GB2204878A

GB2204878A - Method of manufacturing whisky

Info

Publication number: GB2204878A
Application number: GB08810316A
Authority: GB
Inventors: Leslie Ian Kerr Ebbutt; Robert Norman Maclean; John Henderson Brown
Original assignee: United Distillers PLC
Current assignee: United Distillers PLC
Priority date: 1987-04-30
Filing date: 1988-04-29
Publication date: 1988-11-23
Anticipated expiration: 2008-04-29
Also published as: GB2204878B; GB8710250D0; GB8810316D0

Abstract

Grain spirit is obtained by the distillation of "wash" in the manufacture of whisky, and it is very important that the spirit should be of constant quality with regard to its taste and smell. One of the most common causes of significant departure from such constant quality is the presence in the spirt of "B" compound which is 2-methyl-3(methyldithio) furan and which imparts a burnt odour to the spirit. This problem is overcome by introducing oxygen into the wash by providing a compressed air supply to the feed pipe (12) to a rectifier (16) of a Coffey still (18). The incidence of "B" compound is thereafter found to be insignificant. <IMAGE>

Description

Method of Manufacturing WhiskY This invention relates to the reduction of undesirable flavour components in grain spirit.

Grain spirit is obtained by the distillation of "wash" in the manufacture of whisky, and it is very important that the spirit should be of constant quality with regard to its taste and smell. One of the most common causes of significant departure from such constant quality is the presence in the spirit of "B" compound which is 2-methyl3(methyldithio) furan and which imparts a burnt odour to the spirit.

Hitherto the presence of "B" compound was generally associated with the use of newly-commissioned rectifiers in the Coffey still and was dealt with by closely controlled short distillation runs. It is believed that the more frequent shut downs of the still allowed the oxidative capacity of the still to recover.

However, the presence of "B" compound reappears from time to time for some as yet unidentified reason at which times the traditional steps of reducing the problem, such as reflux control and shorter distillation runs, has not satisfactorily arrested the problem.

Further, it is uneconomic to stop the distillation process frequently to allow the still's capacity to remove "B" compound to be restored.

According to the present invention there is provided a method of manufacturing whisky in which oxygen is introduced into the wash. The oxygen enhances the natural oxidative capacity of the still, and can be introduced in the form of, for example, gaseous oxygen, or air, or water which is saturated with air or oxygen.

The introduction is preferably made prior to the wash entering the Coffey still, although it may be effective when made during passage of the wash through the rectifier stage.

Introduction is preferably made through a branch pipe into the wash supply pipe to the Coffey still.

The introduction is preferably made while the wash is at its fermentation temperature, or at a slightly higher temperature.

Preferably also, the introduction is made in an area where turbulent flow occurs, to ensure mixing of the introduced medium and the wash.

The rate of introduction of air is preferably at 100 litres of air at A.T.P. per 1000 litres of wash, but above a minimum of 40 litres per 1000,litres of wash.

Embodiments of the present invention will now be described with reference to the accompanying drawing which is a flow diagram of the manufacture of grain whisky using the present method.

Referring to the drawing, the apparatus shown is generally of a standard form in the manufacture of grain whisky, and the following description will therefore be directed to the area in which introduction of air is made in accordance with the invention.

Wash, which is the fermentation product in whisky manufacture, is contained at 320C in a receiver 10 which has an outlet pipe 12 leading to a pump 14. The pump 14 supplies wash through the pipe 12 to the upper end of a rectifier 16 of a Coffey still 18 and the wash passes downwardly through the rectifier 16 being preheated as it does so. From the bottom of the rectifier 16 the heated wash is led through a pipe 20 to the upper part of an analyser 22 of the still 18 into the bottom of which steam is introduced through a pipe 24. The wash is vaporised and passes out of the analyser 22 through a pipe 26 to the bottom of the rectifier 16.The vapour passes upwardly through the rectifier 16, being cooled and fractionally condensed as it does so by heat exchange with the wash from the receiver 10, until it reaches a height in the rectifier 16 at which its alcohol concentration is at the required strength; it is there led out of the rectifier 16 through an outer pipe 28 for cooling and maturing.

In these embodiments of this invention, air was introduced continuously into the pipe 12 at A, then at B, and then at D at a rate of 100 litres at A.T.P. per 1000 litres/hour of wash flow. The air was fed along a pipe 30 from a compressed air supply and through a pressure regulator 32, a control valve 34, a rotameter 36 and a non-return valve 38.

In each case it was found that the incidence of "B" compound in the grain spirit collected from the outlet pipe 28 of the rectifier 16 was reduced to consistently insignificant levels. As A, B and D are each at the discharge area of the pump 14 the temperature of the wash was around 320C and the high pressure and turbulence of the wash flow ensured good absorption of the air.

The benefits (i.e. low "B" compound) became apparent the week following the introduction of aeration.

Average "B" compound concentration before the introduction of air was 0.14 p.p.l09 (number of samples = 166). Average "B" compound concentration after the introduction of air was 0.03 p.p.l09 (number of samples = 107).

The results were confirmed by a nosing panel, and both the nosing panel comments and "B" compound concentrations were subjected to a statistical analysis. The results showed that: (i) The levels of "B" compound found were significantly higher before the introduction of air than after the introduction of air.

(ii) The percentage of comments by the nosing panel' indicating the presence of "B" compound and made during organoleptic assessment were significantly higher before the introduction of air than after the introduction of air.

A further test was carried out to illustrate that it was the oxygen in the air introduced that was effective in reducing "B" compound. In this test air was first turned off until "B" compound was noted by nosing the grain spirit. This took 6 h hours. Nitrogen was then applied at the same gas rate as air for 4 hours and at no time during the 4 hours was the "B" compound not noticeable by nosing. Air was then restarted and the spirit improved until "B" compound was no longer noticeable by nosing. The table below gives the results of analysis for "B" compound during this period, confirming the nosing results.

AIR ON : "B" compound - not detectable AIR OFF for 6 hours : - 0.13 p.p.b.

N2 ON for 4 hours : - 0.43 p.p.b.

Air ON for 6 hours : - 0.01 p.p.b.

Modifications and improvements may be made without departing from the scope of the invention.

Claims

1. A method of manufacturing whisky wherein the method includes. the step of introducing oxygen into the wash.

2. A method of manufacturing whisky as claimed in Claim 1, wherein the oxygen is introduced in gaseous form.

3. A method of manufacturing whisky as claimed in Claim 1, wherein the oxygen is introduced in the form of water saturated with air or oxygen.

4. A method of manufacturing whisky as claimed in any one of the preceding Claims, wherein the oxygen is introduced to the wash prior to the wash entering a Coffey still.

5. A method of manufacturing whisky as claimed in Claim 4, wherein the oxygen is introduced through a branch pipe into the wash supply pipe to the Coffey still.

6. A method of manufacturing whisky as claimed in any one of Claims 1 to 3 wherein the oxygen is introduced into the wash during passage of the wash through the rectifier stage of a Coffey still.

7. A method of manufacturing whisky as claimed in any one of the preceding Claims, wherein the oxygen is introduced to the wash when the wash is at its fermentation temperature or above.

8. A method of manufacturing whisky as claimed in any one of the preceding Claims, wherein the oxygen is introduced to the wash in an area when turbulent flow occurs.

9. A method of manufacturing whisky as claimed in any one of the preceding Claims, wherein the oxygen is introduced to the wash as air at A.T.P. at a rate greater than 40 litres per 1000 litres of wash.

10. A method of manufacturing whisky as claimed in Claim 9, wherein the oxygen is introduced to the wash as air at A.T.P. at a rate of 100 litres per 100 litres of wash.

11. Apparatus for use in the method of any of the preceding Claims, comprising a compressed air supply, a pressure regulator, a control valve, a rotameter and a non return valve.

12. A method of manufacturing whisky substantially as hereinbefore described with reference to and as shown in the accompanying drawing.