WO2019011976A1

WO2019011976A1 - Method for extracting salt from a composition comprising organic matter

Info

Publication number: WO2019011976A1
Application number: PCT/EP2018/068774
Authority: WO
Inventors: Johan Pieter Marinus Sanders; Koen Peter Henri Meesters
Original assignee: Stichting Wageningen Research
Priority date: 2017-07-11
Filing date: 2018-07-11
Publication date: 2019-01-17
Also published as: NL2019228B1

Abstract

The present invention relates to a method for extracting salt and optionally one or more organic compounds from a composition comprising organic matter, and in particular from a dry or solid composition comprising organic matter. The present invention further relates to the use of the extracted salt and optionally one or more organic compounds, and/or of the remaining organic matter, for preparing foodstuff, a fertilizer, animal feed and/or a chemical.

Description

METHOD FOR EXTRACTING SALT FROM A COMPOSITION COMPRISING

ORGANIC MATTER

The present invention relates to a method for extracting salt and optionally one or more organic compounds from a composition comprising organic matter, use of the salt and optionally one or more of the organic compounds for preparing foodstuff, animal feed, fertilizer and/or chemicals, and use of the remaining composition comprising organic matter for preparing foodstuff, animal feed, fertilizer and/or chemicals.

Salts may be removed from liquid compositions via chromatography (Ion Exchange) and via membrane processes such as electrodialysis or dialysis There are, however, a number of disadvantages associated with these techniques. For instance, regeneration of chromatography materials leads to chemical consumption and produces a diluted salt water stream. Also, membranes may suffer from heavy fouling depending on the properties of the organic matter. This will lead to cleaning costs or replacement of the membranes.

Solid compositions may be desalted via leaching. This method can, however, not be applied if the organic compounds that are to be retained are not sufficiently stable in water (DDGS, dried CSL, etc.) or are soluble in water (such as for instance lactose in whey permeate powder (WPP).

The object of the present invention is to provide an efficient method for desalting material comprising organic matter, in particular dry or solid material comprising organic matter, and recovering the salt for further use while leaving the structure of the non-salt materials intact and undissolved as much as possible. Preferably, the method also allows the recovery of particular organic compounds.

This object is met by providing a method comprising an extraction step using water and a miscible solvent.

Accordingly, the present invention relates to a method for extracting salt from a composition comprising organic matter, wherein the method comprises:

a) contacting the composition with water and a miscible solvent for a period sufficient to dissolve the salt in the liquid phase of the resulting mixture; and

b) separating the liquid phase comprising the salt from the solid phase comprising the organic matter.

This method is referred to herein as "the method of the invention" and is based on the principle that salt is capable of dissolving in water comprising a miscible solvent and that many organic compounds are not. Non-polar molecules, but also polymers and oligomers of polar components, will for instance not dissolve in such a mixture. Certain organic compounds, such as for instance citric acid, fructose, glutamic acid, valine and zein, may also dissolve in water comprising a miscible solvent and can therefore be extracted in conjunction with the salt. This depends largely on the solvent used, temperature and pH during the extraction process. For instance, higher temperatures generally result in a better solubility but may also affect the compound to be extracted. The pH is preferably chosen such that it is close to the isoelectric point of the compound, as this increases its solubility in the organic phase. The salt and optionally one or more organic compounds are thus removed from the starting material and can be recovered for further use. After the method of the invention has been applied, the composition comprising organic matter has a reduced level of salt and optionally of one or more particular organic compounds. As such, it is more suitable for application in the foodstuff and/or animal feed industry, as well as in the production of chemicals.

The composition comprising organic matter, and undesired salts, may be any composition comprising organic matter. However, the method of the present invention is in particular applicable to removing salt and optionally one or more organic compounds from foodstuff, one or more of the raw materials used for producing foodstuff or in particular baby food, such as for instance whey permeate powder, potato fiber, and beet pulp, animal feed, one or more of the raw materials used for producing animal feed, such as for instance sunflower cake, rapeseed cake, corn steep powder, potato steam shells, dextrose, plant stalks, distiller's dried grains with solubles (DDGS), potato flakes, whey permeate powder (WPP), meadow grass, fermentation broth, and yeast extract powder, and waste residues, such as for instance verge grass. Products, or intermediate products, of enzymatic or chemical conversions in which salts are required or are formed, such as for instance the enzymatic production of disaccharides or oligosaccharides from sucrose wherein glucose- 1- phosphate is an intermediate, may also be used.

The method of the present invention is particularly useful because it allows the extraction of salt and optionally one or more organic compounds from dry or solid compositions. A dry or solid composition preferably comprises more than 60 wt.%, more than 65 wt.%, more than 70 wt.%, more than 75 wt.%, more than 80 wt.%, more than 85 wt.%, more than 90 wt.%, or more than 95 wt.% dry matter.

Compositions intended to be subjected to the method of the present invention, such as for instance foodstuff and animal feed, often comprise hygroscopic components. Hygroscopic components swell when contacted with water. However, hygroscopic components do not swell, or to a lesser extent, when a water/solvent mixture in accordance with the present invention is used during the extraction process. This means that extracting equipment with smaller dimensions will be sufficient, thereby saving on energy and capital. Also the physical structure of dried and pelletized compositions subjected to the extraction process will remain intact, whereas the compositions would disintegrate when too high levels of water are used. This way the liquid can easily flow through the solid particles and the solids are easily separated from the liquid.

The solvent should be miscible with water and is preferably an organic solvent. Preferably, the organic solvent is selected from the group consisting of an alcohol, in particular ethanol, propanol, isopropanol, butanol, isobutanol, n-pentanol, 2-pentanol or 3-pentanol, a diol, in particular ethylene glycol or 1,3 -propanediol, a polyol, in particular glycerol, a ketone, in particular acetone, propanone, butanone or pentanone, an ester, in particular ethyl acetate, and any combination of the foregoing.

In general, the solvent and its concentration should be selected in such a way that salts present in the starting composition dissolve in the resulting liquid phase of the resulting mixture. In addition, the solvent may be chosen such that certain organic compounds also dissolve in the liquid phase of the resulting mixture. Other small organic components, however, such as for instance lactose which is valuable as part of the remaining organic matter, should be prevented from dissolving in the liquid phase of the resulting mixture. It is further preferred that most or all of the organic matter remaining in the solid phase of the resulting mixture retains its physical structure. Solvents that lead to these results can readily be determined by those of skill in the art.

It is important that the mixture of water with solvent forms a single phase. This can be established by selecting suitable water : solvent ratios and elevated temperatures. Suitable water : solvent ratios can readily be determined by a person skilled in the art using routine

experimentation. The concentration of the solvent should at least be as low as is required to prevent the formation of a second phase. No second phase is to be formed, not even after the salt is dissolved. Alternatively, ternary mixtures or more complex mixtures such as a mixture comprising ethanol, ethyl acetate and water, may be used to keep the mixture in a single phase.

One may take the relative permittivity of the resulting water/solvent mixture into consideration when certain fibrous materials are subjected to the extraction method of the present invention. For instance, if the starting material comprises dried CSL pellets or DDGS, the relative permittivity of the water/solvent mixture should be lower than 40, more preferably lower than 35, even more preferably lower than 30. The lower boundary depends on the type of solvent being used. The relative permittivity of a water/ethanol mixture is preferably 20 or higher. The relative permittivity of a water/isopropanol mixture is preferably 18 or higher. The relative permittivity of a water/butanol mixture is preferably 18 or higher. The relative permittivity of a water/pentanol mixture is preferably 14 or higher. The relative permittivity of a water/acetone mixture is preferably 21 or higher. The relative permittivity of a water/pentanone mixture is preferably 15 or higher. The relative permittivity of a water/ethyl acetate mixture is preferably 6 or higher. The relative permittivity can be adjusted by selecting more or less non-polar compounds and using different ratios.

The present inventors have found that ethanol is particularly suitable as a solvent, especially when the ratio water : ethanol is between 10 : 90 and 40 : 60. This mixture is particularly suitable for extracting salt and optionally one or more organic compounds from WPP, CSL pellets and DDGS.

The temperature at which the extraction is performed is between room temperature and about 5°C below the boiling point of the solvent, such as for instance between room temperature and about 73.4°C for ethanol, between room temperature and about 92.1°C for propanol, between room temperature and about 77.0°C for isopropanol, between room temperature and about 112.3°C or 94.5 °C for butanol, between room temperature and about 61 °C for acetone, between room temperature and about 97°C for pentanone, and between room temperature and about 72.1 °C for ethyl acetate.

The pH at which the extraction is performedis lower than 11 to avoid swelling of the fibres, and preferably between 3 and 11.

When the liquid phase comprising the salt and optionally one or more organic compounds is separated from the solid phase comprising the remaining organic matter, subsequent steps may be performed to recover the salt and optionally one or more organic compounds for future applications. The method may therefore further comprise a step of distilling the liquid phase to remove the solvent, thereby obtaining a concentrate comprising the salt and optionally one or more organic compounds. Certain organic compounds may subsequently be precipitated from the concentrate because they do not dissolve in water comprising a high salt concentration. Some organic compounds are capable of dissolving in water comprising a high salt concentration and will remain in the concentrate, whereas other organic compounds may evaporate during the distilling step. The liquid phase of the concentrate then only still comprises the salt and optionally any organic compound that does dissolve in water comprising a high salt concentration and has not evaporated during the distillation. Also, inorganic compounds may still be present in the liquid phase of the concentrate. These inorganic compounds may be removed if the application of the recovered salt and optionally the one or more organic compounds so requires. For instance, potassium may be removed by adding (NH^SC^ and phosphate and phytic acid may be removed by adding Ca(OH)₂ or Mg(OH)2. The K₂S0₄ and KMgP0₄ that precipitate during this process may be used for certain applications, such as for instance as part of a fertilizer.

Alternatively, the salt and optionally one or more organic compounds present in the liquid phase after the initial extraction may be extracted by a second extraction step instead of the above distilling and precipitation process. Also, when the liquid phase comprising the salt and optionally one or more organic compounds is separated from the solid phase comprising the organic matter, subsequent steps may be performed on the solid phase. The method may therefore further comprise a step of drying the solid phase to remove any remaining water and/or solvent, thereby obtaining a solid mixture. Another extraction step may be added if any particular organic material is to be recovered from this solid mixture. For instance, high quality proteins can be recovered from the other components by adding a solution comprising NaOH or NH₄OH to the solid mixture. The resulting filtercake may for instance be used as part of an animal feed.

The extraction steps in the method of the present invention may be performed by means of any extraction method, however, a counter current extraction is preferred. In a counter current extraction, the liquid phase resulting from the extraction is passed over the remaining composition comprising organic matter. This is repeated one or more times. The counter current principle ensures that most of the salt and optionally most of the one or more specific organic compounds are removed from the starting material, and results in a highly concentrated end product. Less extraction liquid is thus needed for obtaining a high concentration of salt and optionally a high concentration of the one or more organic compounds. This will lead to lower capital investments and decreased energy input. The method of the present invention results in a higher yield and concentration of salts and organics while saving on energy and capital.

The salt and optionally one or more organic compounds extracted and recovered by the method of the present invention can be used in several applications. Potassium salts, such as for instance KC1, K O₃, KH2PO4, and K2SO4, and mixtures of anions may for instance be added to foodstuff in order to improve its taste. This can be done in a controlled manner so as to keep any negative health effects under control. The salts and mixtures of anions may also be used as, or as part of, animal feed and fertilizers. Organic compounds, such as amino acids and salts thereof, carbohydrates, and organic acids and salts thereof may be added to foodstuff and/or animal feed to influence its taste, texture, nutritional and/or health benefits. The organic compounds may also be used in the preparation of chemicals.

The remaining organic matter, i.e. the organic matter comprising a reduced level of salt and optionally reduced level of one or more organic compounds obtained by the method of the present invention, can also be used in several applications. It may for instance be used as, or as an ingredient of, foodstuff and/or animal feed, or in the production of chemicals. It is particularly useful as, or as part of, foodstuffs for human consumption as it comprises a lower concentration of salt which is associated with a lower risk of health issues. It is further particularly useful as part of an animal feed, as raw materials having a lower salt concentration can be mixed with other ingredients containing high concentrations of salt in order to not exceed the overall limits of salt intake of the animals.

EXAMPLES

EXAMPLE 1

4 gram of whey permeate powder (WPP) was incubated at 25°C in 10 ml of water/ethanol mixtures comprising 90%, 80%, 70%, and 60% of ethanol during 60 minutes.

The liquid was separated from the solids by means of filtration. The filtercake was dried at

100°C during 60 minutes and the recovery of the dry matter was measured being above 95% w/w in all mixtures. From this it can be concluded that the lactose which constitutes about 88% w/w of the initial composition is not significantly dissolved in any of the solvent compositions.

The dried filtercake was dissolved in 50 ml of water and the conductivity was measured with a Hanna DIST 4 conductometer. As a control, 4 gram of untreated WPP was dissolved in 50 ml water.

The control WPP (whey permeate powder) contained 212 mg/4 gram of NaCl equivalents, as concluded from a calibration curve made with a conductometer. The filtercake still contained 180, 160, 115 and 80 mg per 4 gram of NaCl equivalents. This means that 15, 25, 46 and 63% w/w of NaCl respectively has been removed by the solvent mixtures mentioned above.

The salt removed with the water phase present in the solvent mixtures was in the range of 26-33 mg of NaCl equivalents per ml.

These results show that a mixture of water and ethanol can be used to extract salt from a dry composition. These results further demonstrate that an increase in the water : alcohol ratio increases the amount of salt that is extracted.

EXAMPLE 2

4 gram of WPP was incubated in a 10 ml ethanol water mixture comprising 80% ethanol as described in EXAMPLE 1 but now at 40°C, as well as at 60°C.

Following the same procedures as in EXAMPLE 1, 65 and 74 mg NaCl salt equivalents were extracted respectively. This is 25 and 42 % higher than when the extraction was performed at 25°C. EXAMPLE 3

Meadow grass was macerated by a Andritz refiner. The macerated material was oven dried to 85% dry weight. 4.13 gram of this material was mixed with 38 gram of a water/ethanol mixture comprising 96% v/v ethanol and incubated for 1 hour at room temperature.

The liquid was decanted and the remaining fibrous material was dried at 105° C during 1 hour.

The dried remaining fibrous material was mixed in 40 ml of water and equilibrated overnight at room temperature. Also, as a control 3.2 gram of dried macerated grass was incubated overnight in water. The conductivities were determined at 2.89 mS for the treated material and 6.46 mS for the untreated control material, corrected for the conductivity of tap water that was used.

55% of the NaCl equivalents of the grass salts have thus been extracted by this procedure.

EXAMPLE 4

Corn steep liquor (CSL) is dried by industry to a pellet form and used in compound feed mixtures. The pellets disintegrate easily when brought into contact with water.

14 gram of CSL pellets are soaked in 40 ml of water. After 3 minutes all the water is taken up by the pellets and no free water is present.

14 gram of CSL pellets are soaked in a total volume of 100 ml of water and incubated for

15 minutes at room temperature. The mixture is put on a paper filter and after 15 minutes a filtrate of 15 ml is obtained. After 30 minutes, about 40 ml filtrate is obtained while still about 10 ml free water is associated with the filtercake.

This shows that the original structure of the CLS pellets has completely disappeared when dissolved in water.

14 gram of CSL pellets are soaked in a total volume of a 50 ml water/ethanol mixture comprising 87% v/v ethanol. The pellets were not disintegrated after 1 hour of incubation. The soaked pellets are filtered off and 23 ml of filtrate is obtained.

The filtercake is incubated for a second time by addition of a fresh 23 ml water/ethanol mixture comprising 87% ethanol for 24 hours. The filtercake did not disintegrate. The filtercake was filtered off and 23 ml of volume was obtained as the filtrate. The filtercake was incubated for a third time by adding a 25 ml water/ethanol mixture comprising 87% ethanol during 12 hours and filtered off to obtain 24 ml of filtrate. The filtercake was dried at 105°C for 1 hour and the weight was determined at 14.5 gram. The salts in the filtercake were determined by conductivity after dissolving the filtercake in 100 ml of water. While a fresh batch of CSL pellets contains 25 gram of salt equivalents per kg dry matter, the 3 times extracted filtercake still contains 16 gram of salt equivalents per kg dry matter. Per gram of water in the extracting solvent mixture, 21 mg of salt has been removed, at a concentration of about 0.33M of NaCl equivalents.

This shows that with use of a water/ethanol mixture, salt can be extracted from dried CSL pellets while leaving the physical structure of the CSL pellets intact. EXAMPLE 5

15 gram of CSL pellets were soaked in a 20 ml water/ethanol mixture comprising 80% v/v ethanol and the absorption rate of the solvent mixture was measured in time by measuring the free liquid present.

15 gram of CSL pellets were soaked in a 20 ml water/isopropanol mixture comprising 80% v/v isopropanol and the absorption rate of the solvent mixture was measured in time by measuring the free liquid present. The results are shown in Table 1.

Table 1. Volume of absorbed liquid in ml.

These results indicate that the absorption rate is lower in a water/isopropanol mixture comprising 80% v/v isopropanol than in a water/ethanol mixture comprising 80% v/v ethanol.

EXAMPLE 6

2 grams of dried seaweed Saccharina latissima having a dry weight of 86% and an ash content of 42% is extracted three times with 15 ml water/ethanol mixtures comprising 87% v/v ethanol. The filtercake is dried at 105°C during 1 hour. The filtercake is subsequently dissolved in 90 ml of tap water and the conductivity measured. The conductivity is determined to be 3.4 mS. The conductivity of the control was determined at 9.5 mS. 62% of the salt equivalents has thus been removed.

According to the conductivity curve that was calibrated against NaCl, the dissociated salt composition in the original seaweed material is 21%. The difference between 21 and 42% probably is sand or other ash material without conductivity, such as not dissociated salts.

Claims

1. Method for extracting salt from a composition comprising organic matter, wherein the method comprises:

2. Method according to claim 1, wherein one or more organic compounds are co-extracted with the salt.

3. Method according to claim 1 or 2, wherein the composition comprising organic matter is selected from the group consisting of foodstuff, raw materials used for producing foodstuff, animal feed, raw materials used for producing animal feed, fermentation broth and waste material.

4. Method according to any one of claims 1-3, wherein the composition comprising organic matter is a dry or solid composition.

5. Method according to any one of claims 1-4, wherein the solvent is miscible with water and is preferably an organic solvent, which is preferably selected from the group consisting of an alcohol, in particular ethanol, propanol, isopropanol, butanol, isobutanol, n-pentanol, 2- pentanol or 3-pentanol, a diol, in particular ethylene glycol or 1,3 -propanediol, a polyol, in particular glycerol, a ketone, in particular acetone, propanone, butanone, 2-pentanone or 3- pentanone, an ester, in particular ethyl acetate, and any combination of the foregoing.

6. Method according to any one of claims 1-5, wherein the solvent is ethanol and the ratio water : alcohol is between 10 : 90 and 40 : 60.

7. Method according to any one of claims 1-6, further comprising precipitating one or more organic compounds from the liquid phase comprising the salt and one or more organic compounds resulting in a precipitate comprising the one or more organic compounds and a liquid phase comprising a high salt concentration.

8. Method according to any one of claims 1-6, further comprising distilling the liquid phase to remove the solvent, thereby obtaining a concentrate comprising the salt and optionally the one or more organic compounds, and/or distilling the solid phase to remove any remaining water and/or solvent, thereby obtaining a solid mixture.

9. Method according to claim 8, further comprising precipitating one or more organic

compounds from the concentrate resulting in a precipitate comprising the one or more organic compounds and a liquid phase comprising a high salt concentration.

10. Method according to claim 9, further comprising using the precipitated one or more organic compounds as an ingredient in the preparation of foodstuff, animal feed and/or a chemical.

11. Method according to claim 9 or 10, further comprising precipitating one or more salts from the liquid phase comprising a high salt concentration.

12. Method according to claim 11, further comprising using the precipitated one or more salts as an ingredient in the preparation of foodstuff, animal feed and/or a chemical.

13. Method according to claim 8, further comprising extracting one or more organic

compounds from the solid mixture.

14. Method according to any one of claims 1-6, wherein the method is a counter current extraction.

15. Method according to claim 13, wherein the extraction is a counter current extraction.

16. Use of salt and optionally of one or more organic compounds obtainable by the method according to any one of claims 1-15 for preparing foodstuff and/or a fertilizer and/or animal feed and/or a chemical.

17. Use of the organic matter obtainable by the method according to any one of claims 1-15 for preparing foodstuff and/or animal feed, or in the production of a chemical.