Maturation container for spirits and method of constructing same

Abstract

A maturation container and method of maturing spirits that incorporates a polymeric material (10) into a wall of the container. The material (10) is preferably Polylactic Acid (PLA) which has known oxygen permeation properties suited to maturation but is substantially impermeable to ethanol. Use of such a material is proposed to supplement or replace traditional wooden barrel methods of storage.

Claims

1. A maturation container for spirits, the maturation container including a wall incorporating polylactic acid (PLA) wherein the wall of the container must have a property of being oxygen permeable while preventing loss of the spirit.

2. The container of claim 1 wherein PLA is incorporated as a layer within a laminate wall or as a plastic blend thereof.

3. The container of claim 1 wherein wood fragments, charred wood fragments and/or dust are incorporated within the container or upon/within the wall thereof.

4. The container of claim 1 wherein PLA material forms a flexible wall supported by a rigid superstructure.

5. The container of claim 1 wherein PLA is formed in a layer incorporated with a wooden cask wall.

6. The container of claim 1 wherein the oxygen transmission rate of the wall is above 650 cc−mil/m.sup.2−day−atm.

7. The container of claim 1 wherein water permeability of the wall is in the range of 0.083 mg/cm.sup.2 to 0.64 mg/cm.sup.2 of barrel contact surface per day.

8. The container of claim 1 wherein ethanol permeability of the wall is below 0.32 mg/cm.sup.2 per day.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) FIG. 1 illustrates a schematic view of a maturation vessel wall material according to the invention indicating various permeability properties; and

(2) FIG. 2 shows a comparison of water loss in a control and vodka sample.

DETAILED DESCRIPTION OF THE INVENTION

(3) FIG. 1 shows a layer of polymer material that may substantially form or be incorporated into the wall of a container for maturing spirits. The particular example of material 10 is an injection stretch blow-moulded PLA material. Other injection moulded alternatives are possible, e.g. to achieve thicker walls with less crystallinity. The left side of the material, denoted “A” represents the outside atmosphere of a storage space where the container would be located, e.g. 78% nitrogen, 21% oxygen and 1% other atmospheric gases. The right side of the material 10 is generally denoted “S” which is the spirit resident within the container.

(4) The spirit S may be any known alcoholic beverage variant, such as rum or tequila. The invention may be capable of being utilised with any spirit industry, although regulations and tradition may dictate that a container must be substantially built from a particular material, e.g. wood. Nevertheless, the invention may be incorporated into a more conventional vessel such as a wooden barrel as a layer or, indeed, the polymer itself could have wood fragments impregnated therein in order to impart particular flavour characteristics. Conventional bottles made from PLA are typically injection stretch blow molded (ISBM); in the case of a larger scale maturation application it is expected that containers could be made using IBM (injection blow molding), EBM (extrusion blow molding), rotational molding, or other methods like thermoforming.

(5) An arrow denoted O.sub.2 shows a certain permeability to oxygen passing through the barrier 10. Oxygen permeability characteristics for a PLA wall material are known and/or can be determined by experiment and tabulated. These characteristics can be tailored (by controlling thickness and/or formulation) to provide an oxygen permeable barrier that is suitable for maturation of a particular spirit S.

(6) In the case of PLA being used as the barrier material 10 it is also expected that water, denoted by an arrow H.sub.2O, would pass through wall 10 and evaporate into the atmosphere. Water loss is not a significant problem since this can be easily addressed by suitable supplementation during the bottling process in order to adjust for required ABV. Alternative formulations may improve, i.e. reduce, water loss denoted by arrow 11. By contrast, if desirable, it may be possible to increase water loss, without corresponding loss of alcohol, as a means of concentrating the product.

(7) According to the invention, it is necessary to substantially prevent loss of ethanol, which is denoted by arrow E in FIG. 1. PLA is now known, unexpectedly, to provide such a barrier, while allowing oxygen and a proportion of water to pass therethrough.

(8) Table 1 below shows the results of water loss for a prior art PLA water bottle at ambient temperature with the following specifications:

(9) Weight=25 g

(10) Height=18 cm

(11) Diameter=6.5 cm

(12) Average wall thickness=0.46 mm

(13) Surface area below neck (estimated)=427 cm.sup.2

(14) TABLE-US-00001 TABLE 1 Total Loss, Water Running Days Water (g) Water (g) Avg Daily Loss (g) 0 530.2 0.0 0 7 528.6 1.6 0.23 14 526.8 3.4 0.24 21 525.0 5.2 0.25 28 523.2 7.0 0.25 35 521.5 8.7 0.25 42 519.6 10.6 0.25 50 517.4 12.8 0.26 56 515.9 14.3 0.26 63 514.1 16.1 0.26

(15) FIG. 2 shows a comparison of water loss over time for a control water content and a 40% ABV vodka. It will be apparent that both containers show a consistent fluid loss as time passes. However, in the case of the vodka it was found that all fluid loss could be attributed to water because the ABV increased over time. For example, the initial ABV was measured at 39.7% and, after thirty days, was 41.5%. Both tests were conducted under accelerated conditions at 40° C. whereas the results in Table 1 come from an experiment conducted at ambient temperature over 60 days. In both cases the closures were foil lined in order to be impermeable.

(16) Experiments have shown that PLA has a comparable oxygen transmission rate compared to wooden barrels. For example, wine matured in French oak barrels will receive 15-45 mg O.sub.2/L per year (source: “Oak Stave Oxygen Permeation: A New Tool to Make Barrels with Different Wine Oxygenation Potentials”, Journal of Agricultural and Food Chemistry, January 2015) whereas PLA has an oxygen transmission rate (OTR) of approximately 19.2 mL of O.sub.2/L per month. This corresponds to 329 mg O.sub.2/L per year but, of course, is dependent on thickness and other attributes such as crystallinity and orientation. It is broadly desirable that the OTR would be greater than about 250 mg O.sub.2/L per year for maturation purposes. In terms of oxygen transmission that takes into account material thickness, the reported permeation rate for the PLA used according to the examples herein is 675 cc−mil/m.sup.2−day−atm. This material gives satisfactory results and so the desirable range of oxygen transmission is likely in the range 650 to 750 cc−mil/m.sup.2−day−atm. For comparison HDPE is reportedly 3100 cc−mil/m.sup.2−day−atm.

(17) Also for contrast, an average OTR for a 500 mL PET container is approximately 0.040 mL O.sub.2/package per day or 0.11 PPM of O.sub.2/package per day. PLA is approximately 9 times more permeable to oxygen than PET, i.e. 0.32 mL (0.91 ppm) O.sub.2/package per day for a 500 mL bottle.

(18) For reference, prior art document WO03/022983 describes a rate of oxygen being dissolved into wine, through a polymer tube, in the range of 1-100 mL/L of wine per month.

(19) Table 2 below provides comparative sensory results for rum in three maturation containers, i.e. a glass blind control, PLA (invention) and PET. The liquid was 75% ABV and 1.5 grams American oak large heavy toast wood chips were deposited in each container. Storage was 3 months at 40° C.

(20) TABLE-US-00002 TABLE 2 Mean DFC Sample Score Panelist 1 Panelist 2 Panelist 3 Panelist 4 Panelist 5 Panelist 6 Blind Control - 9.3 10 9 8 10 9 10 Glass PLA 6.0 6 6 6 5 7 6 PET 9.7 9 10 10 9 10 10

(21) The PLA container is notably distinguished from the control and PET containers. In general, based on panellist comments (not shown), the taste is considered improved, concluding that the liquid has changed (matured) in a PLA container while no significant change was observed in the PET or glass. In the context of the experiment a low score is desirable as this shows a variation from the glass control.

(22) Table 3 below provides comparative sensory results for tequila distillate in three maturation containers, i.e. a glass blind control, PLA (invention) and PET. The liquid was 55% ABV and 1.5 grams American oak large heavy toast wood chips were deposited in each container. Storage was 3 months at 40° C.

(23) TABLE-US-00003 TABLE 3 Mean DFC Sample Score Panelist 1 Panelist 2 Panelist 3 Panelist 4 Panelist 5 Panelist 6 Blind Control - 10.0 10 10 10 10 10 10 Amber Glass PLA 5.5 5 6 3 7 6 6 PET 8.3 8 8 8 8 10 8

(24) Again, the PLA container is notably distinguished from the control and PET containers. The liquid has changed (matured) in a PLA container while less change was observed in the PET or glass.

(25) The PLA containers of the rum and tequila experiments respectively also exhibited an increase in ABV over the three month test period. Since water, but not alcohol, permeates through the PLA wall there was a predictable and measurable ABV increase of 76 to 80% for rum and 54 to 58% for tequila. This simply illustrates that there is an ABV gain across multiple spirit types.

(26) Polymer formulation is a well-established field and it is expected that the PLA properties can be adapted into a suitable container for larger scale spirit maturation for pilot plant and/or full production purposes. PLA could be incorporated as a blended polymer wall, a layer within a laminate, and/or as part of a more conventional cask design. Furthermore, it is foreseen that desirable properties (taste profile etc.) from traditional methods, e.g. wooden barrels, could be incorporated into a polymer layer, such as by impregnating wood dust or generally inserting fragments into the bottle or container. Charred oak/compound oak could be incorporated into a PLA sheet or otherwise moulded/formed into a bag for a bag-in-box application.

(27) Once aware of the nature of invention, conventional experimental and manufacturing techniques can be used to optimise and implement the invention as outlined in the appended claims.