WO2013106071A1

WO2013106071A1 - Treatment of wooden equipment used in the food and beverage processing industry

Info

Publication number: WO2013106071A1
Application number: PCT/US2012/038487
Authority: WO
Inventors: Bryan Richard Tudhope
Original assignee: Bryan Richard Tudhope
Priority date: 2011-06-17
Filing date: 2012-05-18
Publication date: 2013-07-18

Abstract

A method is provided for treating wooden equipment used in the food and beverage processing industry in order to kill microbiological species in the wood, thereby avoiding spoilage of the contents. The method comprises contacting at least one surface of the wooden equipment, typically a barrel, with a heating fluid in order to elevate the temperature of said surface to between 60 degrees C (140 degrees F) and 74 degrees C (165 degrees F), most preferably about 71 degrees C (160 degrees F). The elevated temperature is maintained until such time as the temperature through the thickness of the wooden equipment has risen to a minimum temperature of 60 degrees C (140 degrees F), and preferably about 63 degrees C (145 degrees F). In the instance of a barrel, heating may be effected from either the inside or the outside, or both.

Description

TREATMENT OF WOODEN EQUIPMENT USED IN THE FOOD AND BEVERAGE PROCESSING INDUSTRY

FIELD OF THE INVENTION

This invention relates to the treatment of wooden equipment used in the food and beverage processing industry, especially, although not exclusively, containers, in order to partially sterilize same and allow the equipment to be reused with a substantially reduced risk of contamination by particular microbes. In particular, but not exclusively, the invention relates to the treatment of wooden barrels used in the wine production industry.

BACKGROUND TO THE INVENTION

Dekkera/Brettanomyces yeasts are well known for their involvement in the production of phenolic compounds within wine that cause aroma defects. Such defects are usually described as "horse sweat", "barn yard" or "bandaid" aromas. Brettanomyces yeast and its ascosporogenous sexual form within Dekkera are reported to transform hydoxycinnamic acids, p- coumaric and ferulic acids into volatile phenols (Heresztyn, 1986, Chatonnet et al., 1995; Edlin et al., 1995).

The production of volatile phenols may occur at different stages of the winemaking process. However, Dekkera/Brettanomyces is often associated with spoilage of barrel-aged wines due to insufficient wood sanitation (Chatonnet et al., 1993). The taint resulting from these spoilage organisms can lead to financial losses within the wine industry. It is well known that these organisms can thrive within the pores of wooden barrels and can effectively contaminate wine or any other spoilage prone fluid that is stored in the barrels for aging purposes. The preferred method of controlling microorganisms within wine barrels, as far as applicant is aware, is by injecting steam into the barrel for a preset length of time. Unfortunately, due to the heat insulating characteristics of wood, the heat introduced by way of the steam does not penetrate to the necessary depth of about 7mm into the wood in order to effectively kill the spoilage organisms. The existing procedure is therefore not sufficiently effective. A longer period of exposure to steam is not desired as it can leave "burnt" flavors from residual wine present in the pores of the wood of the wine barrels.

The thermal death point of D. bruxellensis and D. anomala was discussed by J.A. Couto, F. Neves and F. Campos and T. Hogg in a paper entitled "Thermal inactivation of the wine spoilage yeasts Dekkera/Brettanomyces" wherein, in tests run on wine, a 6D reduction (99.9%) of yeast population was achieved at 44.5°C (1 12.1 °F) within a time span of 0.04 minutes.

Whilst it is possible to treat the wine in the manner envisaged in that paper, it is preferable to avoid the production of wine spoilage yeasts Dekkera/Brettanomyces insofar as it is possible and with this end in view there is a need for a more effective treatment of wooden equipment, especially wooden wine barrels used in a wine production process preparatory to contact with a batch of wine.

SUMMARY OF THE INVENTION

In accordance with this invention there is provided a method for the treatment of wooden equipment used in the food and beverage processing industry in order to kill microbiological species that may be present in the wood, the method comprising the steps of contacting at least one surface of the wooden equipment with a heating fluid in order to raise the temperature of said surface to an elevated temperature of between 60°C (140°F) and 74°C (165°F) and maintaining said surface at said elevated temperature until such time as the temperature through the thickness of the wooden equipment has risen to a minimum temperature of 60°C (140°F).

Determination of the fact that the temperature through the thickness of the wooden equipment has reached a minimum temperature of 60°C (140°F) can be effected in one of two ways.

In one instance a temperature sensor such as a thermocouple may be applied to the surface of the wooden equipment opposite the surface being heated in order to determine the temperature of that surface from which it can be deduced that the temperature throughout the thickness of the wooden equipment has reached the minimum temperature.

However, in a simplified version of the invention, the heat can simply be applied for a predetermined time period that has been determined, typically empirically, and possibly depending on the type of wood, possibly its moisture content, and the thickness thereof, by preparatory tests in which the elevated temperature is applied to one surface of a stave or barrel and the temperature of the opposite surface is monitored to determine a time period that would be required to achieve the purpose of the invention . That type of empirical determination of a time period could be carried out on a specific type of wood although it is also envisaged that a standard time period may be determined that would be appropriate to all wooden barrels of a particular size and therefore thickness of wall. Use of a time period of this nature appreciably simplifies the equipment used for implementing the invention. Such a time period is anticipated to be of the order of a maximum of 60 minutes; a minimum of 7 minutes and most probably about 15 minutes. The time frame will in any event depend on the external ambient air conditions and the temperature of the wood prior to placement in the chamber.

Further features of the invention provide for the said surface to have its temperature raised to an elevated temperature of between 60°C (140°F) and 74°C (165°F) and preferably to about 71 °C (160°F); for the surface to be maintained at said elevated temperature until such time as the temperature through the thickness of the wooden equipment has risen to a minimum of 60°C (140°F) and preferably about 63°C (145°F); for the wooden equipment to be a wooden wine barrel or other wooden container (hereinafter referred to collectively as a wooden barrel irrespective of its construction), especially one made of oak, or to component staves thereof; for the heating to be effected using either steam or hot water that is appropriately injected or circulated, as may be required; and for the elevated temperature to be maintained for a period of from 5 to 60 minutes and preferably about 1 5 minutes once the set-point temperature has been reached.

In a first variation of the invention, the wooden equipment may be placed in an enclosed chamber with the interior of the chamber being maintained at said elevated temperature until the temperature through the thickness of the wood has reached the said minimum temperature. In this variation of the invention, if the wooden equipment is a wooden barrel, the exterior of the wooden barrel is maintained at said elevated temperature until the temperature on the inside surface of the barrel has reached the said minimum temperature. In this instance, the barrel may be provided with a small amount of water on its inside in order to maintain adequate humidity. The temperature of the wood may be sensed at the inner surface thereof typically in a position out of contact with the water by means of a temperature sensor such as a thermocouple held temporarily in contact with the inner surface of the barrel by means of adhesive tape or any other suitable expedient.

In a second variation of the invention as applied to a wooden barrel, the temperature of the inner surface of the barrel may be raised to said elevated temperature utilizing a heating fluid such as steam or hot water and the temperature of the outside surface may then be monitored until such time as it reaches said minimum temperature. In this variation of the invention the outer surface of the wooden barrel is preferably enclosed within a heat insulating layer such as a thermally insulating blanket or the like and a temperature sensor may be held in contact with the outer surface by adhesive tape, any other suitable expedient, or simply by the thermally insulating blanket.

In a third variation of the invention the heating fluid that is typically water at said elevated temperature is heated in a circuit that includes a heat exchanger that is heated by means of steam or directly by means of electricity, gas, solar energy, or the like, and the heating fluid is circulated through the interior of the wooden barrel that is, in this instance, full of water. The wooden barrel is preferably insulated on its outer surface with a heat insulating layer such as a thermally insulating blanket or the like and a temperature sensor may be positioned between the outer surface of the barrel and the heat insulating layer.

Of course, in each of the first second and third variations of the invention, it is possible to avoid the use of the temperature sensor if the time period has been predetermined and time can then be used for heating the wood to the minimum temperature throughout its thickness.

In a fourth variation of the invention the interior and exterior of the wooden barrel are both subjected to elevated temperature. In such an instance the barrel may be filled with hot water at said elevated temperature and the barrel may be heated as envisaged above for a predetermined time period so that the temperature through the thickness of the wooden wall of the barrel has been given an opportunity to rise to a temperature above said minimum temperature. On the basis that heating will be taking place from both surfaces of the wood, it is anticipated that the time period required would be a maximum of about 15 minutes and most probably about 7 minutes. Other variations of the invention will be quite apparent to those skilled in the art in the light of what has been stated above.

In order that the invention may be more fully understood one embodiment of each of the four variations of the invention outlined above will now be described with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:-

Figure 1 is a schematic elevation of an embodiment of the first variation of the invention; Figure 2 is a schematic elevation of an embodiment of the second variation of the invention;

Figure 3 is a schematic elevation of an embodiment of the third variation of the invention; and,

Figure 4 is a schematic elevation of an embodiment of the fourth variation of the invention.

DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS

In all instances described below, oak wine barrels were washed using standard washing apparatus common to the industry prior to treatment as provided by this invention. In the variation of the invention illustrated schematically in Figure 1 , the method of the invention is applied to the treatment of wooden barrels (1 ) used for ageing or storing liquids such as wine, vinegar and other liquids that are typically produced as agricultural products. In this variation of the invention the barrel is located in a thermally insulated chamber (2) and the exterior of the barrel is maintained at an elevated temperature of about 71 °C (160°F) until the temperature through the thickness of the wood has reached a minimum temperature of 60°C (140°F).

In this instance, the barrel may be provided with a small amount of water (3) on its inside in order to maintain adequate humidity. The temperature of the wood may be sensed at the inner surface thereof typically in a position out of contact with the water by means of a temperature sensor such as a thermocouple (4) held temporarily in contact with the inner surface of the barrel by means of adhesive tape (5).

In the case of oak barrels, the bung is sealed and the barrel is then allowed to return to ambient air conditions after the treatment has been completed. It is to be noted that it is critical not to exceed 74°C (165°F) overall as this can be detrimental to the quality of the wood or oak barrel after treatment.

This method has been found to kill microbiological species that may be present in the wood and that would otherwise give rise to the danger of spoilage microbiological species, as described above.

Heating is, in this instance achieved by injecting steam into the thermally insulated chamber by way of a steam injection device (6). A control mechanism (7) may be provided for detecting when the thermocouple reaches the desired elevated temperature and also for controlling the internal temperature of the chamber to the desired temperature of about 71 °C (160°F) by controlling the flow of steam into the chamber. The control mechanism may be configured to activate an audible and/or visible signal that the target temperature has been reached and also, optionally, to automatically shut off the supply of steam to the interior of the chamber. In a second variation of the invention an embodiment of which is illustrated schematically in Figure 2, the temperature of the inner surface of a barrel (1 1 ) is raised to an elevated temperature of about 71 °C (160°F) utilizing a heating fluid which may be either steam or hot water and the temperature of the outside surface is monitored using a thermocouple (12) held on the outer surface of the barrel using a suitable adhesive tape (13). In this instance the outer surface of the barrel is heat insulated by means of a thermally insulating blanket (14) or the like. A control mechanism (15) may be provided.

In a third variation of the invention an embodiment of which is illustrated schematically in Figure 3 the heating fluid that is typically water at the selected elevated temperature of about 71 °C (160°F) is heated in a circuit that includes a heat exchanger (21 ) that is heated by means of steam or directly by means of electricity, gas, solar energy, or the like in a heater (22). The heating fluid is circulated through the interior of the wooden barrel (23). The wooden barrel is preferably insulated on its outer surface with a thermally insulating blanket (24) and a temperature sensor (25) may be positioned between the outer surface of the barrel and the heat insulating layer. The hot water is circulated for at least 1 5 minutes or until the outside surface of the barrel has reached 63°C (145°F).

In a fourth variation of the invention an embodiment of which is illustrated schematically in Figure 4, the interior and exterior of the wooden barrel (31 ) are both subjected to elevated temperature. In such an instance the barrel may be filled with hot water (32) at elevated temperature of about 71 °C (160°F) and the barrel may be externally heated in a thermally insulated chamber (33) as envisaged above until the temperature through the thickness of the wooden wall of the barrel has been given an opportunity to rise to a temperature above said minimum temperature. The time period over which heat will penetrate the wooden wall from both sides thereof until the middle of the thickness of a wall reaches the minimum temperature of, in this particular instance, about 63°C (145°F), will vary with the cellular structure of the wood that, as a general rule, in the instance of a wood such as oak and with a wall about 20mnn thick, a time period of about 7 minutes should be sufficient.

A routine test can be conducted on any particular type of wood having a particular thickness by applying heat to one side of a wooden wall and measuring the time taken for the other side of the wooden wall to reach the target minimum temperature. This would give an indication that about one half of that time period would be sufficient in the instance that heat is applied to both surfaces of a barrel having a wooden wall of that thickness and of that particular type of wood. Simply by way of example, in the instance of an oak wooden wall having a thickness of 20mm, a time period of 15 minutes is considered to be sufficient.

It will be understood that numerous variations may be made to the particular embodiments of the variations of the invention described above without departing from the scope hereof. In particular, the precise temperatures may vary according to further experimental and practical results that may be achieved and the rather specific temperatures given as examples above are not intended to be interpreted as limiting the invention in any way.

For example, in a further variation and in order to reduce time, it is possible to wrap the outside of a wine barrel with an electrically heated thermally insulated wrap. Steam could then be injected into the barrel in order to increase the temperature of the wood to about 63°C (145°F) throughout. Another method could be to fill the barrel with 74°C (165°F) water and submerge in a 74°C (165°F) water bath.

Claims

CLAIMS:

1 . A method for the treatment of wooden equipment used in the food and beverage processing industry in order to kill microbiological species that may be present in the wood, the method comprising the steps of contacting at least one surface of the wooden equipment with a heating fluid in order to raise the temperature of said surface to an elevated temperature of between 60°C (140°F) and 74°C (165°F) and maintaining said surface at said elevated temperature until such time as the temperature through the thickness of the wooden equipment has risen to a minimum temperature of 60°C (140°F).

2. A method as claimed in claim 1 in which determination of the fact that the temperature through the thickness of the wooden equipment has reached a minimum temperature of 60°C (140°F) is effected by way of a temperature sensor applied to the surface of the wooden equipment opposite the surface being heated in order to determine the temperature of that surface.

3. A method as claimed in claim 1 in which the elevated temperature is maintained for a predetermined time period that has been determined empirically for a type of wood having a particular thickness.

4. A method as claimed in claim 3 in which predetermined time period is a standard time period applicable to all wooden barrels of a particular size and thickness of wall.

5. A method as claimed in any one of the preceding claims in which the said surface has its temperature raised to an elevated temperature of between 60°C (140°F) and 72°C (162°F).

6. A method as claimed in claim 5 in which the said surface has its temperature raised to an elevated temperature of about 71 °C (160°F).

7. A method as claimed in any one of the preceding claims in which the surface is maintained at said elevated temperature until such time as the temperature through the thickness of the wooden equipment has risen to a minimum of 60°C (140°F).

8. A method as claimed in claim 7 in which the surface is maintained at said elevated temperature until such time as the temperature through the thickness of the wooden equipment has risen to a minimum of about 60°C (140°F).

9. A method as claimed in any one of the preceding claims in which the wooden equipment is a wooden barrel.

10. A method as claimed in any one of the preceding claims in which the heating is effected using either steam or hot water that is appropriately injected or circulated.

1 1 . A method as claimed in any one of the preceding claims in which the elevated temperature is maintained for a period of from 5 to 60 minutes after the desired minimum temperature has been reached.

12. A method as claimed in any one of the preceding claims in which the wooden equipment is placed in an enclosed chamber with the interior of the chamber being maintained at said elevated temperature until the temperature through the thickness of the wood has reached the said minimum temperature.

13. A method as claimed in any one of claims 1 to 1 1 in which the wooden equipment is a wooden barrel and the temperature of the inner surface thereof is raised to said elevated temperature utilizing a heating fluid and the temperature of the outside surface is monitored until such time as it reaches said minimum temperature.

14. A method as claimed in any one of claims 1 to 1 1 in which the heating fluid at said elevated temperature is heated in a circuit that includes a heat exchanger that is heated by means of steam or directly by means of electricity, gas, solar energy, or the like, and the heating fluid is circulated through the interior of a wooden barrel

15. A method as claimed in any one of claims 1 , 3 or 4 in which the interior and exterior of a wooden barrel are both subjected to elevated temperature with the barrel being filled with hot water at an elevated temperature and the barrel being heated on the outside for a predetermined time period so that the temperature through the thickness of the wooden wall of the barrel has been given an opportunity to rise to a temperature above said minimum temperature.