METHOD OF MAKING FUNCTIONAL FIBER HAVING IMPROVED DEWATERING EFFICIENCY

Abstract

The technology disclosed in this specification pertains to methods for increasing the dewatering efficiency of a sheared plant fiber, for example citrus fiber, by shearing the plant material in a slurry of water and organic solvent. The plant fibers obtained from the method provide significant viscosity even when using little alcohol. The obtained citrus fibers may be used in edible, cosmetic, household, or an industrial compositions.

Claims

1. A method for increasing the dewatering efficiency of a sheared plant fiber comprising: (i) forming a slurry having a solid phase and a liquid phase comprising a comminuted depectinated plant material an organic solvent and an aqueous phase; (ii) applying shear to the slurry; and (iii) recovering the plant fiber from the slurry.

2. The method of claim 1 wherein the solvent is an alcohol.

3. The method of claim 1 wherein the depectinated plant fiber has a pectin content of less than about 19% by weight (d.b.).

4. The method of claim 1 wherein the slurry’s liquid phase comprises water and organic solvent, optionally wherein the slurry comprises from from about 5% to about 25%.

5. The method of claim 1 wherein the shear energy is applied via a pressure drop across a restricted orifice or nozzle and the pressure drop is at least about 100 to about 5000 bar.

6. The method of claim 1 wherein the shear energy is applied to the slurry by a rotor/stator homogenizer rotating at from about 1,000 to about 20,000 rpm.

7. The method of claim 1 wherein the slurry is sheared in one pass, at least one pass, or at least 2 passes.

8. The method of claim 1 wherein the slurry’s solid phase comprises about 0.25 to about 15% (d.b.).

9. The method of claim 1 wherein recovering the plant fiber removes at least about 10% of the liquid from the dispersed fiber.

10. The method of claim 1 further comprising drying the recovered plant fiber, wherein, optionally, the dried plant fiber has moisture content of less than about 10%.

11. The method of claim 1 further comprising washing the depectinated plant material prior to applying the shear plant material, optionally wherein the washing step whitens the plant material.

12. The method of claim 1 further comprising washing the depectinated plant material in a solution comprising from about 5% to about 30% v/v of an organic acid, wherein the washing is performed prior to applying the shear.

13. A sheared plant fiber or citrus fiber made by a process as described in claim 1 capable of forming an aqueous dispersion at 1% fiber (d.b.) that has one or more characteristics selected from the group consisting of: (a) median particle size of less than about 45 microns; (b) a 90th percentile particle size of from less than about 100 microns; (c) a viscosity at 10 s.sup.-1 of greater than about 3 Pa.s (e) an elastic modulus (G′) at 1 rad/s of greater than about 200 Pa and (f) a water holding capacity of from about 60 to about 100 g/g.

14. A sheared plant fiber or citrus fiber capable of forming an aqueous dispersion at 1% fiber (d.b.) having a median particle size of less than about 45 microns.

15. The sheared plant fiber or citrus fiber of claim 14 capable of forming an aqueous dispersion at 1% fiber content (d.b.) having a 90th percentile particle size of from less than about 100 microns.

16. The sheared plant fiber or citrus fiber of claim 14 capable of forming an aqueous dispersion at 1% fiber (d.b.) having a viscosity at 10 s.sup.-1 of greater than about 3 Pa.s.

17. The sheared plant fiber or citrus fiber of claim 14 capable of forming an aqueous dispersion at 1% fiber (d.b.) having a Bostwick distance of less than about 6.0 cm.

18. The sheared plant fiber or citrus fiber of claim 14 capable of forming an aqueous dispersion at 1% fiber (d.b.) having an elastic modulus (G′) at 1 rad/s of greater than about 200 Pa.

19. The sheared plant fiber or citrus fiber of claim 14 capable of forming an aqueous dispersion at 1% fiber (d.b.) having a water holding capacity of from about 60 to about 100 g/g.

Description

EXAMPLE 1 - EFFECT OF SHEAR ON RECOVER OF CITRUS FIBER FROM WATER

[0071] Example 1 evaluates the effect of shear on the ability to recover citrus fiber by preparing Sample 1, which is depectinated lime peel that was sheared in water.

[0072] 110 g of dried lime peel were dispersed in 2 L of deionized water. The dispersion was heated to 70° C. and pH adjusted to 1.8 to partially hydrolyze and solubilize pectin. After 4 hours, the dispersion was filtered using a wine press and muslin bag to separate pectin juice from insoluble peel components to produce a spent peel material. The spent peel filter material was tested by thermal balance and found to contain 89% moisture and 11% solids.

[0073] After diluting 510 g of spent peel material to 1250 g with water and treating with 20 mL 15% peracetic acid at 70° C. for 1 hour, the whitened slurry was processed using a Silverson LM5-A shear mixer at 10,000 rpm for 5 minutes using the 2 mm circular shearing screen. The sheared aqueous mixture was transferred to a muslin bag to dewater. While pressing with a wine press, the finer homogenized fibers passed through the pores of the muslin bag. The slurry was transferred to a 50-micron polyester filter cloth and again pressed within the wine press. No fluid could be extracted despite applying the maximum hand pressure.

[0074] The result of this example illustrates the difficulty in recovering sheared citrus fiber from water.

EXAMPLE 2 - EFFECT OF SHEAR ON ISOPROPYL ALCOHOL RECOVERED CITRUS FIBERS

[0075] Example 2 evaluates the effect of shear on citrus fiber dispersed in alcohol solution by comparing an experimental sample (sample 2) that is sheared in isopropyl alcohol against an internally made control sample (sample 3) that is unsheared but was washed in isopropyl alcohol and against an unsheared commercial control (sample 4).

Sample Preparation

Sample 2 - Depectinated Lime Peel Sheared in Isopropyl Alcohol

[0076] 110 g of dried lime peel were dispersed in 2 L of deionized water. The dispersion was heated to 70° C. and pH adjusted to 1.8 to partially hydrolyze and solubilize pectin. After 4 hours, the dispersion was filtered using a wine press and muslin bag to separate pectin juice from insoluble peel components to produce a spent peel material. The spent peel filter material was tested by thermal balance and found to contain 89% moisture and 11% solids.

[0077] 510 g of this spent peel material was transferred to an IKA LR1000 reactor and brought to 1250 g with deionized water. The mixture was heated to 70° C. while gently stirring at 30 rpm. 20 mL of 15% peracetic acid was added to whiten the spent peel slurry. After 1 hr the whitened peel slurry was dewatered using a wine press and muslin cloth to create a filter material. The spent peel filter material was tested by thermal balance and found to contain 90% moisture and 10% solids. 510 g of filter material was returned to the reactor and dispersed with a volume of 510 mL of 98% isopropyl alcohol. The alcoholic dispersion was processed with a Silverson LM5-A high shear mixer at 10,000 rpm to break up citrus fiber peel sections. The sheared slurry was then passed through a colander with 2 mm hole size to remove hard pieces of seeds which potentially may clog homogenizing equipment. The screened slurry was then introduced to an APV1000 high pressure homogenizer and passed one time across the homogenizing nozzle at a pressure of 14,000 psi. An aliquot of this homogenized slurry was filtered using a wine press and 50-micron polyester filter cloth to produce 200 g of fiber material retentate and 410 g of alcohol/water filtrate. Alcohol consumption to this first filtering stage was 1 mL isopropyl alcohol per 1 g of spent peel material. The filter material was dispersed a 2.sup.nd time in an additional 200 g of isopropyl alcohol. The slurry was stirred at room temperature for 30 minutes and then filter a second time to produce a twice alcohol washed fiber material. The material was broken up and dried within the LR1000 with the bottom plate set to 50° C., constant stirring at 30 rpm and with dry compressed air blowing through the reactor for 1 hour.

Sample 3 - Alcohol Washed, Unsheared Depectinated Lime Peel

[0078] Spent lime peel material was prepared as in Example1 and 2. After similarly diluting 510 g of spent peel material to 1250 g with water and treating with 20 mL 15% peracetic acid at 70° C. for 1 hour, the whitened peel slurry was dewatered using a wine press and muslin cloth to create a filter material. The spent peel filter material was tested by thermal balance and found to contain 91% moisture and 9% solids. 515 g of filter material was returned to the reactor and dispersed with a volume of 515 mL of 98% isopropyl alcohol. This alcoholic slurry was filtered using a wine press and 50-micron polyester filter cloth to produce a non-homogenized filter material. The filter material was dispersed a 2.sup.nd time in an equal proportion isopropyl alcohol to example 1. The slurry was stirred at room temperature for 30 minutes and then filter a second time to produce a twice alcohol washed non-homogenized fiber material. The material was broken up and dried within the LR1000 with the bottom plate set to 50° C., constant stirring at 30 rpm and with dry compressed air blowing through the reactor for 1 hour.

Sample 4 - Commercial Control

[0079] Sample 4 is an unsheared commercially available control citrus fiber.

Results - Functional Properties of Samples 2, 3, and 4

[0080] The fibers of Samples 2, 3, and 4 were added at 1% dry basis in deionized water with 300 ppm potassium sorbate as a preservative. The preparations were dispersed using a Silverson LM5-A laboratory mixer at 10,000 rpm for 10 minutes. To determine Bostwick viscosity, a Bostwick consistometer was leveled and the trough filled with the wet fiber dispersions. The trough gate was opened and the distance the fiber dispersion traveled over 30 seconds was recorded, with smaller distances indicating greater viscosity. The rheological properties of the fiber dispersions were also assessed with a TA Instruments AR-G2 rheometer using a vane geometry. A dynamic amplitude sweep was performed to identify the linear viscoelastic range. A dynamic frequency sweep was then performed at an amplitude selected from the linear viscoelastic range, and the G′ value at 1 rad/s was obtained. The viscosity value at a shear rate of 10 s-1 was extracted. The wet particle size distribution of the fibers dispersions was determined using a Malvern laser diffractometer, and values for the median and 90% percentile particle size were obtained. Results of these measurements are reported in Table 1.

TABLE-US-00001 Functional Characteristics of Sheared and Unsheared Fibers Sample Bostwick Distance (cm) G′ at 1 rad/s (Pa) Viscosity at 10 s-1 (Pa.s) Median Particle Size (microns) 90% Percentile Particle Size (microns) Sample 2 (alcohol sheared citrus fiber) 5.2 287.0 3.15 41.9 96.9 Sample 3 (unhomogenized alcohol recovered citrus fiber) 6.2 141.1 2.78 53.2 138.2 Example 4 (commercial control) 7.4 115.4 2.16 70.2 146.4

[0081] As seen the material sheared in water and isopropanol produced thicker mixtures when re-slurried and have smaller particle size than unsheared samples. The results of this example demonstrate that citrus fiber sheared in water/isopropanol mixture can be readily functionalized compared to unsheared plant material, and while being highly recoverable from the shearing process slurry.

EXAMPLE 3 - DEWATERING EFFICIENCY OF FIBER HOMOGENIZED IN ISOPROPYL ALCOHOL

[0082] This example illustrates how dewatering efficiency change with concentration of isopropyl alcohol.

[0083] Sample 5 is a control sample prepared like Sample 1 and further illustrates the difficulty of dewatering a citrus peel sheared in water.

[0084] Samples 6, 7 and 8 were prepared like Sample 2, but with various concentrations of isopropyl alcohol but filtered only once through the 50-micron polyester filter cloth. Sample 6 is a 50% (v/v) mixture of alcohol and water, Sample 7 is a 75% water mixture (v/v), and Sample 8 uses an 87.%% water mixture (v/v). Dewatering efficiency is reported in Table 2 and is the percent juice recovered (g) from pressed sheared material versus total weight of sheared material and juice (i.e. dewatering efficienty (%) = (juice (g)/ juice (g) +material (g))*100).

TABLE-US-00002 Dewatering Efficiency fiber amount (g) total volume (ml) water fraction (% v/v) Juice (g) Material (g) Dewatering efficiency (%) 35.23 1175 100 30.64 650 4.5 35.23 1175 50 322 499 39.2 35.23 1175 75 204.4 679 23.1 35.23 1175 87.5 205 660 23.7

[0085] As seen, while dewatering efficiency increase with increased isopropyl alcohol concentration significant improvements in dewatering efficiency are observed using limited isopropyl alcohol.