WO1993016168A1

WO1993016168A1 - Procedure and apparatus for producing whisky

Info

Publication number: WO1993016168A1
Application number: PCT/FI1992/000042
Authority: WO
Inventors: Olavi LEPPÄNEN; Raimo Laakso; Michael A. Webber
Original assignee: Oy Alko Ab; William Grant & Sons Distillers Ltd.
Priority date: 1992-02-14
Filing date: 1992-02-14
Publication date: 1993-08-19
Also published as: AU1277492A

Abstract

The invention relates to a procedure for producing whisky and equivalent alcoholic beverages with low ethylcarbamate concentration, the raw material being mashed, subjected to fermentation and distilled to yield a distillate which is processed to become a finished alcoholic beverage, wherein the distillate is conducted into a cyanide compound separator column, from the head of said separator column is removed a distillate containing cyanide compounds in abundance, and the product obtained on the bottom is conducted towards further processing. Further the invention relates to an apparatus for producing whisky or equivalent distilled alcoholic beverages, comprising mash distilling apparatus (1), and a cyanide compound separator column (2), wherein the distillate is carried to the cyanide compound separator column, the distillate of which is removed, and the bottom product is conducted towards further processing.

Description

PROCEDURE AND APPARATUS FOR PRODUCING WHISKY

The present invention concerns a procedure for producing whisky and equivalent distilled alcoholic beverages, as defined in the preamble to Claim 1. Furt¬ hermore, the invention concerns apparatus for implemen¬ ting said procedure, as defined in the preamble to Claim 8.

The invention concerns in particular a proce- dure and apparatus for producing whisky with low ethyl¬ carbamate concentration.

Ethylcarbamate is inherently present in small quantities in all alcoholic beverages. This compound is formed as a result of microbial metabolism. However, certain distilled beverages, such as whisky, have been observed to contain significantly more ethylcarbamate than is formed in natural fermentation (Mildau,G. et al., Deutsche Lebensmittle-Rundschau,1987,vol.83,p. 69- 74). Ethylcarbamate is considered to be a carcino¬ gen. The principle is generally accepted that its con¬ centration in alcoholic beverages should be as low as possible. In Canada the maximum concentration limit of 150 ppb (150xl0^~5 g/1) has been imposed on distilled alcoholic beverages such as whisky. In the U.S.A. the voluntary maximum concentration of ethylcarbamate has been fixed at 125 ppb. According to a study (Clagg, B.S. et al.. Bulletin of Environmental Contamination and Toxicology, 1988, Vol. 41, p. 832-837) nearly half of the U.S. Bourbon whisky surpasses the ethylcarbamate concentration of 150 ppb. The ethylcarbamate concentra¬ tion of Scotch whisky is usually less than 15-115 ppb. Concerning scotch grain distillate a regres¬ sion line has been reported (Aylott, R.I. et al., Jour- nal of the Institute of Brewing, 1990, Vol. 96, p. 213- 221) representing the ethylcarbamate concentration in the cask. EC = 0.5 MC + 15 ppb where EC is the ethylcarbamate concentration in a dis¬ tillate (43% by vol) sample after 3 months ageing, in ppb units, and MC is the cyanide concentration in the freshly distilled distillate (94% by vol.) in ppb units.

The object of the present invention is to pro¬ vide a novel procedure for producing whisky and equiv¬ alent distilled alcoholic beverages yielding an alco- holic beverage with lowest possible ethylcarbamate con¬ centration.

It is a further object of the invention to provide corresponding, novel apparatus for producing whisky and equivalent distilled alcoholic beverages. Although the invention is hereinafter descri¬ bed with specific reference to ethylcarbamate, it is to be understood that the principles of the invention are also applicable to produce an alcoholic beverage with low concentration of aldehydes, diacetyl and many vola- tile sulphur compounds like mercaptans, dimethyl sulp¬ hide, dimethyl disulphide and dimethyl trisulphide.

The invention is based on the observed fact that fresh whisky distillate contains no significant amounts of ethylcarbamate. On the other hand, the ethylcarbamate concentration of barreled distillate has been found to increase during the first three months. The total cyanide concentration of the distillate has been found to diminish at the same time. In other words, the cyanides in the distillate appear to be con- verted to ethylcarbamate in the course of storage. The same phenomenon is known in distillates produced by continuous distillation as well as those made by pot distillation.

In the invention a procedure has been worked out by applying which the total cyanide concentration of the distillate formed in distillation can be mini¬ mized. In that case the ethylcarbamate concentration, which depends on the cyanide concentration, cannot rise to undesirable level in connection with ageing.

The formation of cyanide compounds in the mash column can be enhanced by performing the distillation under reduced pressure, whereby the boiling temperature of the mash in the column, and on the bottom of the column, is significantly lower than 100°C. There will then be fewer thermal decomposition reactions, compared with a column under normal pressure, and the distillate obtained from the mash column will contain less cyanide compounds. It is thus understood that the use of sub- atmospheric pressure in the mash column reduces, on the whole, the formation of cyanide compounds in the dis¬ tilling system, and correspondingly the total cyanide concentration of the product will also be lower in that case. In later treatment steps only minor quantities of ethylcarbamate can then be formed in the product.

Distillation in the rectification column may equally be carried out under subatmospheric pressure. When the vapor exiting at the head of the mash column is conducted to the rectification column in vapor form and the condensers on the head of the rectification column are connected to a vacuum system, the rectifica¬ tion column will operate under subatmospheric pressure and it will also maintain the mash column at subatmo¬ spheric pressure. Owing to this reduced pressure, dis¬ tillation takes place at subnormal temperature and the thermal decomposition reactions are less in the distil¬ ling process, whereby the forming of cyanide compounds is less in the distilling system, as was said in the foregoing.

In the procedure of the invention the total cyanide concentration of the distillate is also suc¬ cessfully lowered by conducting the distillate into a separator column and removing from its head an impurity fraction containing cyanide compounds in abundance, whereby the low-cyanide product gained as bottom pro- duct of the separator column can be conducted, as it is, to further processing steps. The distillate con¬ ducted to the separator column may be produced by con¬ tinuous distillation or by pot distillation (batch process) .

The reflux ratio of the separator column is advantageously made high, i.e., in the separation step a very small fraction should be withdrawn. The reflux ratio is greater than 5, advantageously greater than 10. Cyanide compounds present high relative volatility compared with ethanol, and it is therefore possible to remove an impurity fraction concentrated in respect of cyanide compounds, from the head of the column. Thanks to the invention, it becomes possible with the aid of a separator column to remove cyanide compounds from the distilling system in controlled manner and to leave, all the same, those compounds in the product which have an influence on the whisky flavor.

The removal of cyanide compounds reduces the quantity of ethylcarbamate that will form in the pro¬ duct in any subsequent process steps.

Removal of cyanide compounds by using a sep¬ arator column, as taught by the invention, may for in¬ stance be implemented in that the distillate coming from the mash column is conducted into the separator column and the bottom product of the separator column is further conducted to a rectification column, to be concentrated to desired strength.

If desired, the procedure of the invention may equally be implemented in that the distillate obtained from the head of the mash column is conducted to the rectification column, the distillate from the latter being conducted to a separate separator column for re¬ moval of cyanide compounds after the rectification col- umn. The actual product is then gained as the bottom product of the separator column.

The procedure is particularly fit to be used in manufacturing whisky, and other products made in equivalent manner. Scotch whisky is understood in this context to mean an alcoholic beverage which has been produced in Scotland by distillation, from mash derived from grain and saccharified by malt diastases, and sto¬ red in casks three years at a minimum.

American whisky is understood to be an alcohol distillate obtained by distilling mash produced from fermented grain to distillate concentration less than 95% (190° proof) in such manner that the distillate has the taste, flavor and other properties of whisky. Bour¬ bon whisky, rye whisky, wheat whisky, malt whisky or rye-malt whisky are understood to be whiskeys obtained by distilling mash produced from grain by fermentation to less than 80% (160° proof) and stored at a concen¬ tration not over 62.5% (125° proof) in new oak casks. Neutral grain spirit or alcohol is alcohol distilled from any kind of cereal, concentration 95% (190° proof) or higher, either at reduced concentration or as it is. Blended whisky is understood to be a mixture containing at least 20% whisky proper (50%, 100° proof) and, sepa¬ rately or in combination, whisky or neutral grain spir¬ it.

Canadian whisky is understood to be an alco- holic beverage which has been produced in compliance with Canadian law and contains no distilled spirits younger than three years.

Irish whisky is understood to be whisky pro¬ duced in the Republic of Ireland or in North Ireland in compliance with Irish law, for consumption, containing no distilled spirits of age less than three years.

The apparatus of the invention comprises a particular separator column for eliminating a fraction containing cyanide compounds. The separator column has been disposed in such manner that the distillate, ob¬ tained by continuous distillation or by pot distilling, is conducted to said separator column. Thus, the sepa- rator column is advantageously disposed so that the distillate from a conventional, e.g. multi-plate or packed column is conducted directly to the separator column. The rectification column may then be disposed in conjunction with the separator column in that the bottom product of the separator column is conducted directly to the rectification column.

In another embodiment, the separator column is disposed in conjunction with the distillate line of the rectification column so that the distillate of the rec¬ tification column is carried to the separator column, the bottom product of the latter constituting the pro¬ duct for further processing, in this case.

The invention is described in detail in the following with the aid of embodiment examples, refer¬ ring to the attached drawings, wherein:- Fig. 1 presents in a schematic diagram the relationship between cyanide compounds and ethylcarbamate during storage of distillate, Fig. 2 presents an embodiment of the procedure and apparatus of the invention, in which concentration takes place after cyanide compound separation, Fig. 3 presents another embodiment of the procedure and apparatus of the invention, in which separation of cya- nide compounds is effected after concentration, and

Fig. 4 displays the dependence of cyanide compounds on distilling temperature.

Fig. 1 illustrates the formation of ethylcar¬ bamate during the first four months of storing distil- late made from grain. During the same period the cya¬ nide concentration in the distillate goes down in equivalent amount. The distillate is meant to be used in producing whisky.

In Fig. 2 is depicted the principle diagram of a distilling procedure and process according to an em¬ bodiment of the invention. The figure reveals a dis¬ tilling apparatus 1 meant for mash distilling, compris- ing in the embodiment here shown, a conventional mash column 1. The distillate obtained from the mash column is conducted to a special separator column 2, the pro¬ duct from the bottom thereof being conducted towards further processing, in the present embodiment to a rec¬ tification column 3. The distillate obtained from the head of the rectification column is carried onwards to further process steps, in the present embodiment to barreling and warehousing. In Fig. 2, the mash is supplied through a feed line 6 to the first condenser connected to the head of the mash column 1, and which serves as mash pre-heater at the same time. The preheated mash is further con¬ ducted by the line 6 to the mash column 1. Typically, the mash column contains about 20 plates below, and 0-10 plates above the feed input.

To the head of the mash column is connected a condenser 8, which is connected to a vacuum system 4, by means of which the pressure in the mash column is maintained lower than the ambient pressure. Low pres¬ sure within the mash column has the effect that the boiling point of the mash in the column, and on the bottom of the column, is significantly lower than 100°C Hereby the thermal decomposition reactions taking place in the column will be few, compared with a column under normal pressure, and the distillate ob¬ tained from the mash column will contain little cyanide compounds, measured as total cyanide (MC) . A mash col¬ umn under subatmospheric pressure reduces the formation of cyanide compounds in the distilling system on the whole, and correspondingly the product will then also have a low total concentration of cyanide compounds. In that case very little ethylcarbamate can be produced in the product in any later process steps. The distillate obtained from the mash column 1 is conducted by the line 9 to a separate separator col¬ umn 2. The head of the separator column is provided with a reflux condenser 10, and the column works with a high reflux ratio, reflux ratio greater than 5. Cyanide compounds have high volatility relative to ethanol, whereby it becomes possible to remove from the head of the separator, an impurity fraction 11 concentrated in cyanide compounds.

It is possible in the system of Fig. 2 to re¬ move cyanide compounds from the distillation system in controlled manner, yet at the same time retaining those compounds in the product which affect the whisky fla¬ vor. This elimination of cyanide compounds lowers the quantity of ethylcarbamate formed in the product in subsequent process steps.

The bottom product from the separator column is conducted by the line 12 to a rectification column 3 and concentrated to requisite concentration. The pro¬ duct proper is withdrawn as head product from the rec¬ tification column, line 20.

In Fig. 3 is depicted an alternative procedure for an under-pressurized mash column. The apparatus depicted in Fig. 3 comprises a mash column 1, a recti¬ fication column 3 and a separator column 2. The distil¬ late from the mash column is fed as a vapor directly to the rectification column, and the distillate from the rectification column is fed to the separator column.

The mash column of Fig. 3 contains, typically, about 20 plates. The product is conducted by the line 6, through pre-heating 16, into the mash column 1. In this embodiment the pre-heating consists of the con- denser 16 on the head of the rectification column 3. The vapor departing from the head of the mash column is conducted in vapor form by the line 15 to the rectifi¬ cation column 3. The head of the rectification column is provided with condensers 16 and 17; the condensers are connected to a vacuum system 5. In this version the rectification column 3 operating under subatmospheric pressure also maintains subatmospheric pressure in the mash column 1. The effect is the same as that of the procedure illustrated by Fig. 2.

In the system of Fig. 3 the cyanide compound separator column 2 cannot be disposed between the mash and rectification columns 1 and 3. A separate separator column 2 has in this alternative been placed after the rectification column 3. The concentrated distillate taken out from the rectification column is conducted to the separator column by the line 18, and the product proper is withdrawn as bottom product from the separa¬ tor column, line 20. The effect is the same as that of the procedure illustrated by Fig. 2.

The distilling systems presented in Figs 2 and 3 have been depicted as plate columns. The systems can equally be implemented using columns with random pack¬ ing or high efficiency packing or with any combinations of plate columns and packed columns. Furthermore, the distilling columns shown in the figures are generally provided with boilers, e.g. the boilers 21, 22 and 23 in, respectively, the distilling column 1, separator column 2 and rectification column 3.

EXAMPLE 1: Effect of mash column operating under subatmospheric pressure

Using barley malt for raw material, mashing and fermen¬ tation were carried out with laboratory apparatus. After fermentation, the mash had ethanol concentration 4.79% w/w. The mash was divided into six 1 kg batches and each batch was distilled with a Fisher Labodest 102 precision distilling apparatus, designed for laboratory use.

The distilling apparatus comprised a distill¬ ing flask 3 1, a packed column with packing made of stainless steel, a reflux condenser, cooled by means of a refrigerating liquid circulation at -2°C, and cont¬ rols for the reflux ratio. The distilling apparatus was connected to a vacuum control system enabling the pressure in the dis¬ tilling column to be regulated within ±10 mbar.

The reflux ratio was 2 in the distilling tests. The boiling rate was adjusted so that each dis¬ tillation took 20+1 min. About 70 g of distillate were collected in the distilling test.

Each distilling test was carried out under identical conditions in all respects except that the distilling pressure was varied, The distillate was ana¬ lyzed for ethanol and total cyanide compound concen¬ tration.

The results are shown in Fig. 4. The ethanol concentration of the distillate was nearly constant between tests, indicating that the distilling tests had indeed taken place in nearly identical conditions. According to the test results, the total cyanide com¬ pound concentration goes down abruptly when the boil¬ ing temperature of the mash on the bottom of the dis- tilling column goes down.

The results reveal that it is possible by low¬ ering the pressure in the mash column -- and at the same time the boiling temperature in the mash column -- to reduce the cyanide compound concentration of the distillate obtained from the mash column. This will correspondingly also reduce the cyanide compound con¬ centration of the product obtained from the entire sys¬ tem. As has been set forth under item 2, only small amounts of ethylcarbamate can be formed in the product at any later stage.

EXAMPLE 2: Operation of the cyanide compound separator The distillates described in Example 1 were lumped to- gether and redistilled with the distilling apparatus described in Example 1.

The distilling pressure was 1050 mbar in the test and the reflux ratio was 20. 10 g of distillate were recovered. The ethanol, methanol and MC concentra¬ tions of the solution to be distilled, the distillate and the bottom product of the distillation were deter¬ mined by analysis. The results are presented in Table 1.

Table 1: Operation of the cyanide compound separator

The results reveal that the cyanide compounds can be separated as a concentrated side flow from the ethanol by using a separator column. It is also calcu- lable from the results that the cyanide compounds for¬ med in whisky distillation are highly volatile. Their volatility relative to ethanol is about 20. No prior measurements exist of the relative volatility of the cyanide compounds which are produced in whisky-making.

Claims

1. A procedure for producing whisky and equivalent alcoholic beverages, the raw material being mashed and subjected to fermentation and distilled to yield a distillate which is processed to become a fin¬ ished alcoholic beverage, characterized in that the distillate is conducted into a cyanide compound separa¬ tor column, from the head of said separator column is removed a distillate containing cyanide compounds in abundance, and the product obtained on the bottom is conducted towards further processing.

2. Procedure according to claim 1, character¬ ized in that the reflux ratio of the separator column is higher than 5, advantageously higher than 10.

3. Procedure according to claim 1 or 2, char¬ acterized in that the bottom product from the separator column is concentrated in a rectification column.

4. Procedure according to claim 1 or 2, char- acterized in that the distillate is distilled in a rec¬ tification column and the distillate from the recti¬ fication column is conducted to the separator column.

5. Procedure according to claim 4, character¬ ized in that the distillation in the rectification col- umn is carried out under subatmospheric pressure.

6. Procedure according to any one of claims 1-5, characterized in that the mash distillation is carried out under subatmospheric pressure.

7. Procedure according to any one of claims 1-6, characterized in that the temperature in the mash distillation is lower than 95°C, advantageously lower than 90°C, most advantageously lower than 85°C.

8. Apparatus for producing whisky or equival¬ ent distilled alcoholic beverages, comprising mash dis- tilling apparatus (1) for distilling the mash to dis¬ tillate, characterized in that the apparatus includes a cyanide compound separator column (2), and that the distillate is carried to the cyanide compound separator column, the distillate of which is removed, and the bottom product is conducted towards further processing.

9. Apparatus according to claim 8, character- ized in that the apparatus comprises a rectification column (3) and that the bottom product from the separa¬ tor column (2) is conducted to the rectification col¬ umn, the product of which is conducted towards further processing.

10. Apparatus according to claim 8, charac¬ terized in that the apparatus comprises a rectification column (3) and that the distillate obtained from the mash distilling apparatus (1) is conducted to the rec¬ tification column, and that the product obtained from the rectification column is conducted to the separator column (2) .

11. Distilling apparatus according to any one of claims 8-10, characterized in that the mash distil¬ ling apparatus (1) is connected to a vacuum apparatus (4).

12. Apparatus according to any one of claims 8-11, characterized in that the rectification column (3) is connected to a vacuum apparatus (5).

13. Apparatus according to any one of claims 8-12, characterized in that the separator column (8) is provided with head reflux so that the reflux ratio is higher than 5, advantageously higher than 10.