CA2600091A1 - Maple syrup production - Google Patents

Abstract

A method is provided herein for making maple syrup from a maple sap. The method includes the essential step of flowing a stream of maple sap along a supporting non-porous surface, either in countercurrent or co-current flow to an air stream whose maximum temperature is about 20 -25 degrees C. This flow ids continued until maple syrup having the desired Brix number ( e.g. of 61 +/ 0.5 ) is obtained..</SD OAB>

Description

= CA 02600091 2007-08-31 MAPLE SYRUP PRODUCTION
FIELD OF THE INVENTION

[0001] This invention is directed to processes for the production of high quality maple syrup.

BACKGROUND OF THE INVENTION
DESCRIPTION OF THE PRIOR ART

[0002] In the northern United States and Canada, the sap of hard maple trees (Acer Saccharinum) is a source of sugar, largely sucrose, but containing impurities that impart a delicate flavor. Maple sap containing 2-3% sugar as it comes from the tree has no maple flavor and no color. The characteristic flavor and maple color result from reactions that occur when maple sap is evaporated and concentrated to the syrup form by boiling. For conventional maple sugar production, concentration is carried to the graining point to produce a soft brown "whole sugar," that is, the syrup and sugar crystals are allowed to form a solid mass without separation.

[0003] Commercial maple syrup typically has about a 66degree Brix with water activity of 0.83-0.85 and is very susceptible to yeast and mold contamination.
Also, since maple syrup is readily fermentable, it must be stored under very restricted conditions.

[0004] The evaporation of sap in the production of maple syrup is usually made in horizontal pans provided with partitions and heated with wood logs. The vapor produced is usually lost in the atmosphere. Some attempts have been made to use the heat lost by the vapor which rises over the flat horizontal pans.

[0005] It is known that maple syrup containing at least about 63% sucrose to a solids content of about 93 to about 98% may be prepared by several alternative concentration steps. The maple sap may be heated at a temperature in the range of about 162 to about 196.degrees F at about 19 to about 27 inches Hg vacuum, to produce a concentrate form of maple syrup which is alleged to have minimal color changes. Alternatively, the I

concentration may be carried out in two stages. In the first stage the maple sap may be heated to a temperature in the range about 162 to about 196 degrees F at aboutl9 to about 27 inches Hg vacuum until the solids content of the maple syrup is at least 90%. In the second stage, the maple syrup may be further concentrated by heating at a temperature in the range about 250 to about 265 degrees F at atmospheric pressure until the solids content is in the range of about 93 to about 98 %. The color of the concentrate so prepared is slightly darker than the original color of the syrup. Finally, the concentration may be carried out at atmospheric pressure at a temperature in the range of about 250 to about 265 degrees F to produce a concentrate which was darker than the original syrup.

[0006] In addition to the above general prior art, some prior art patents which relate to the production of maple syrup and/or maple sugar include the following:

[0007] U.S. Patent No 5,389,209, patented Feb 14, 1995 by Y.A. Paquette "Production of High Quality Maple Syrup" provided a process which was alleged to make a light color maple syrup from a water-containing maple sap. In a first step, the maple sap was boiled under normal pressure to evaporate part of the water contained therein in the form of steam, to form a maple syrup and to develop caramelized and sweet characteristics and give flavour and a tinted color to this maple syrup. In a second step, the maple sap was heated at a temperature lower than the boiling temperature of the maple sap and was atomized through an air circulating column to evaporate another part of the water contained therein. This second step which could be carried out before the first step, was alleged to permit concentration of the maple sap, to increase its sugar content and to avoid further caramelization thereof. The maple sap, which was so obtained with increased sugar content, may be recycled as long as necessary until a desired sugar concentration corresponding to a predetermined Brix number was reached.

[0008] U. S. Patent No 4,159,210 patented Jun 26, 1979 by A. C. C. Chen et al "Maple Sugar Product and Method of Preparing and Using Same' provided a transformed, crystallized maple sugar product comprising aggregates of crystals having a crystal size in the range about 3-50 microns which was prepared by concentrating a maple syrup containing at least about 63 % sucrose to a solids content of about 93-98 %.

[0009] The concentration was said to be able to be carried out in several ways depending upon the color of the final product which was desired. The concentrated syrup was then subjected to impact beating within a crystallization zone for transformation and crystallization. The resulting transformed, crystallized maple sugar product comprising aggregates of sucrose crystals having a size in the range about 3-50 microns and having a moisture content of 2-4% was then recovered from the crystallization zone and was dried to a moisture content below about 1% by weight. Subsequently, the maple sugar product may be cooled, milled and/or screened to a size range suitable for one of several desired end uses.

DESCRIPTION OF THE INVENTION
AIMS OF THE INVENTION

[00010] A problem with the current procedures for producing maple syrup from maple sap is that heating for concentration thereof often results in excessive carmellization of the maple syrup, which detracted from the natural flavour of maple syrup. The present invention aims to provide improved methods for the production of maple syrup from maple sap.

SUMMARY OF THE INVENTION

[00011] The invention in its general form will first be described, and then its implementation in terms of specific embodiments will be detailed with reference to the drawings following hereafter. These embodiments are intended to demonstrate the principle of the invention, and the manner of its implementation. The invention in its broadest sense and more specific forms will then be further described, and will then be defined in each of the individual claims which conclude this Specification STATEMENTS OF INVENTION

[00012] By a first embodiment of the present invention, a method is provided for making maple syrup from a maple sap, the method comprising: flowing a stream of maple sap along a supporting non-porous surface, either in countercurrent or co-current flow to an air stream whose maximum temperature is about 20 -25 degrees C.
until maple syrup having the desired Brix number is provided.

[00013] Brix as used herein is its standard meaning i.e., a unit of proportion equal to percent to measure the concentration of sugars and other soluble solids in maple syrup.
One Brix =1 %.

[00014] By a second embodiment of the present invention, a method is provided for making maple syrup from a maple sap, the method comprising carrying out ion exchange chromatography in a chromatographic column containing a chromatography ion exchange matrix, thereby to absorb maple syrup thereon and eluting maple syrup from the column by with a maple sap solution which is more concentrated than the original maple sap but is less concentrated than the maple syrup to be produced.

[00015] By a third embodiment of the present invention, a method is provided for making maple syrup from a maple sap, the method comprising carrying out a membrane distillation procedure by contacting a moving stream of maple sap with a selectively liquid porous membrane and recovering maple syrup on a non-porous condenser surface disposed below the selectively liquid porous membrane.

OTHER FEATURES OF THE INVENTION
FEATURES OF THE FIRST EMBODIMENT

[00016] By one variant of this embodiment of the present, the maple sap is atomized in an air circulating column and moves downwardly by gravity through an upward flow of air in a counter-current fashion.

[00017] By a variation of such variant, the air which is fed into said air circulating is outside air, which is preferably at ambient temperature.

[00018] By a second variant of this embodiment of the present, the maple sap is concentrated until a Brix number of 61 +- 0.5 is obtained.

[00019] By a third variant of this embodiment of the present, the maple sap is concentrated until up to about 40% of the water content is removed.

[00020] By a fourth variant of this embodiment of the present, the method for making maple syrup from maple sap includes evaporating at least about 50% by weight of the water contained in the sap by atomization of the maple sap at a temperature up to about 25 deg C in an air circulating column through which air is blown at low pressure and wherein humid air is formed and is eliminated

[00021] By a variation of such variant, evaporation is conducted by circulating the sap in atomized form in counter-current through an airflow channel.

FEATURES OF THE SECOND EMBODIMENT

[00022] By a first variant of this embodiment of the present invention, the ion exchange resin is selected from the group consisting of : an ion exchange resin having an ion which is identical with an ion of highly ionized solute; a cation exchange resin having an acidic form, the cation exchange resin containing sulphonic acid groups or carboxylic acid groups; an anion exchange resin having a basic form, the anion exchange resin containing quaternary ammonium groups or being in sulfate form; an adsorbent comprising alumino silicate or zeolite, e.g. a calcium-Y-type or calcium-X-type zeolite ,and containing one or more selected cations at exchangable cation sites, namely, sodium, barium or strontium ions or cationic pairs, namely barium and potassium or barium and strontium; sulfonated polystyrene divinyl benzene crosslinked ion exchange resins exchanged with calcium ions or ammonium ions; poly (4-vinylbenzeneboronic acid) resins; sulfonated polystyrene cross-linked with divinyl benzene. isoprene, allyl methylacrylate, vinyl methacrylate, glycol methacrylate or glycol diacrylate.
in alkali metal form, sodium being generally the preferred alkali metal; a strong acid cation exchanger preferably in sodium or potassium form; an anion exchange resins in a bisulfite, sulfite form or sulfateform;
an acrylic weakly acid cation exchange resin with a carboxylic functional group cross-linked with from about I to about 20%, preferably from about 3 to about 8%
divinyl benzene, the resin being in hydrogen ion, potassium ion, sodium ion, magnesium ion or calcium ion forms, or other ion forms; and polystyrene matrix resins.

[00023] By a second variant of this embodiment of the present invention, the method is carried out by a chromatographic simulated moving bed (SMB) procedure using an ion exchange resins with a small bead size.

[00024] By a first variation of this variant of this embodiment of the present invention, the chromatographic bed includes a plurality of compartments, each such compartment comprising a section which holds a column filled with the ion exchange resin and which comprises a forepart for distributing the maple sap to the middle part containing such resin and a rear part for collecting water component of the maple sap from this middle part.

[00025] By a second variation of this variant of this embodiment of the present invention, the resin is packed uniformly in compartments so that the resin movement in the compartments is effectively minimized.

[00026] By a third variation of this variant of this embodiment of the present invention, the resin bed has a total resin bed length may be in the range of about 14 to about 24 meters.

[00027] By a third variation of this variant of this embodiment of the present invention, the bead size of the resin is about 300 to about 360 m, or about 220 to about 240 pm or about 100 to about 200 m, or about 125 to about 160 pm, and preferably where about 75% of the beads are within +/-20% range from the mean bead size.

[00028] By a fourth variation of this variant of this embodiment of the present invention, the resin bed has a total resin bed length may be in the range of about 14 to about 24 meters.

[00029] By a second variant of this embodiment of the present invention, the method is continuous or is sequential or is a combination of a continuous method and a sequential method.

[00030] By a third variant of this embodiment of the present invention, the method includes passing the maple sap through a plurality of feed zones containing a section of the chromatographic bed to receive the maple sap, including feeding maple sap into one feed zone or including feeding maple sap into more than one feed zone, or feeding maple sap into all feed zones once during each cycle.

[00031] By a fourth variant of this embodiment of the present invention, the eluant comprises maple sap which is more concentrated that the feed maple sap, preferably where the eluant comprises maple sap which has passed at least once through the chromatographic column.

[00032] By a fifth variant of this embodiment of the present invention, the method is carried out in a chromatographic column is carried out at temperatures from about 10 to about 20.degree C.

FEATURES OF THE THIItD EMBODIMENT

[00033] By a first variant of this embodiment of the present invention, the selectively liquid porous membrane comprises any commercially-available membrane, which is made of PTFE, PVDF, PP or PE, or may be a so-called asymmetric microfiltration membrane made of polyethersulphone, polysulphone, polyacrylonitrile, polyamides. polyolefins (e.g. polyethylene, polypropylene and the like), polysulfone, polyether sulfone, silicone resin or fluororesin preferably where the membrane is polypropylene, polyethylene or polytetraflorethylene, having a pore diameter of between 0.00001 and 0.005 mm, usually between 0.0001 and 0.0005 mm.

[00034] By a first variation of this variant of this embodiment of the present invention, the membrane has a porosity greater than about 70% and preferably greater than about 80% and pore size larger than about 0.1 pm preferably between 0.3 and 1.0 pm, whereby water may pass therethrough.

[00035] By a second variation of this variant of this embodiment of the present invention, the characteristics of the membrane are changed by means of a coating or other surface modification.

[00036] By a second variant of this embodiment of the present invention, the membrane is a flat membrane sheet or plate, optionally in a spirally wound configuration, or plate-like structures consisting of multiple capillary-like channels to limit the flow channels formed from such material as threads or fabric, or which is non-porous.

[00037] By a third variant of this embodiment of the present invention, the membrane comprises a hollow fibre membrane for direct contact membrane distillation to provide compact packing of membrane fibres, thereby providing a relatively large surface area.

[00038] By a first variation of this variant of this embodiment of the present invention, the hollow fibres or capillary membranes are placed in parallel.

[00039] By a fourth variant of this embodiment of the present invention, the method includes providing a gap of predetermined width between the membrane and a condenser surface.

[00040] By a first variation of this variant of this embodiment of the present invention, the method includes providing the width of the gap by using a suitable spacer, preferably made of hydrophobic plastic which is highly porous preferably greater than about 90% and whose thickness determines the width of the gap, preferably where the gap is less than 5 mm, preferably between 0.5 and 2 mm or 0.2 to 1.0 mm.

[000411 By a first variation of this variant of this embodiment of the present invention, the method includes providing the gap at about atmospheric pressure, or includes filling the gap with air hydrogen, helium, carbon dioxide, or nitrogen.

[00042] By a fifth variant of this embodiment of the present invention, the method includes providing a counter-current flow of a warm stream of maple sap feed and the concentrated stream of maple sap.

[00043] By a first variation of this variant of this embodiment of the present invention, the method including providing the feeding a stream of maple sap feed stream through hollow non-porous, non vapour-permeable or barely vapour-permeable fibres/capillaries placed in parallel.

[00044] By a second variation of this variant of this embodiment of the present invention, the method including discharging the concentrated stream of maple sap through a fabric material that has been applied to or around the fibres and is discharged by gravity.

GENERAL FEATURES OF ALL EMBODIMENTS

[00045] Thus, by the above-described methods, the maple syrup preferably has a sucrose content of at least about 63% by weight.

DESCBIPTION OF FIRST EMBODIlVIENT

[00046] The invention in this first embodiment provides a very gentle procedure for concentrating maple sap to form maple syrup. This involves a countercurrent or co-current flow of warm air, no hotter than about 25 degrees C, over a thin flowing stream of maple sap on a non-porous surface until usual maple syrup his provided. Usual maple syrup generally has a Brix of about 66degrees and a water activity of about 0.83-0.85. Of course, if the flow path is not sufficiently long to provide such maple syrup, the maple syrup may be used as the in coming flowing stream so that it becomes more concentrated.
[00047] In one preferred embodiment, the maple sap is atomized in an air circulating column and is moving downwardly by gravity through an upward flow of air in a counter-current fashion. The air which is fed into such air circulating is outside air, preferably is at ambient temperature.

[00048] In another preferred embodiment, the maple syrup has a Brix number of 61 +- 0.5 and/or up to about 40% of the water content is removed.

[00049] In another preferred embodiment, the maple sap, is evaporated until at least about 50% by weight of the water contained in maple sap is removed by atomization of the sap at a temperature up to about 25 deg. C in an air circulating column through which air is blown at low pressure and humid air is formed and is eliminated Preferably, the evaporation is conducted by circulating the maple sap in atomized form in counter-current through an airflow channel.

[00050] In another preferred embodiment, the maple syrup has a sucrose content of at least about 63% by weight.

DESCRII'TION OF SECOND EMBODIIVIENT

[000511 The ion exchange matrix may include one or more of the following:

a) an ion exchange resin having an ion which is identical with an ion of highly ionized solute;

b) a cation exchange resin having an acidic form, the cation exchange resin containing sulphonic acid groups or carboxylic acid groups;

c) an anion exchange resin having a basic form, the anion exchange resin containing quaternary ammonium groups or being in sulfate form;

d) an adsorbent comprising aluminosilicate or zeolite, e.g. a calcium-Y-type or calcium-X-type zeolite and containing one or more selected cations at exchangable cation sites, namely, sodium, barium or strontium ions or cationic pairs, namely barium and potassium or barium and strontium.

e) sulfonated polystyrene divinyl benzene crosslinked ion exchange resins exchanged with calcium ions or ammonium ions;

f) poly (4-vinylbenzeneboronic acid) resins g) sulfonated polystyrene cross-linked with divinyl benzene. isoprene, allyl methylacrylate, vinyl methacrylate, glycol methacrylate or glycol diacrylate. in alkali metal form, sodium being generally the preferred alkali metal.

h) a strong acid cation exchanger preferably in sodium or potassium form.
i) an anion exchange resins in a bisulfite, sulfite form or sulfateform;

j) an acrylic weakly acid cation exchange resin with a carboxylic functional group cross-linked with from about 1 to about 20%, preferably from about 3 to about 8% divinyl benzene, the resin being in hydrogen ion, potassium ion, sodium ion, magnesium ion or calcium ion forms, orother ion forms;

k) polystyrene matrix resins.

[00052] The procedure of concentration of maple sap may be carried out in a chromatographic column which is carried out at temperatures from about 10 to about 20.degree C.

[00053] As is usual in such chromatographic procedures, the component which is retained on the chromatographic resin, e.g., the maple sugars, must be eluted.
The eluent to be used in the chromatographic separation is not water. A preferred elutant is a partially-concentrated maple sap, e.g., as prepared according to the first embodiment of the present invention. Thus, the eluted product from chromatographic column is a partially-concentrated maple sap. The procedure may be repeated one or more times, each time the elutant being the immediately preceding eluted product from the chromatographic column, until a maple syrup of the desired Brix number is obtained.
[00054] The above-described procedure carried out in a chromatographic column for the concentration of maple sap may be carried out by a chromatographic simulated moving bed (SMB) method using the above-described resins with a small bead size. The average bead size should be in the range of about 300 to about 360 m. The resin of such sizes should preferably be used in a resin bed whose total resin bed length may be in the range of about 14 to 24 meters. Preferably the resin to be used should have a size in the range of about 220 to about 240 m.

[00055] The SMB method may be continuous or sequential or may comprise a combination of a continuous method and a sequential method.

[00056] The chromatographic bed in this SMB system for carrying out a SMB
method preferably includes a number of compartments. As used herein, a compartment refers to a section of the chromatographic bed which holds a column filling material bed and which comprises a forepart for disttibuting the maple sap to the middle part comprising the filling material bed and a rear part for collecting water component of the maple sap from this middle part.

[000571 As used herein, a feed compartment refers to a section of the chromatographic bed which receives the maple sap. In a sequential SMB
typically one compartment receives the feed maple sap. It is also possible to construct a sequential SMB so that feed maple sap enters into more than one compartment. In a continuous SMB all compartments typically receive the feed maple sap once during each cycle and therefore all compartments can also be feed compartments.

[00058] The procedure of concentration of maple sap may be carried out by a chromatographic simulated moving bed (SMB) process using resins with a small bead size. The average bead size should be in the range of 300 360 m. The resin of such sizes should preferably be used in a resin bed whose total resin bed length may be in the range of about 14 to 24 meters. Preferably the resin to be used should have a size in the range of 220 240 m.

DESCRIPTION OF THIItD EMBODIMENT

[00059] The third embodiment of the present invention comprises membrane distillation.

[00060] There are four types of membrane distillation, namely: direct contact membrane distillation (DCMD), where both the warm stream and the cooler stream are in direct contact with the membrane; air gap membrane distillation (AGMD), where the condenser surface is separated from the membrane by an air gap; sweeping gas membrane distillation, where the distillate is removed in vapour form by an inert gas; and vacuum membrane distillation, where the distillate is removed in vapour form by vacuum.

[00061] Membrane distillation differs from known distillation techniques, such as multi-stage flash, multiple effect distillation and vapour compression, in that a selective, porous membrane is used. This membrane forms a separation between a warm stream of maple sap and a cooler stream of maple syrup.

[00062] The selectively liquid porous membrane used in the third embodiment of the present invention can be any commercially-available membrane, which is made of materials, such as PTFE, PVDF, PP and PE and the like. Alternatively the membrane used in the third embodiment of the present invention can be any commercially-available or so-called asymmetric microfiltration membrane made of materials such as polyethersulphone, polysulphone, polyacrylonitrile, polyamides, etc.
Additional porous membranes which may be used include membranes of polyolefins (e.g.
polyethylene, polypropylene and the like), polysulfone, polyether sulfone, silicone resin, fluororesin and the like The porous membrane should have a porosity which is greater than about 70% and preferably greater than about 80% and a pore size which is larger than about 0.1 m to permit passage therethrough of water. It is preferred to change the surface characteristics of these membranes completely or partially by means of a coating or other surface modification.

[00063] Preferably the porous material selected is polypropylene, polyethylene or polytetraflorethene, having pore diameters of between 0.00001 and 0.005 mm, usually between 0.0001 and 0.0005 mm and a porosity greater than 70% and preferably greater than 80%.

[00064] The porous membrane may be formed by flat plate membranes or membrane sheets, optionally in a spirally wound configuration. The porous membrane may further be formed from hydrophilic material, such as threads or fabric.
Alternatively, the porous membrane may be hollow fibre membranes. The advantages of hollow fibre membranes for direct contact membrane distillation are known. As a result of the compact packing of membrane fibres, a relatively large surface area can be obtained. The porous membrane may consist of hollow fibres or capillary membranes placed in parallel. The concentrated maple sap flows through the lumen of these fibres.
[00065] A gap of predetermined thickness is provided between the condenser surface and the porous membrane. It is preferred that a gap thickness of 0.2 to 1.0 mm be provided in order to achieve a optimum separation. The thickness of the gap between the condenser surface and the porous membrane, can be provided by using a suitable spacer, preferably made of plastic. Such material should be highly porous (porosity preferably greater than 90%). The thickness of the material determines the thickness of the gap and should be less than 5 mm, preferably between 0.5 and 2 mm.

[00066] The gas gap may be at about atmospheric pressure, and may be filled with air or with hydrogen, helium, carbon dioxide, or nitrogen.

[00067] In addition to the use of an air gap, counter-current flow of a warm stream of maple sap feed and the concentrated stream of maple sap forms an important embodiment of the present invention.

[00068] The feed channels, through which the maple sap feed stream runs, may also preferably be formed by hollow fibres/capillaries, placed in parallel.
These channels are non-porous, that is to say are not water-permeable or are barely water-permeable. The discharge of the concentrated stream of maple sap, e.g., maple syrup, may take place via hydrophilic materials (such as a fabric) that has been applied to or around these fibres.
The maple syrup is preferably discharged by gravity.

CONCLUSION
[00069] The foregoing has constituted a description of specific embodiments showing how the invention may be applied and put into use. These embodiments are only exemplary. The invention in its broadest and more specific aspects is further described and defined in the claims which follow.

[00070] These claims, and the language used therein are to be understood in terms of the variants of the invention which have been described. They are not to be restricted to such variants, but are to be read as covering the full scope of the invention as is implicit within the invention and the disclosure that has been provided herein.

Claims (40)

What is claimed is:

1) A method for making maple syrup from a maple sap, said method comprising:
flowing a stream of maple sap along a supporting surface in countercurrent flow to an air stream whose maximum temperature is less than the boiling point until maple syrup having the desired Brix number is provided.

2) The method as claimed in claim 1, wherein said maple sap is atomized in an air circulating column and is moving downwardly by gravity through an upward flow of air in a counter-current fashion.

3) The method as claimed in claim 2, wherein said air which is fed into said air circulating is outside air.

4) The method as claimed in any one of claims 1 to 3, wherein said step is carried out first until a Brix number of 61 +/0..5 is obtained.

5) The method as claimed in any one of claims 1 to 4, wherein said step is carried out first until up to about 40% of the water content is removed.

6) The method as claimed in any one of claims 1 to 5, wherein the air blown into the air circulating column is at ambient temperature.

7) A method for making maple syrup from maple sap, comprising:
evaporating at least 50% by weight of the water contained in said sap by atomization of said sap at a temperature up to about 25 deg. C in an air circulating column through which air is blown at low pressure and humid air is formed and is eliminated

8) The method as claimed in claim 7, wherein said evaporation is conducted by circulating said sap in atomized form in counter-current through an airflow channel.

9) The method as claimed in any preceding claim, wherein said maple syrup has sucrose content of at least about 63% by weight.

10) A method for making maple syrup from a maple sap, said process comprising carrying out ion exchange chromatography in a chromatographic column containing a chromatography ion exchange resin, thereby to absorb maple syrup thereon and eluting maple syrup from said column by with a maple sap solution which is more concentrated than the original maple sap but is less concentrated than the maple syrup to be provided.

11) The method as claimed in claim 9, wherein said ion exchange resin is selected from the group consisting of : an ion exchange resin having an ion which is identical with an ion of highly ionized solute; a cation exchange resin having an acidic form, the cation exchange resin containing sulphonic acid groups or carboxylic acid groups; an anion exchange resin having a basic form, the anion exchange resin containing quaternary ammonium groups or being in sulfate form; an adsorbent comprising alumino silicate or zeolite, e.g. a calcium-Y-type or calcium-X-type zeolite ,and containing one or more selected cations at exchangable cation sites, namely, sodium, barium or strontium ions or cationic pairs, namely barium and potassium or barium and strontium;
sulfonated polystyrene divinyl benzene crosslinked ion exchange resins exchanged with calcium ions or ammonium ions; poly (4-vinylbenzeneboronic acid) resins; sulfonated polystyrene cross-linked with divinyl benzene. isoprene, allyl methylacrylate, vinyl methacrylate, glycol methacrylate or glycol diacrylate. in alkali metal form, sodium being generally the preferred alkali metal; a strong acid cation exchanger preferably in sodium or potassium form; an anion exchange resins in a bisulfite, sulfite form or sulfateform;
an acrylic weakly acid cation exchange resin with a carboxylic functional group cross-linked with from about 1 to about 20%, preferably from about 3 to about 8%
divinyl benzene, the resin being in hydrogen ion, potassium ion, sodium ion, magnesium ion or calcium ion forms, or other ion forms; and polystyrene matrix resins.

12). The method as claimed in any one of claims 9 to 11 carried out by a chromatographic simulated moving bed (SMB) method using resins with a small bead size.

13). The method as claimed in claims 12, which additionally comprises providing a plurality of zones within said chromatographic bed, each said zone comprising a section which holds said ion exchange resin and which comprises a forepart for distributing the maple sap to the middle part containing said resin and a rear part for collecting water component of the maple sap from this middle part.

14). The method as claimed in claim 12 or claim 13 including packing said resin is uniformly in said zones so that resin movement in said zones is effectively minimized.

15). The method as claimed in claim 13 including providing a total resin bed length in the range of about 14 to about 24 meters.

16). The method as claimed in any one of claims 9 to 15, wherein the bead size of the resin is from about 100 to about 200 µm.

17). The method as claimed in any one of claims 9 to 16, wherein the bead size of the resin is from about 125 to about 160 µm.

18). The method as claimed in any one of claims 9 to 17 wherein about 75% of the beads are within +/-20% range from the mean bead size.

19). The method as claimed in any one of claims 9 to 18, wherein the average bead size is in the range of about 300 to about 360 µm.

20). The method as claimed in claim 19, wherein the average bead size is in the range of about 220 to about 240 µm.

21). The method as claimed in any one of claims 9 to 20, wherein said resin bed has a total resin bed length may be in the range of about 14 to about 24 meters.

22). The method as claimed in any one of claims 11 to 20,wherin said method is continuous or sequential or comprise a combination of a continuous method and a sequential method.

23). The method as claimed in any one of claims 11 to 22 including providing a plurality of feed zones in a section of said chromatographic bed to receive the maple sap, wherein maple sap is fed into one zone or wherein maple sap is fed into more than one zone, or wherein maple sap is fed into all zones once during each cycle and therefore maple sap is fed into all zones.

24). The method as claimed in any one of claims 9 to 22, wherein said eluant comprises maple sap which is more concentrated that the feed maple sap.

25). The method as claimed in claim 24, wherein said eluant comprises maple sap which has passed at least once through said chromatographic column.

26). The method as claimed in any one of claims 9 to 22, which is carried out in a chromatographic column at temperatures from about 10 to about 20 degree C.

27). A method for making maple syrup from a maple sap, said method comprising carrying out a membrane distillation by contacting a moving stream of maple sap with a selectively liquid permeable membrane to permit the passage of water there through.

28). The method as claimed in claim 27 wherein said hydrophobic, porous, gas-permeable and liquid-impermeable membrane comprises any commercially-available membrane, which is made of PTFE, PVDF, PP or PE, or so-called asymmetric microfiltration membranes made of polyethersulphone, polysulphone, polyacrylonitrile, polyamides. polyolefins (e.g. polyethylene, polypropylene and the like), polysulfone, polyether sulfone, silicone resin or fluororesin.

29). The method as claimed in claim 27 or claim 28 wherein said porous hydrophobic membranes has a porosity greater than about 70% and preferably greater than about 80%
and pore size larger than about 0.1 µm, preferably between about 0.3 and 1.0 µm.

30). The method as claimed in any one of claims 27 to 29 wherein said porous hydrophobic membrane is polypropylene, polyethylene or polytetraflorethylene, having pore diameters of between 0.00001 and about 0.005 mm, preferably between about 0.0001 and about 0.0005 mm.

31). The method as claimed in any one of claims 27 to 30 wherein the surface characteristics of said porous membrane are changed completely or partially by means of a coating or other surface modification.

32). The method as claimed in any one of claims 27 to 31 wherein said porous membrane is a flat sheets or plate, optionally in a spirally wound configuration, or plate-like structures consisting of multiple capillary-like channels formed from threads or fabric.

33). The process as claimed in any one of claims 27 to 31, wherein said porous membrane comprises a hollow fibre membrane for direct contact membrane distillation to provide compact packing of membrane fibres , thereby providing a relatively large surface area.

34). The method as claimed in claim 33 wherein said hollow fibres or capillary membranes are placed in parallel.

35). The method as claimed in any one of claims 27 to 34, including providing a gap of predetermined thickness between the porous membrane and a condenser surface.

36). The method as claimed in any one of claims 27 to 34 wherein the thickness of said gap is defined by using a suitable spacer, preferably made of plastic which is highly porous preferably greater than about 90% and whose thickness determines the width of said gap, said gap being less than 5 mm, preferably between 0.5 and 2 mm. or 0.2 to 1.0 mm.

37). The method as claimed in any one of claims 27 to 36, including providing said gap is at about atmospheric pressure, or filling said gap with air, hydrogen, helium, carbon dioxide, or nitrogen.

38). The method as claimed in any one of claims 27 to 37 including providing a counter-current flow of a warm stream of maple sap feed and a concentrated stream of maple sap.

39). The method as claimed in any one of claims 27 to 38, including feeding maple sap through feed zones, said feed zones being delimited by hollow non-porous, non-water -permeable or barely water -permeable fibres/capillaries, placed in parallel.

40). The method as claimed in any one of claims 27 to 39, including discharging a concentrated stream of maple sap via a material (such as a fabric) that has been applied to or around said fibres and is discharged by gravity.