HK1175662A - Coffee treatment method - Google Patents

Description

Coffee processing method

The present invention relates to a process for producing concentrated mannooligosaccharides from coffee material, in particular from coffee extraction residue material. More specifically, the invention includes a process for treating hydrolyzed coffee extraction residue material to obtain mannooligosaccharides.

Background

Mannooligosaccharides are known to be used as food additives. Furthermore, mannooligosaccharides with a degree of polymerisation of 5 to 10 are known to have health benefits, such as lowering body fat, especially abdominal fat. By hydrolysis of mannan material, mannooligosaccharides can be produced as this breaks down mannan chains up to DP40 into useful shorter chains. Coffee is known to be a mannan-rich material.

There are many different techniques for hydrolyzing mannans. For example, U.S. patent No. 2,573,406 discloses a process for producing soluble coffee comprising hydrolyzing a portion of the coffee grounds in a suspension of about 1% sulfuric acid at 100 ℃ for about 1 hour, adjusting the pH of the hydrolysate, filtering the hydrolysate, and drying the extract. In another similar process described in U.S. patent No. 2,687,355, phosphoric acid is used instead of sulfuric acid. In another method disclosed in us patent 3,224,879, alkaline or acid hydrolysis is performed directly in the extraction sequence of coffee grounds that have been extracted at least at atmospheric pressure.

Thermal hydrolysis is also a well-known technique. However, when coffee is thermally hydrolyzed under conditions suitable for the production of MOS-rich products, undesirable impurities associated with the products are formed. In particular, extensive hydrolysis in percolators will produce tar and other impurities. These lead to an acidic and unpleasant character (note), or off-flavor, in the taste of the product. Thus, although MOS-rich products produced by thermal hydrolysis can be incorporated into products with strong flavour (e.g. coffee beverages), less strongly flavoured products are not suitable as additives.

It is known in the art to use activated carbon, adsorbent resins, ion exchange membranes, and combinations thereof to remove some impurities from MOS products, but these are time consuming and expensive to perform. Furthermore, they do not completely remove the undesirable off-note (off-note) produced by thermal hydrolysis.

Accordingly, it is desirable to provide a method of providing MOS-enriched additives for food and beverages that addresses at least some of the disadvantages associated with the prior art or provides a useful alternative way to do so.

Summary of The Invention

According to a first aspect, the present disclosure provides a method for obtaining a Mannooligosaccharide (MOS) -rich precipitate from coffee, the method comprising the steps of:

(i) providing a MOS-containing hydrolysate derived from coffee extraction residue material;

(ii) contacting the MOS-containing hydrolysate with an organic solvent to form a suspension; and

(iii) and recovering the precipitate.

In a second aspect, the present disclosure provides a product comprising a precipitate obtainable by the process of the present disclosure. The product is preferably a food or beverage.

In a third aspect, the present disclosure provides the use of the process described herein to reduce and preferably remove off-flavours from coffee extracted residual material used as an additive in beverages or foodstuffs. More specifically, the present disclosure provides for the use of the methods described herein to provide a flavorless precipitate as an additive in a beverage or food product.

In a fourth aspect, the present disclosure provides the use of a precipitate obtainable by the method of the present disclosure for the manufacture of a medicament for reducing body fat levels.

The disclosure will now be further described. Various aspects of the disclosure are defined in more detail in the following sections. Each aspect so defined may be combined with any other aspect or aspects unless clearly indicated to the contrary. In particular, any feature described as preferred or advantageous may be combined with any other feature described as preferred or advantageous.

As used herein, "mannan" broadly refers to any polysaccharide composed of d-mannose units. The monosaccharide d-mannose is an isomer of aldohexose and d-glucose, differing only in that the hydroxyl groups closest to the carbonyl group have the opposite spatial arrangement. Mannans found in coffee extraction residue material can have up to 40 d-mannose units in the polysaccharide chain and are typically linked by β 1-4 glycosidic linkages, which are the same as those found in cellulosic polymers. Since coffee mannan is essentially a linear polymer with a cellulose-like bonding force, it is also a difficult polymer to hydrolyze. However, under certain reaction conditions, the mannan fraction can hydrolyze without affecting the remaining cellulose fraction.

"degree of polymerization" or "DP" refers to the number of monosaccharide units that make up a given mannooligosaccharide. Thus, a mannooligosaccharide such as DP4 consists of 4 mannose units.

"mannooligosaccharides" or abbreviated MOS is intended to include mannose and mannose up to mannodecaose (DP 10). Mannooligosaccharides with a DP of 1 are technically monosaccharides but are called oligosaccharides, since the mixture of oligosaccharides may comprise some monosaccharide units. Mannooligosaccharides generally comprise a plurality of oligosaccharides with different degrees of polymerization.

MOS can be produced by hydrolysis of mannan. Sources of mannan include raw coffee beans, roasted coffee beans, spent coffee grounds. Any type of coffee beans from any source may be utilized. Examples of coffee that may be used include Arabica (Arabica), Robusta (Robusta), liberia (Liveria), and the like. A single type of coffee or a blend of different types of coffee may be utilized. Coffee beans having inferior quality or size, including those having little or no commercial value, may also be used. The "coffee extraction residue material" for producing MOS-containing material is intended to mean roasted and ground coffee material that has been at least partially extracted. Coffee extraction residue material is commonly obtained from industrial coffee percolation systems. Coffee that has been partially thermally hydrolyzed to hydrolyze less stable polysaccharides (e.g., arabinogalactans) is particularly useful as coffee extraction residue material. The waste residue from an industrial percolation system is an example of coffee that has been subjected to atmospheric extraction and partial thermal hydrolysis, so that about 35-60% of the initial roasted coffee grounds are extracted, typically about 50%. For the sake of simplicity, "coffee extraction residue material" is also referred to herein as "coffee material".

"hydrolysate" is the product of the hydrolysis step. In this way, the mannan-containing coffee material is processed to produce MOS from the mannan fraction. That is, the hydrolysis process is used to hydrolyze mannans which may have a DP of 10 to 40 or higher in the coffee material to form oligosaccharides having a DP of 1 to 10. Hydrolysis of mannan materials can be carried out using hydrolysis methods, which can include acid hydrolysis, thermal hydrolysis, enzymatic hydrolysis, microbial fermentation hydrolysis, and mixtures thereof. Thermal hydrolysis is particularly preferred due to the simplicity of the processing steps required and the speed of processing. Furthermore, unlike acid hydrolysis, no further steps, such as neutralization, are required.

Enzymatic hydrolysis can be carried out by suspending the mannan material in an aqueous medium and adding suitable commercially available enzymes, e.g., cellulases and hemicellulases. Enzymatic hydrolysis may be performed using standard conditions known to those of ordinary skill in the art.

Microbial fermentation can also be used to hydrolyze mannan materials. The mannan material can be fermented using a microorganism that produces an enzyme capable of hydrolyzing mannan. Microorganisms producing enzymes such as cellulase and hemicellulase can be used. An example of a suitable microorganism is Basidiomycota (Basidiomycota).

The present disclosure produces a precipitate rich in Mannooligosaccharides (MOS) from coffee. By "MOS-rich" is meant that the precipitate is predominantly MOS. I.e. more than 50%, more preferably more than 75%, most preferably more than 90%. Ideally, the precipitates are substantially all MOS. I.e. more than 95%, more preferably more than 98%, most preferably all MOS, except for unavoidable impurities. All percentages are by weight of the dry components in the mixture.

The method of the present disclosure includes at least three steps. These are:

(i) providing a MOS-containing hydrolysate derived from coffee extraction residue material;

(ii) contacting the MOS-containing hydrolysate with an organic solvent to form a suspension; and

(iii) and recovering the precipitate.

It will be appreciated that although these steps need to be performed in sequential order, they may form part of a continuous process in which any step may occur simultaneously or overlap to some extent. The process can be carried out continuously or batchwise.

The present inventors have found that by using solvent extraction techniques, off-flavours can be surprisingly removed from hydrolysates (particularly thermal hydrolysates). Furthermore, this has the dual benefit of providing improved flavour as well as leading to a more desirable concentration of DP5-DP10 MOS.

The term "organic solvent" as used herein includes any carbon-containing solvent. Preferably, the solvent is substantially polar, i.e., has a dielectric constant of at least 15 at 25 ℃. Preferably, the solvent is approved and safe for human consumption. Most preferably, the solvent is an alcohol. The alcohol is preferably C₁-C₆Alcohols, for example, methanol, ethanol, n-propanol, isopropanol, or combinations of two or more thereof. Other solvents that may be used include acetone and acetonitrile. Ethanol is the most preferred solvent.

The solvent is preferably added in excess to ensure that most of the MOS is recovered. The proportion added may be measured as% v/v of solvent added to the hydrolysate in liquid form. Preferably at least 50% v/v, more preferably at least 70%, most preferably at least 90% solvent is added. FIG. 2 shows an example of how the recovery rate varies according to the proportion of ethanol added. To ensure high process yields, it is preferred to use not more than 99% v/v solvent.

The MOS-containing hydrolysate derived from the coffee material is preferably at least partially dissolved in water prior to contacting with the organic solvent. Preferably, the hydrolysate is completely dissolved to form a mixture and when mixed with an organic solvent, a precipitate is finally formed. This prevents undesirable solid impurities from mixing with the precipitate, although these impurities may be pre-precipitated out or removed by any conventional technique.

Step (iii) of recovering the precipitate may be carried out using any conventional technique for separating solids from liquids. For example, by evaporation, decantation or filtration, and optionally a centrifugation step, and any combination of two or more of the foregoing. Preferably the technique involves lowering the temperature of the suspension as this increases the rate of precipitate formation and increases the fraction of MOS that precipitates out. The lowering of the temperature may be the result of natural cooling, in particular if the MOS-containing hydrolysate from the thermal hydrolysis step is still warm. Alternatively, the mixture may be initially warmed to allow cooling. Cooling may be active in order to increase processing speed and reduce the time it takes to produce the product. Active cooling techniques are well known in the art.

The inventors have found that the process of the invention advantageously increases the ratio of DP5-DP10MOS to DP1-DP10 MOS in the precipitate relative to the ratio of DP5-DP10MOS to DP1-DP10 MOS in the MOS-containing hydrolysate. Preferably at least 50%, more preferably at least 100%, most preferably at least 200%. Without wishing to be bound by theory, this may be due to the fact that shorter chain mannooligosaccharides, which are more soluble in water than longer chain oligosaccharides, remain in any water fraction present in the suspension. Since they remain dissolved in this way, they do not form part of the remaining precipitate.

The precipitate obtained in the process of the present disclosure may still be wet or moist after recovery from the suspension. Thus, a further drying step may be included. Drying steps are well known in the art and any suitable drying step may be performed. Particularly suitable processes are carried out under reduced pressure. Drying methods include, but are not limited to, spray drying and freeze drying.

Further purification steps involving activated carbon, adsorbent resins, ion exchange membranes and combinations thereof may be used. Desalting and deacidifying may be performed using ion exchange resins and/or ion exchange membranes. Combinations of these methods may also be used. Further purification can be performed at higher dosage levels or when the hydrolysate is to be used in certain types of food or beverage.

The soluble solids obtained as a precipitate according to the process of the invention can be used as food or beverage additive, for example in coffee. Furthermore, in view of the reported health benefits of DP5-DP10MOS, the precipitate may be included in these products as a health-promoting additive. In particular, the precipitate obtainable by the method of the present disclosure may be used for the manufacture of a medicament for reducing body fat levels. The medicament may be in the form of a food or beverage. Suitable food products include dairy products, bakery products and ready-to-eat meals, as well as ready-prepared beverages or compositions for preparing convenient beverages. Preferably the food or beverage is not a coffee flavoured food or beverage.

Preferably the MOS containing hydrolysate is prepared in a process of hydrolysing a coffee material, e.g. partially extracted roast and ground coffee in a thermal hydrolysis step. This can be done in a reactor by a high temperature short time process, preferably without introducing any added acid catalyst. If an acid catalyst is added, this complicates the process and the product may require further neutralization. Tubular plug flow reactors are convenient, but any reactor that provides relatively high temperature, short time reactions is sufficient. The time/temperature relationship is selected to cause solubilization followed by hydrolysis of the native mannan oligomers from about the DP 10-DP 40 range to about the DP1-DP10 range.

In the reactor, the coffee material is subjected to a temperature of about 150 ℃ to 300 ℃, preferably 200 ℃ to about 260 ℃, for a time period of about 1 minute to about 15 minutes to partially hydrolyze the mannan to a range of about DP1 to DP 10. After hydrolysis, the soluble MOS-containing hydrolysate can remove any solid impurities remaining from the coffee material.

Preferably the coffee material is at least partially hydrated in a liquid, typically water, before being fed to the reactor, preferably a plug flow reactor. This makes it easier to handle the material as a result of the formation of the slurry. The hydrated coffee material should be homogeneous, i.e., should be uniformly distributed throughout. If made in batches beforehand, steps should be taken to ensure homogeneity, for example recirculation by means of slurry pumps. If the hydrolysis reaction takes place in a plug flow reactor, preferably a slurry is used which should be 5-25 wt%, most preferably 10-20 wt% of dry basis coffee material. When a plug flow reactor is utilized, if the concentration of the slurry exceeds 25 wt%, the slurry becomes too thick to ensure proper flow. When using different reactors, such as extruders, it is generally not necessary to prepare a slurry. For example, waste residue from a conventional diafiltration system, which typically contains about 65 wt% to 80 wt% liquid, may be fed directly to such an extruder without further dilution. Slag containing about 40 wt% to 65 wt% liquid may also be used. This slag may be partially dewatered, such as by screw pressing, air drying, or other methods known in the art.

Suitable continuous reactors include those that promote relatively high temperature, short time reactions, such as single or twin screw extruders or plug flow tubular reactors. Suitable batch reactors are so-called pressure containment vessels, such as autoclaves, or explosion blowers, in which the coffee extraction residue material is placed in the reactor vessel and subsequently pressurized and heated together with steam. Causing a sudden and explosive release of pressure and discharge of the contents from the reactor vessel. The soluble solids are then leached with water from the material thus discharged from the reactor vessel. Plug flow tubular reactors are particularly convenient. A plug flow tubular reactor is essentially a cylindrical section of pipe in which reactions can occur. An orifice or other suitable means is placed on the discharge end of the reactor to control the pressure in the reactor and the rate of discharge from the reactor. "plug flow" refers to the velocity profile of the slurry flowing through the reactor. Typically, the fluid exhibits a parabolic distribution velocity, wherein the velocity of the fluid in the middle of the conduit is higher than the velocity of the fluid flowing near the wall. In an ideal plug flow reactor, the velocity profile is flat due to the geometry of the vessel and the nature of the flow, thus ensuring the same high temperature, short time reaction conditions for all materials in the reactor by minimizing the variation in residence time.

The elevated temperature is achieved in the reactor in any of several ways. For example, the slurry may be passed through a heat exchanger that is part of the reactor chamber, or separate from the reactor chamber. The temperature can then be maintained by simply adiabatic insulation of the reactor. Alternatively, high pressure steam may be injected directly into the reactor as a means of raising the temperature. Although steam may have some dilution of the slurry, this heating is extremely fast, allowing for short reaction times. The selection of the preferred heating method and the determination of the diameter size of the reactor and the orifice are within the skill of one in the art based on standard design principles.

The time/temperature conditions maintained in the reactor are of course critical to ensure that mannan hydrolysis occurs. Excessive temperatures and pressures are known to increase undesirable tar and off-flavors. However, the treatment methods of the present disclosure make these easier to remove. This means that higher temperatures and pressures than conventionally employed can be used.

It has been found that the reaction temperature should be from about 150 ℃ to 300 ℃, preferably from about 200 ℃ to about 260 ℃, most preferably from about 210 ℃ to 240 ℃, in order to solubilize and hydrolyze the mannan portion to the desired range. At least 50% of the mannan fraction is removed from the coffee residue, preferably 75%, more preferably 90%. This temperature is preferably combined with the pressure in the reactor, which is between atmospheric pressure and 100 atmospheres, more preferably between about 20 atmospheres and about 40 atmospheres. This helps to increase the yield.

The desired reaction time is found to be from about 1 minute to about 15 minutes, preferably from about 2 to about 8 minutes, to effect the hydrolysis.

At any given temperature within the temperature range of the present method, mannan will be solubilized and hydrolyzed. The yield will increase with residence time up to a maximum, and subsequently the yield will decrease, as the oligomers degrade to form volatiles or insolubles, i.e. tar or sludge. The kinetics of the reaction of the present invention will generally double for every 10 ℃ increase in temperature. At higher temperature ranges, the residence time must fall at the lower end of the specified time range; vice versa, at lower temperature ranges, the residence time must fall at the higher end of the time range.

The slurry is preferably passed out of the furnace quickly to reduce the pressure experienced by the slurry to substantially atmospheric pressure. This rapid reduction in pressure causes the slurry to expand and evaporatively cool, thereby "quenching" or immediately terminating the hydrolysis and browning reactions. By quenching the reaction in this way, the hydrolysis reaction time can be controlled within a prescribed period of 1 to 15 minutes, and the reaction has high reliability.

The separation can be performed by any method of solid-liquid separation known in the art. For example, the slurry may be filtered to remove hydrolyzed partially extracted roast and ground coffee therefrom. Alternatively, the slurry may be separated by centrifuging the slurry, such as in a basket centrifuge. MOS-containing hydrolysates used in the present disclosure are preferably formed from soluble elements of the slurry, as these soluble elements contain most mannooligosaccharides.

The disclosure is further illustrated in the following examples and with reference to the following figures:

fig. 1 is a flow chart showing steps that may be performed in the method of the present disclosure.

Figure 2 shows how the weight percentage of mannose recovered from a hydrolysate derived from coffee material (% by initial content) varies according to the amount of ethanol added (% v/v).

Figure 3 shows the relative DP fraction (in g/100 g) present in the unprocessed hydrolysate (light grey) compared to the precipitate (in g/100 g) formed by the method of the present disclosure in 80% v/v ethanol (black).

Examples

A quantity of coffee extraction residue material was mixed with water to form a slurry (10 wt% solids) and passed into a plug flow reactor. The slurry was heated to 230 ℃ for 6 minutes. After this thermal hydrolysis step, solids are extracted (by centrifugation) from the slurry and discarded, leaving a liquid hydrolysate 1 (see flow chart in fig. 1).

The liquid hydrolysate 1 is then mixed with sufficient ethanol (food grade) in a mixing step 3 to form an 80% v/v ethanol solution 5. The mixing step 3 is carried out on a continuous flow of liquid hydrolysate 1 passing through the plug flow reactor.

The ethanol solution 5 was allowed to cool to cause the MOS portion to precipitate out. After precipitation, the suspension is centrifuged in a separation step 7. The separation step 7 results in a supernatant 9 and a precipitate 11, the supernatant 9 being discarded.

The precipitate 11 is then redissolved in a minimum amount of water and freeze-dried in a final step 13. This results in a deodorized MOS-rich extract 15. Extract 15 was found to be substantially odorless.

Extract 15 and hydrolysate 1 were analyzed using the following analytical methods:

■ carbohydrate analysis: after hydrolysis with sulfuric acid and amperometric detection, this was carried out using an anion exchange system.

■ Degree of Polymerization (DP) analysis: capillary electrophoresis system using a coupled Diode Array Detector (DAD).

The mannose recovery results for the hydrolysate precipitates at different ethanol addition levels are shown in figure 2. It can be seen that recovery increases as the ethanol content increases.

In fig. 3, the DP profiles of both hydrolysate 1 and precipitate extract 15 are shown. For the precipitate extract 15, most of the mannose recovered was DP 5-8 (see Table 1 below). The DP 5-8 concentration in the precipitate extract 15 was about 200% of the hydrolysate 1. The precipitate extract 15 is free of initial off-flavors that are removed during the process.

TABLE 1

Sum of DP5-DP8, hydrolyzate	36.35
		Sum of DP5-DP8, hydrolysate precipitate	74.96
Percentage increase (hydrolysate/precipitate)	206％

The values-DP 5-DP8 are expressed in percentages.

The precipitate recovered in the previous examples was then introduced into a coffee beverage product and subjected to consumer testing. The purpose of the test was to demonstrate that ethanol precipitation can significantly reduce the acidity and bitterness perception of coffee.

Under red light in a white paper cup (to limit appearance bias), 2 cups of coffee were presented to the evaluator simultaneously. The taster tasted each cup in a separate booth and circled the most sour cup followed by the most bitter cup (the sample can be tasted again). 35 semi-trainers (semi-trained) participated.

Compared to a conventional cup of coffee, 31 tasters chose the cup of coffee containing the precipitate of the present disclosure to be less sour, and 28 tasters found it to be less bitter. The samples obtained by ethanol precipitation can therefore be considered significantly less acidic and less bitter with a 95% confidence.

The foregoing detailed description is provided by way of illustration and description, and is not intended to limit the scope of the appended claims. Many variations in the preferred embodiments of the invention described herein will be apparent to one of ordinary skill in the art and remain within the scope of the appended claims and their equivalents.

Claims (17)

1. A method for obtaining a precipitate enriched in Mannooligosaccharides (MOS) from coffee, said method comprising the steps of:

(i) providing a MOS-containing hydrolysate derived from coffee extraction residue material;

(ii) contacting the MOS-containing hydrolysate with an organic solvent to form a suspension; and

(iii) and recovering the precipitate.

2. The process of claim 1 wherein the organic solvent is C₁-C₆An alcohol.

3. The process of claim 1 or claim 2, wherein the organic solvent is methanol, ethanol, n-propanol, isopropanol, or a combination of two or more thereof.

4. The process of any one of the preceding claims, wherein prior to step (ii), the MOS-containing hydrolysate derived from coffee material is at least partially dissolved in water.

5. The method of any one of the preceding claims, wherein step (iii) comprises reducing the temperature of the suspension and separating the precipitate from the suspension.

6. The process of claim 5, wherein the separation of the precipitate from the suspension is performed by evaporation, decantation or filtration, and optionally comprises an initial centrifugation step.

7. The process of any of the preceding claims, wherein the ratio of DP5-DP10MOS to DP1-DP10 MOS in the precipitate is at least 50% greater than the ratio of DP5-DP10MOS to DP1-DP10 MOS in the MOS-containing hydrolysate.

8. The method of any one of the preceding claims, wherein the MOS-containing hydrolysate is prepared by:

(a) providing a coffee extraction residue material; and

(b) thermally hydrolyzing the coffee material to form a MOS-containing hydrolysate.

9. The method of claim 8, wherein the step of thermally hydrolyzing the coffee material is performed under one or more of the following conditions:

(1) a temperature of 150 ℃ to 300 ℃;

(2) no acid catalyst is added; and/or

(3) From atmospheric pressure to 100 atm.

10. The process of claim 9, wherein the reaction is carried out under the following conditions:

(i) a temperature of 200 ℃ to 260 ℃; and/or

(ii) A pressure of 20-40 atmospheres.

11. The method of any one of the preceding claims, wherein the method further comprises the steps of:

(iv) drying the precipitate.

12. The method of claim 11, wherein the drying step is performed under reduced pressure.

13. The method of any one of the preceding claims, wherein the method further comprises the step of including the precipitate as an additive in a beverage or foodstuff.

14. A product comprising a precipitate obtainable by the process of any one of claims 1 to 13.

15. Use of the process of any one of claims 1 to 13 for the extraction of residual material from coffee to reduce off-flavours, as an additive in beverages or foodstuffs.

16. Use according to claim 15 for providing a tasteless precipitate for use as an additive in beverages or food products.

17. Use of a precipitate obtainable by the method of any one of claims 1 to 13 in the manufacture of a medicament for reducing body fat levels.