 65.2 506 1 771 Novation ® 2600 66.4 682 41 1011

EXAMPLE 3

190° C.

(15) The two tube ends were connected with a hose so as to enable recirculation of the product. All the openings at each turn of the spiral were open. The starch from Example 1 was added at a flow rate of 100 kg/h. After drying at 130° C. for 6 minutes, the heating temperature was raised in order to reach a product temperature of 190° C. and the product recirculated until it was seen to turn intensely brown and take on a different aroma. After each cycle (approx. 6 min), the hose was removed briefly by hand and a sample withdrawn.

(16) As is evident from Table 3, increasing the duration of treatment at a temperature of 190° C. results in starch which has a viscosity profile tending toward that of a chemically modified control sample and which is also comparable with the commercially available thermally inhibited products. The longer the starch is treated, the higher is the degree of inhibition, resulting accordingly in a lower viscosity.

(17) TABLE-US-00003 TABLE 3 Comparison of Brabender data obtained for the non-modified control, for a chemically modified starch and for two commercially available inhibited starches (Novation ®) with the data obtained after treatment at 190° C. for different lengths of time (1-5), where GT stands for the gelatinization temperature, PM the peak maximum, BD the breakdown and EV the end viscosity Temp. Time GT PM BD EV Name [° C.] [min] [° C.] [BE] [BE] [BE] 1 190 12 66.8 1117 741 631 2 190 18 66.5 1039 480 834 3 190 24 65.3 669 19 1016 4 190 30 63.3 419 0 634 5 190 36 62.0 207 0 371 Non-modified control — — 67.3 1066 777 546 Modified control — — 65.6 668 32 1020 Novation ® 2300 — — 65.2 506 1 771 Novation ® 2600 — — 66.4 682 41 1011

EXAMPLE 4

170° C.

(18) The samples were treated in the same way as in Example 2 except that heat treatment was carried out at a product temperature of 170° C. It is evident from Table 4 that thermal inhibition intensity increases with increasing treatment duration, and that thermostable samples are obtained which have a strongly reduced breakdown and have the properties of chemically modified starches.

(19) TABLE-US-00004 TABLE 4 Comparison of Brabender data obtained for the non-modified starch, for a chemically modified starch and for two commercially available inhibited starches (Novation ®) with the data obtained after treatment at 170° C. for different lengths of time (1-6), where GT stands for the gelatinization temperature, PM the peak maximum, BD the breakdown and EV the end viscosity Temp. Time GT PM BD EV Name [° C.] [min] [° C.] [BE] [BE] [BE] 1 170 18 67.0 1125 717 667 2 170 30 66.4 933 193 1224 3 170 36 66.2 842 101 1166 4 170 42 66.0 722 14 1103 5 170 48 65.9 653 3 1035 6 170 54 65.6 564 0 853 Non-modified control — — 67.3 1066 777 546 Modified control — — 65.6 668 32 1020 Novation ® 2300 — — 65.2 506 1 771 Novation ® 2600 — — 66.4 682 41 1011

EXAMPLE 5

150° C.

(20) The samples were treated in the same way as in Example 2 except that heat treatment was carried out at a product temperature of 150° C. In this case, there was only a low level of thermal inhibition and the starch obtained was only slightly more stable than a non-modified starch.

(21) TABLE-US-00005 TABLE 5 Comparison of Brabender data obtained for the non-modified control, for a chemically modified starch and for two commercially available inhibited starches (Novation ®) with the data obtained after treatment at 150° C. for different lengths of time (1-8), where GT stands for the gelatinization temperature, PM the peak maximum, BD the breakdown and EV the end viscosity. Temp. Time GT PM BD EV Name [° C.] [min] [° C.] [BE] [BE] [BE] 1 150 30 66.9 1146 653 743 2 150 36 66.8 1063 439 868 3 150 42 66.8 1208 561 923 4 150 48 66.7 968 227 1118 5 150 54 66.7 968 211 1204 6 150 60 66.9 936 205 1318 7 150 66 67.0 923 203 1320 8 150 72 66.6 915 166 1222 Non-modified control — — 67.3 1066 777 546 Modified control — — 65.6 668 32 1020 Novation ® 2300 — — 65.2 506 1 771 Novation ® 2600 — — 66.4 682 41 1011

(22) It is evident that the treatment of starch in in a spiral vibratory converter is a continuous process and that, the higher the temperature is set, the reaction will proceed exponentially faster. With the spiral vibratory converter, curves can be generated that are equivalent to those of commercially available thermally inhibited starches. It is clearly apparent that, at a higher temperature, the same result can be obtained in a shorter time than is obtained, at a lower temperature, in a longer time.

EXAMPLE 6

Application-Related Comparison of Thermally Inhibited Starches

(23) Three of the samples produced in the spiral vibratory converter (190° C./24 min, 170° C./36 min and 170° C./54 min) were processed in a 40° Brix cherry fruit preparation and tested for their suitability in a sensitive food system with an acidic pH.

(24) Table 6 below shows the formulation for the 40° Brix cherry fruit preparation used for application-related testing of the starch profiles produced.

(25) TABLE-US-00006 TABLE 6 Formulation for 40° Brix cherry fruit preparation Material Mass Water 153.00 Sour cherries cut in half 400.00 Sodium citrate 1.00 Sugar heat to 40° C. 300.00 Water 100.00 Starch addition of slurried starch, heat to 95° C. 45.00 Citric acid heat to 92° C., hold for 10 min 1.00 Total 1000.00

(26) In the following evaluation, the three samples are compared in terms of taste, appearance and viscosity/rheology.

(27) TABLE-US-00007 TABLE 7 List of results for differently produced thermally inhibited starches in a 40° Brix cherry fruit preparation Viscosity Viscosity Synaeresis [mm/30 s] [mm/30 s] in fruit prep. Texture of Blending in Starch pH D = 1 D = 14 D = 14 fruit prep. the yogurt Taste 190° 3.28 58 50 No Very good Good, very Typical 24 min satisfactory structure 170° C. 3.30 48 39 No Good, Good, very Typical 36 min somewhat satisfactory jellified structure 170° C. 3.32 60 66 No Good Good, very Typical 54 min satisfactory structure

(28) The Brabender viscosities of the samples according to the invention, produced in the spiral vibratory conveyor, are comparable with the quality of the Novation starches known from the prior art. In addition, they are able to substitute for chemically modified starches.

(29) The sample treated for 54 minutes at 170° C. has a viscosity curve similar to that of Novation 2300 and has a slightly higher viscosity.

(30) Both the sample treated for 42 minutes at 170° C. and the sample treated for 24 minutes at 190° C. show a viscosity profile that corresponds to that of Novation 2600 and thus to a commercially available thermally inhibited starch.