PURIFIED COAGULATED POTATO PROTEIN PRODUCT, METHODS FOR PROVIDING THE SAME, AND USES THEREOF

Abstract

The invention relates to the field of food ingredients. In particular, it relates to methods for providing highly purified coagulated potato protein having a desirable taste which is advantageously used for the fortification of food products. Provided is a method for providing a purified coagulated potato protein product, comprising (i) subjecting heat coagulated potato protein to one or more extraction step(s) with an alcoholic extraction solvent comprising (a) ethanol and water at a ratio in the range of 90:10 to 60:40 (v/v), or (b) propanol and water at a ratio in the range of 90:10 to 40:60 (v/v) at a pH in the range of 3 to 6, under conditions allowing for extraction of glycoalkaloids and lipids from said heat coagulated potato protein composition, followed by (ii) washing the extracted heat coagulated potato protein with water to obtain a purified coagulated potato protein product, followed by (iii) drying the purified coagulated potato protein product.

Claims

1. A method for providing a purified coagulated potato protein product containing less than 150 ppm triglycoalkaloid (TGA) and less than 1.5% based on dry solids (DS) lipids, comprising: (i) subjecting heat coagulated potato protein to one or more extraction step(s) comprising mixing heat coagulated potato protein at a concentration of about 30-200 g/L with an alcoholic extraction solvent comprising: (a) ethanol and water at a ratio in the range of 90:10 to 60:40 (v/v), or (b) propanol and water at a ratio in the range of 90:10 to 40:60 (v/v), at a pH in the range of 3 to 6, under conditions allowing for extraction of glycoalkaloids and lipids from said heat coagulated potato protein composition; (ii) washing the extracted heat coagulated potato protein with water to obtain a purified coagulated potato protein product; and (iii) drying the purified coagulated potato protein product.

2. The method according to claim 1, wherein the extraction solvent comprises (a) ethanol and water, or (b) propanol and water, at a ratio in the range of 85:15 to 60:40 (v/v).

3. The method according to claim 2, wherein the extraction solvent comprises ethanol and water at a ratio in the range of 90:10 to 60:40 (v/v).

4. The method according to claim 1, wherein the extraction solvent comprises isopropanol (IPA) and water at a ratio in the range of 90:10 to 40:60 (v/v).

5. The method according to claim 1, wherein extraction is performed at a pH in the range of 4 to 5.

6. The method according to claim 1, wherein extraction step (i) comprises mixing the heat coagulated potato protein composition with extraction solvent at a concentration of 80-150 g/L.

7. The method according to claim 1, wherein extraction step (i) is performed at a temperature below the boiling point of the alcohol/water mixture.

8. The method according to claim 4, wherein an extraction solvent comprising 50-70 v % IPA is used at a pH in the range of 4-6.

9. The method according to claim 3, wherein an extraction solvent comprising 60-85 v % Ethanol is used at a pH in the range of 4-6.

10. The method according to claim 1, wherein the method comprises at least two consecutive extraction steps using said alcoholic extraction solvent.

11. The method according to claim 1, wherein said one or more extraction step(s) is/are performed in a continuous process or a batch wise process.

12. The method according to claim 1, wherein steps (i), (ii) and (iii) are performed on heat coagulated potato protein having a mean particle size distribution (d50) between 20 and 300 μm, as determined on a dry product.

13. The method according to claim 1, wherein the method does not comprise adjusting the pH of the extracted heat coagulated potato protein to a value of 6.5 or higher.

14. A purified coagulated potato protein product comprising: less than 100 ppm triglycoalkaloid (TGA) based on dry solids, and less than 0.3% lipids based on dry solids.

15. The purified coagulated potato protein product according to claim 14, having a protein concentration of at least 88% as determined by Kjeldahl.

16. The purified coagulated potato protein product according to claim 14, having: a d10 between 5 and 70 μm, as determined on a dry product; a d50 between 20 and 300 μm, as determined on a dry product; and/or a d90 between 60 and 600 μm, as determined on a dry product.

17-19. (canceled)

20. The method according to claim 2, wherein the extraction solvent comprises ethanol and water at a ratio in the range of 90:10 to 70:30 (v/v).

21. The method according to claim 1, wherein the extraction solvent comprises isopropanol (IPA) and water at a ratio in the range of 90:10 to 50:50 (v/v).

22. The method according to claim 4, wherein an extraction solvent comprising 50-70 v % IPA is used at a pH in the range of 4-6 and at a temperature of 20 to 50° C.

23. The method according to claim 3, wherein an extraction solvent comprising 60-85 v % Ethanol is used at a pH in the range of 4-6 and at a temperature of 20 to 50° C.

24. The method according to claim 1, wherein steps (i), (ii) and (iii) are performed on heat coagulated potato protein having a mean particle size distribution (d50) between 25 and 250 μm, as determined on a dry product.

25. A purified coagulated potato protein product comprising: less than 80 ppm triglycoalkaloid (TGA) based on dry solids; and less than 0.2% lipids based on dry solids.

26. The purified coagulated potato protein product according to claim 14, having: a d10 between 10 and 60 μm, as determined on a dry product; a d50 between 25 and 250 μm, as determined on a dry product; and/or a d90 between 150 and 500 μm, as determined on a dry product.

Description

EXPERIMENTAL SECTION

[0051] Method: Washing coagulated potato protein with alcohols on the laboratory scale. A typical heat coagulated potato protein product, derived from a single batch, was used as starting material in a purification method involving a variety of different extraction regimes. This batch was produced essentially as described in EP0839003 B1, page 1, lines 22-31, and marketed by Avebe under the trade name Protamyl as potato protein for feed. A particular batch used for the experiments was characterized by a dry solids (DS) content of 91.5%, a protein content of 83.4% on DS, a TGA content of 1774 ppm and a lipid content of 3.0% on DS.

[0052] All protein extraction and washing steps were carried out in 0.5 L glass bottles, using a sample volume of 400 ml, with a protein solid content of 90-120 g/L, unless indicated otherwise. Each experiment involved one or two consecutive wash steps, where the alcohol-to-water ratio was indicated as vol:vol. pH values of the suspensions were adjusted to the appropriate levels using either 5 M HCl or NaOH as recorded by a freshly calibrated pH meter (WTW Inolab).

[0053] Alcohols were either isopropanol (GPR RECTAPUR®, VWR Chemicals), 1-propanol (EMPLURA®, Merck) or ethanol (Technisolv, VWR).

[0054] The temperature of the extractions was controlled in a temperature-controlled shaking water bath. Following the one or two alcohol/water washing steps, either one or two final washing steps were done with water, at a protein concentration of 10 wt. % in demi water, which was then incubated for at the same temperature as the alcohol/water washing steps, resulting in totally three washing steps. After each washing step, the protein solids were recovered by centrifugation in a Heraeus Multifuge 1S-R (10 min at 4,000 rpm at room temperature) and the liquid was removed by decanting. Washed protein products were dried in a stove for 2-3 days at 50° C., until a moisture content of <10% was reached. The obtained protein powders were subjected to crude lipid, TGA and protein analyses, as described in the methods section. The analytical values reported are all calculated as percentage or mg/kg (ppm) based on dry matter.

[0055] Analysis of the composition of the protein products was done according to standard procedures.

[0056] TGA levels were determined by online SPE-HPLC as described by Laus et al., (Laus et al, Food Anal. Methods 2017, 10, 845-853; Improved extraction and sample clean up of tri-glycoalkaloids α-solanine and α-chaconine in non-denatured potato protein isolates. https://doi.org/10.1007/s12161-016-0631-2), using commercial standards of α-solanine (Sigma-Aldrich, Germany) and α-chaconine (Carl Roth GmbH, Germany).

[0057] Crude fat (lipids) content was determined by Soxhlet extraction after acid hydrolysis, using petroleum ether and gravimetric detection (according to EG 152-2009).

[0058] Dry solid contents were determined by thermogravimetry, using a Mettler Toledo HR83 Moisture Analyzer device.

[0059] Protein contents were determined by Kjeldahl nitrogen analysis, essentially as described in ISO 3188:1978, using L-tryptophan as standard. The conversion factor used was N*6.25.

[0060] The experimental conditions and the resulting compositions are shown in the following examples.

EXAMPLE 1

Influence of pH on Extraction Efficiency

[0061] This example shows that by using 100% IPA in a purification method at ambient temperature according to NL7500083, lipids are removed only partially and the TGA level is still much too high. It further shows that by using a mixture of IPA and water and adapting the pH of the extraction solvent according to the present invention, both the extraction of lipids and TGA can be optimised. The results are shown in Table 1. At 60% IPA, optimised conditions were found at pH 4-5.

TABLE-US-00001 TABLE 1 TGA Kjeldahl N ppm crude fat protein pH % IPA temp % DS % on DS on DS % on DS Protamyl As is 100 ambient 94.2 84.6 998  2.1 Protamyl As is  90 ambient 92.3 88.5 584  0.2 Protamyl 3  90 ambient 95.2 89.0  90  0.1 Protamyl 3  60 ambient 96.3 84.9  64 <0.1 Protamyl 4  60 ambient 95.0 88.1  27 <0.1 Protamyl 5  60 ambient 94.8 88.7  23 <0.1 Protamyl 6  60 ambient 95.8 91.3  71  0.2

EXAMPLE 2

Influence of Alcohol/Water Ratio on Extraction Efficacy

[0062] Table 2a shows the influence of the alcohol/water ratio of the extraction solvent when extractions are performed at pH 3. At 30% IPA, TGA is removed efficiently, but lipids are not. At 60% IPA, both TGA and lipids are extracted efficiently. At 90% IPA, the efficacy of TGA removal reduces again.

TABLE-US-00002 TABLE 2a TGA Kjeldahl N ppm crude fat protein pH % IPA temp % DS % on DS on DS % on DS Protamyl 3 30 ambient 95.6 83.7 <14  3.1 Protamyl 3 60 ambient 96.3 84.9  64 <0.1 Protamyl 3 90 ambient 95.2 89.0  88  0.1
Table 2b shows the influence of the alcohol/water ratio when extractions are performed at pH 6. Above 40% IPA, both TGA and lipid extraction are performed efficiently. At 90% IPA, the upper limit regarding efficient removal of TGA is achieved.

TABLE-US-00003 TABLE 2b TGA Kjeldahl N ppm crude fat protein pH % IPA temp % DS % on DS on DS % on DS Protamyl 6 30 ambient 94.6 86.7 151 1.9 Protamyl 6 40 ambient 96.0 88.9  96 1.5 Protamyl 6 50 ambient 94.2 92.0  86 0.4 Protamyl 6 60 ambient 95.8 91.3  71 0.2 Protamyl 6 90 Ambient 92.3 88.5 284 0.2
Table 2c shows the influence of the alcohol/water ratio when extractions are performed at optimised pH 4. Similarly to pH 6, extraction mixtures comprising at least 40% IPA are advantageously used for efficient removal of both lipids and TGA.

TABLE-US-00004 TABLE 2c TGA Kjeldahl N ppm on crude fat protein pH % IPA temp % DS % on DS DS % on DS Protamyl 4 40 ambient 96.0 87.7 30  1.4 Protamyl 4 60 ambient 95.0 88.1 27 <0.1

EXAMPLE 3

Influence of Temperature on Extraction Efficacy

[0063] Table 3 shows that at increased temperature, similar results were obtained confirming the excellent extraction conditions to remove TGA and lipids from potato protein when using a mixture of IPA and water at 60% IPA at pH 4 to 5.

TABLE-US-00005 TABLE 3 TGA % Kjeldahl N ppm on crude fat protein pH IPA temp % DS % on DS DS % on DS Protamyl 6  60 ambient 95.8 91.3  71  0.2 Protamyl 6  60 50° C. 92.3 91.9  72 <0.1 Protamyl 5  60 50° C. 93.6 90.1  26 <0.1 Protamyl 3  60 50° C. 95.5 86.1  68 <0.1 Protamyl 3  30 80° C. 96.7 80.7 <14  2.4 Protamyl 6  30 50° C. 92.7 88.1 116  1.7 Protamyl As is 100 70° C. 93.3 87.0 905  0.5
As can be derived from Table 3, despite the elevated temperature, 100% IPA still does not remove TGA and lipid to the desired levels. Again, 30% IPA solvents indicate the lower concentration range as also at higher temperatures this does not remove TGA and more specifically lipid to the desired levels.

EXAMPLE 4

Influence Other C.SUB.1.-C.SUB.4 .Alcohols on Extraction Efficacy

[0064] Table 4 demonstrates that aqueous mixtures with C.sub.1-C.sub.3 alcohols other than IPA also result in the desired reduction in both TGA and lipid content.

TABLE-US-00006 TABLE 4 TGA 60% Kjeldahl N ppm crude fat protein pH Solvent temp % DS % on DS on DS % on DS Protamyl 6 Ethanol ambient 95.8 89.4 62  0.8 Protamyl 6 1-propanol ambient 96.0 91.5 52 <0.1 Protamyl 6 IPA ambient 95.8 91.3 71  0.2

EXAMPLE 5

Extraction Using EtOH/Water Extraction Solvent

[0065] The effect of a single extraction with an extraction solvent consisting of 60, 70, 80 or 90 v % in water on the removal of fat (lipids) and TGA was assessed. Also, a single and a double extraction with EtOH/water (50:50% by volume) was performed (comparative example). All tests were carried out at pH 6 and at ambient temperature. Protamyl containing 1176 ppm TGA and 2.2 wt % lipids (fat) was used as starting material. The results are shown in Table 5.

TABLE-US-00007 TABLE 5 Overview of the effect of ethanol % on fat and TGA removal and total protein content. All tests consisted of one or two consecutive ethanol/water extraction steps, followed by one or two water wash steps (1 h each). TGA fat % % TGA % fat % protein EtOH steps DS P %.sup.DS ppm.sup.DS removal %.sup.DS removal Protamyl 50 1 94.0 84.4  114 90  2.2  0 Protamyl 50 2 90.7 89.0  53 95  1.7  24 Protamyl 60 1 93.2 88.4  118 90  1.1  50 Protamyl 70 1 92.4 88.6  130 89  0.2  90 Protamyl 80 1 92.6 88.5  134 89 <0.1 >95 Protamyl 90 1 92.8 89.3  197 83  0.1  95 Protamyl as is 90.0 82.2 1176 —  2.2 —
No fat removal was measured after extraction with 50v % ethanol in water, At 60v %, the performance was increased, while at 70v % and higher, a single extraction step was sufficient to remove fat to the desired level of 0.2% or lower. The efficiency of fat removal increased with ethanol concentration and was optimal at 80%.
Regarding TGA removal, the ethanol concentrations had very similar performance for the range of 50-80%; all removed 89-90% of the TGA, while washing with 90v % ethanol gave a slightly worse performance. A single ethanol wash at 50-80v % was enough to reach a TGA level below 150 ppm, but only with a EtOH-to-water ratio in the range of 90:10 to 60:40 both the TGA and lipid content were reduced to a desirable level.

EXAMPLE 6

Particle Size Distribution of Representative Starting Materials and Purified Potato Protein Coagulates

[0066] This example illustrates the typical particle size distribution of representative starting material, as well as that of purified potato protein coagulates obtainable by an extraction method of the invention.

[0067] Extractions were performed using an alcoholic extraction solvent as described in the Experimental section herein above, except that all extractions were carried out at a larger scale in 5 L glass beakers equipped with stirrer at sample volumes of 2.5 L and a protein solid content of 100 g/L. After two consecutive extraction steps of 1 hour each at pH 6 and ambient temperature using the alcohol/water extraction solvent, a final washing step with water during 1 hour at a protein solid concentration of 100 g/L was performed.

[0068] The washed protein products were resuspended in tap water to a dry solid concentration of 10 wt % and subsequently dried with an Anhydro Compact spray drier (Copenhagen, Denmark) using a rotary disk nozzle at a rotating speed of 30.000 rpm. The inlet temperature is 175° C. and the outlet temperature was 75° C. The particle size distribution (PSD) of the final dried powder was assessed in either the dry and wet state. Every PSD value shown in the tables below is the result of two measurements.

Particle size distribution of starting material, intermediate or final product was determined using laser diffraction, and the particle size data were calculated with the Frauenhofer method. The software used for performing this calculation is WINDOX 5.6.2.0, HRLD.
Wet particle size distribution was measured by a laser diffraction on a Sympatec HELOS equipped with a Quixel wet dispenser. To that end, a dry sample was added to a water-filled sample chamber until a laser obscuration level in the range of 10 to 25% was obtained. The measurement was carried out for the duration of approximately 20 seconds at 25° C.±2° C. The cuvette had a size of 6 mm.
Particle size distribution of dry potato protein samples was measured by laser diffraction using a Sympatec HELIOS equipped with a RODOS dry dispenser with a vibratory feeder. The RODOS dispersing line has an inner diameter of 4 mm.

TABLE-US-00008 TABLE 6 Analysis of three representative potato protein coagulate starting materials. Protamyl 1 Protamyl 2 Protamyl 3 PSD “wet” d 10 (μm) 86.6 36 44 d 50 (μm) 250.8 137.4 159.1 d 90 (μm) 650.7 321.5 498 PSD “dry” d 10 (μm) 80.45 29.55 32.85 d 50 (μm) 193.1 114.5 138 d 90 (μm) 493 284.5 416

TABLE-US-00009 TABLE 7 Analysis of two representative purified potato protein coagulate products. Protein starting material Extraction Protamyl Protamyl solvent medium v % 60% IPA 80% EtOH nr wash steps 2 2 d.s. wt % 95.8 94.1 KjeldahlN % on DS 91.3 90 TGA ppm on DS 71 69.1 crude fat % on DS 0.2 <0.1 PSD “wet” d 10 (μm) 14.3 41.1 d 50 (μm) 69.2 160.4 d 90 (μm) 271.5 397.5 PSD “dry” d 10 (μm) 13.5 32.7 d 50 (μm) 62.4 128.4 d 90 (μm) 294.6 335.7