REMOISTENING OF THERMALLY INHIBITED STARCH AND/OR FLOUR

Abstract

Disclosed is a process for the treatment of a raw material containing thermally inhibited starch and/or thermally inhibited flour as its largest constituent, whereby the moisture content of the raw material is at most 8 wt. %, including a remoistening step wherein between 0.1 and 30 wt. % of an aqueous phase is added to the raw material to form a product containing remoistened starch and/or remoistened flour.

Claims

1: A process for the treatment of a raw material containing thermally inhibited starch and/or thermally inhibited flour as its largest constituent, whereby the moisture content of the raw material is at most 8 wt. %, comprising a remoistening step wherein between 0.1 and 30 wt. % of an aqueous phase is added to the raw material to form a product containing remoistened starch and/or remoistened flour.

2: The process according to claim 1, wherein the raw material contains at least 40 wt. % thermally inhibited starch and/or thermally inhibited flour.

3: The process according to claim 1, wherein the raw material contains at least 75 wt. % thermally inhibited starch or at least 75 wt. % thermally inhibited flour.

4: The process according to claim 1, wherein the raw material consists essentially of thermally inhibited starch, thermally inhibited flour, or mixtures thereof.

5: The process according to claim 1, wherein the moisture content of the raw material is at most 5 wt. %, and has not been above 5 wt. % since the thermally inhibited starch and/or thermally inhibited flour in the raw material were prepared.

6: The process according to claim 1, wherein the moisture content of the raw material is at most 2 wt. %, and has not been above 2 wt. % since the thermally inhibited starch and/or thermally inhibited flour in the raw material were prepared.

7: The process according to claim 1, wherein during the remoistening step the temperature of the raw material and of the product upon its formation is brought to, and made to remain within, a range from 0° C. to 65° C., via cooling means.

8: The process according to claim 1, wherein the temperature of the raw material is at most 40° C.

9: The process according to claim 1, wherein the pH of the aqueous phase is at most 8.5 or at most 8.0.

10: The process according to claim 1, wherein the pH of the product upon its formation in the remoistening step is brought to a value lying between 4.0 and 9.0 or to a value lying between 4.5 and 8.0, via control of the pH of the aqueous phase.

11: The process according to claim 1, whereby the remoistening step is done such that the moisture content of the product is brought to a value lying between 6 and 16 wt. % or to within 4 wt. % of its equilibrium value.

12: The process according to claim 1, wherein the remoistening step is done not later than three months after the thermal inhibition of the starch and/or flour has been done.

13: The process according to claim 1, wherein the thermally inhibited starch and/or thermally inhibited flour is selected from the group consisting of thermally inhibited rice starch and/or thermally inhibited rice flour, thermally inhibited wheat starch and/or thermally inhibited wheat flour, thermally inhibited maize starch and/or thermally inhibited maize flour, thermally inhibited potato starch and/or thermally inhibited potato flour, any waxy variants of the aforementioned starches and/or flours, and a mixture of the aforementioned starches and/or flours.

14: The process according to claim 1, wherein the raw material consists essentially of a starch selected from the group consisting of thermally inhibited rice starch, thermally inhibited waxy rice starch, thermally inhibited wheat starch, thermally inhibited waxy wheat starch, thermally inhibited maize starch, thermally inhibited waxy maize starch, thermally inhibited potato starch, thermally inhibited waxy potato starch, and a mixture thereof.

15: The process according to claim 1, whereby the process does not comprise a slurrying step, wherein a slurry of the raw material or of the product containing remoistened starch and/or remoistened flour would be formed.

Description

[0050] In the figures:

[0051] FIG. 1 shows a Brabender curve of the remoistened starch of Example 1.

[0052] The invention will be illustrated with the following examples, without being limited thereto.

EXAMPLES 1-3

[0053] A thermally inhibited waxy rice starch was, 13 days after its inhibition (during which time the thermally inhibited waxy rice starch was stored under ambient conditions in closed big bags having an inner liner), subjected to a remoistening step. The remoistening was executed in a Lödige ring layer mixer CM 20. 10 kg of raw material was used per example. The temperature, pH, and moisture content of the raw material are given in Table 1. Also given in Table 1 are temperature and pH of the aqueous phase, which consisted of liquid water, and certain properties of the product consisting of remoistened starch upon its formation (moisture content, temperature, viscosity, tan δ, and pH). In Example 3, the low pH of the aqueous phase was achieved via the addition of sulfuric acid, starting from the same water as used in Examples 1 and 2. Additionally, a Brabender curve of the remoistened starch of Example 1 is given in FIG. 1. The Brabender curve was determined at 6 wt. % dry matter in de-ionised water; the total sample weight was 500 g, the measuring speed was 75/min. FIG. 1 shows, as is customary, two curves: both the measured temperature profile—this is the curve starting at 50° C., going up to about 95° C., staying at about 95° C. during 15 minutes, followed by cooling to 20° C.—as well as the viscosity curve expressed in Brabender units (BU).

[0054] The gel was prepared at 94° C. in a Stephan UMSK 5 cooker, using 135 g (dry matter) starch, citric acid and trisodium citrate to acidify and buffer to pH 3.6, and sufficient water to obtain a total weight of 2,500 g, whereby the citric acid and trisodium citrate were combined with the water before the starch was added. After cooling to 25° C., an intensive shearing action on the gel was done by means of a Silverson L4RT mixer using a square hole (2.4 mm) high shear screen mixer head at 5,000 rpm during 1 minute. The selection of rpm is done based a.o. on the nature of the gel; thus, in further examples hereinbelow it may be that another rpm is chosen in order to obtain the most meaningful insight into material behaviour. The rpm as used will be reflected in the notation of viscosity parameter by means of a subscript, whereby indicates an rpm of 3,000, indicates an rpm of 5,000, etc.

[0055] The viscosity and tan δ of a gel, made from the starch concerned, that had first been subjected to an intensive shear action, were determined at a temperature of 20° C. by means of an Anton Paar Rheometer (parallel plate-plate configuration; the plate diameter was 40 mm). As meant herein, the term tan δ is used in its common meaning of being a loss tangent in the linear viscoelastic region. It gives a ratio between viscous and elastic properties of a system, showing which one is the dominant one. With a tan δ value of 1, the elastic and viscous properties of the material are equal. The smaller the loss tangent is, the more elastic is the material.

[0056] The viscosity at 0.88 s.sup.−1 was determined in a viscosity curve measurement wherein the shear rate varied from 0.1 to 100 s.sup.1.

[0057] The tan δ was determined from the results of an amplitude sweep measurement having the following characteristics: deformation from 0.01 to 1000%, frequency 1 Hz.

[0058] In the Examples and Comparative Experiments herein, the tan δ is always determined on a gel that has first been subjected to shear forces as described above, at the rpm as given per Example or Comparative Experiment.

TABLE-US-00001 TABLE 1 Aqueous Raw Material phase Temp. Moisture Temp. Cooling/heating during Remoistened Starch # (° C.) pH (wt. %) pH (° C.) remoistening tan δ pH 1 20 7.8 0.4 7.3 19 None - no use of double jacket 12.2 37  5130 0.51 7.6 2 20 7.8 0.4 7.3 19 Heating - water at 83° C. was 11.0 64* 4570 0.54 7.6 applied to the double-jacket 3 20 7.8 0.4 1.6 19 None - no use of double jacket 12.0 41  5440 0.49 6.5 Legend to Table 1:  = Moisture content upon completion of the remoistening step (wt. %)  = Temperature upon completion of remoistening step (° C.)  = Viscosity (in mPa.s) at a shear rate of 0.88 s.sup.−1 of a gel of the starch that was first subjected to shearing at 5000 rpm * = No gelatinisation was observed, a.o. due to the moisture content not being high enough for gelatinisation to occur The tan δ was determined via amplitude sweep at a gel of the starch that was first subjected to shearing at the same rpm as was the gel for the determination of V.

COMPARATIVE EXPERIMENT A

[0059] A sample of the same raw material as used in Examples 1-3 was used to form a slurry, using the same aqueous phase as used in Examples 1-2. The slurry contained 30 wt. % of the raw material. The slurry was subsequently dried to a moisture content of 12 wt. % to form a slurried-dried starch by means of centrifugation followed by oven-drying at 40° C. The properties of the slurried-dried starch were determined to be:

TABLE-US-00002 2590 mPa .Math. s tan δ 0.88

[0060] As is clear from the results of the Examples and the Comparative Experiment A, the slurried-dried starch has suffered a significant worsening in properties as compared to the remoistened starch of the invention as the slurried-dried starch had a much lower viscosity after shearing and had less elastic properties as seen in the higher tan δ (as is known, the smaller the loss tangent tan δ is, the more elastic is the material).

COMPARATIVE EXPERIMENT B

[0061] The properties of the thermally inhibited waxy rice starch as such, i.e. the raw material as used in Examples 1-3 without having been subjected to any subsequent process step such as remoistening or slurrying, were measured. The properties were determined to be:

TABLE-US-00003 5940 mPa .Math. s tan δ 0.46

[0062] The results of Comparative Experiment B show that the step of remoistening according to the invention does not lead to a significant loss of properties, as can be seen by comparing the results with those of Examples 1-3; this in contrast to a known treatment such as the slurrying step of Comparative Experiment A.

EXAMPLE 4

[0063] A raw material consisting of a thermally inhibited waxy rice starch, was subjected to a remoistening step. Compared to the thermally inhibited waxy rice starch of examples 1-3, the thermally inhibited waxy rice starch as used in this Example 4 is characterised by a higher degree of thermal inhibition. The raw material was, seven days after its inhibition (during which time the thermally inhibited waxy rice starch was stored under ambient conditions in closed PE containers), subjected to a remoistening step. The remoistening was executed by means of a lab scale hand sprayer. The pH of the aqueous phase was 7.7. The pH of the remoistened starch was 6.5. The determination of viscosity and tan δ of a gel, made from the remoistened starch, that had first been subjected to an intensive shear action was determined as described in Examples 1-3 with the exception of the rpm in the Silverson mixer. The mixer was set at 9,000 rpm, indicated below with subscript ‘9’ at viscosity parameter . The results were as follows:

TABLE-US-00004 17,500 mPa .Math. s tan δ 0.13

COMPARATIVE EXPERIMENT C

[0064] A sample of the same raw material as used in Example 4 was used to form a slurry using a the same aqueous phase as in Example 4. The slurry contained 30 wt. % of the raw material. The pH of the slurry was 7.3. The slurry was subsequently dried to a moisture content of 12 wt. % to form a slurried-dried starch by means of centrifugation followed by oven-drying at 40° C. The properties of the slurried-dried starch were then determined to be:

TABLE-US-00005 13,500 mPa .Math. s tan δ 0.15

COMPARATIVE EXPERIMENT D

[0065] The properties of the thermally inhibited waxy rice starch as such, i.e. the raw material as used in Example 4 without having been subjected to any subsequent process step such as remoistening or slurrying, were measured.

[0066] The properties were determined to be:

TABLE-US-00006 18,900 mPa .Math. s tan δ 0.12

EXAMPLE 5

[0067] A thermally inhibited waxy maize starch was, three months after its inhibition, used as raw material for a remoistening step. The pH of the aqueous phase was 7.7. The remoistening step and subsequent measurements were executed as described in Examples 1-3, with the exception of the rpm in the Silverson mixer. The mixer was set at 9,000 rpm. The pH of the remoistened starch was 7.2. The results were as follows:

TABLE-US-00007 12,200 mPa .Math. s tan δ 0.23

COMPARATIVE EXPERIMENT E

[0068] The properties of the thermally inhibited waxy maize starch that was used as raw material in Example 5 as such, i.e. without having been subjected to remoistening or slurrying, were measured. The properties were determined to be:

TABLE-US-00008 13,800 mPa .Math. s tan δ 0.21

COMPARATIVE EXPERIMENT F

[0069] A sample of the same raw material as used in Example 5 was used to form a slurry, using the same aqueous phase as used in Example 5. The slurry was subsequently dried to a moisture content of 12 wt. % by means of filtration under vacuum and further drying in a rapid dryer (TG 200, Retsch) to form a slurried-dried starch. The properties of the slurried-dried starch were determined to be:

TABLE-US-00009 8,570 mPa .Math. s tan δ 0.31

EXAMPLES 6, 7

[0070] A thermally inhibited waxy wheat starch was, 14 days after its inhibition, used as raw material for a remoistening step. The remoistening step and subsequent measurements were executed as described in Examples 1-3, with the exception of the rpm in the Silverson mixer—the mixer was set at 7,000 rpm—and the execution of the remoistening which was done by means of a lab scale hand sprayer. The results were as follows:

TABLE-US-00010 Example 6 7 pH of aqueous phase 7.7 5.8 pH of remoistened starch 7.2 6.7  (mPa .Math. s) 7,450 9,870 tan δ 0.42 0.34

COMPARATIVE EXPERIMENT G

[0071] The properties of the thermally inhibited waxy wheat starch that was used as raw material in Examples 6 and 7 as such, i.e. without having been subjected to remoistening or slurrying, were measured. The properties were determined to be:

TABLE-US-00011 10,000 mPa .Math. s tan δ 0.34

COMPARATIVE EXPERIMENT H

[0072] A sample of the same raw material as used in Examples 6 and 7 was used to form a slurry, using the same aqueous phase as used in Example 6. The slurry was subsequently dried to a moisture content of 12 wt. % by means of filtration under vacuum and further drying in a rapid dryer (TG 200, Retsch) to form a slurried-dried starch. The properties of the slurried-dried starch were determined to be:

TABLE-US-00012 5,440 mPa .Math. s tan δ 0.51

EXAMPLE 8

[0073] A thermally inhibited waxy rice flour was, 21 days after its inhibition, used as raw material for a remoistening step. The remoistening step and subsequent measurements were executed as described in Examples 1-3, with the exception of the following points: [0074] The gel preparation in the Stephan cooker was done with 225 g (dry matter) of flour, still on a total weight of 2,500 g; [0075] The rpm in the Silverson mixer. The mixer was set at 3,000 rpm; and [0076] The remoistening was done by means of a lab scale hand sprayer.
The results were as follows:

TABLE-US-00013 22,500 mPa .Math. s tan δ 0.57

COMPARATIVE EXPERIMENT I

[0077] The properties of the thermally inhibited waxy rice flour that was used as raw material in Example 8 as such, i.e. without having been subjected to remoistening or slurrying, were measured. The properties were determined to be:

TABLE-US-00014 20,900 mPa .Math. s tan δ 0.58

COMPARATIVE EXPERIMENT J

[0078] A sample of the same raw material as used in Example 8 was used to form a slurry, using the same aqueous phase as used in Example 8. The slurry was subsequently dried to a moisture content of 12 wt. % by means of filtration under vacuum and further drying in a rapid dryer (TG 200, Retsch) to form a slurried-dried starch. The properties of the slurried-dried starch were determined to be:

TABLE-US-00015 18,700 mPa .Math. s tan δ 0.65

[0079] The above Examples and Comparative Experiments show that the properties of a raw material containing thermally inhibited starch of flour are preserved better in the process of the invention as compared to the known process of slurrying followed by drying.

EXAMPLES 9-11

[0080] A thermally inhibited waxy rice starch was, 14 days after its inhibition, used as raw material for a remoistening step. The remoistening step and subsequent measurements were executed as described in Examples 1-3. The results were as follows:

TABLE-US-00016 Example 9 10 11 pH of aqueous phase 8.0 2.5 1.5 pH of remoistened starch 7.6 7.3 6.5  (mPa .Math. s) 7,260 9,530 9,770 tan δ 0.36 0.36 0.35

COMPARATIVE EXPERIMENT K

[0081] The properties of the thermally inhibited waxy rice flour that was used as raw material in Examples 9-11 as such, i.e. without having been subjected to remoistening, were measured. The properties were determined to be:

TABLE-US-00017 11,800 mPa .Math. s tan δ 0.30