A prelimi-

nary study of Changes in Whisky during Aging

the absorption of ultraviolet l i ght by

whisky was made. Seven samples of whiskies varying in

quality from an aged 6-year-old rye bourbon to a blend of alcohol with 6-month-

old whisky were studied. The results show that whisky gives a characteristic ultraviolet absorption

spectrum and that aging apparently increases the absorption. A study of the spectra of all

substances identified in whisky, to- gether with the changes that occur

over a period of years in storage, may lead to important de-

Shown in the Ultraviolet Absorption Spectra

FRANCIS EARL RAY P. 0. Box 91, University of Cincinnati Station, Cincinnati, Ohio

RIMITIVE man doubtless discovered that age improved the quality of wine during his efforts to preserve the beverage

from one harvest to another. When the still was invented, it was found possible to secure a beverage of greatly increased potency which could be kept (if desired) indefinitely, The effect of age on the palatability of the distillate was also noted, and soon age and quality became almost, if not entirely, synonymous (3, 6, 19, 14, 16).

With the advent of the modern industrial era the cost of storage became of great importance and the brain of man tried to devise methods of quick aging. The use of heat (8) during storage was the obvious method of increasing the velocity of a reaction. Unfortunately the higher tempera- tures seemed to cause other changes than those desired and the palate, that supreme court of quality, declared the product unconstitutional.

The use of chips or sawdust (10, 11, 16) and of circulatory systems (18) has been tried; chemicals have been added (6); oxygen (4, 17) , ozone (1, 9, 11, IS), and hydrogen (11) have been bubbled into the raw spirit; and electrolysis (11) has been used in an effort to speed the process. The final verdict has always been in favor of the naturally aged product. So firmly is this preference established that distillers of quality products regard all proposals for quick aging with indifference, if not with suspicion.

The reason for the failure to speed the process lies in the complexity of the changes that occur, and the author believes that, until a much more thorough understanding of the nature of these reactions is secured, such attempts are bound to fail, Better methods of analyses are needed as well as a) more careful study of the individual reactions that take place.

velopments in the manufacture

and aging of whisky.

Measurement of Ultraviolet Absorption As a contribution to this problem, a preliminary examina-

tion of the ultraviolet absorption spectra of various grades of whisky was made. The ultraviolet absorption of the samples (described in Table I) was measured by the aid of a Giirtner quartz spectrograph, and a special photographic density matching method (9). Figure 1 shows the results. The abscissas are wave lengths in Angstrom units; the ordi- nates are extinction coefficients, given by the equation:

1 Io K = - log,, - CD I1

where K = extinction coefficient C = concentration D = thickness of cell (2 cm.) 10 = light transmitted by cell and distilled water II = light transmitted by cell and whisky

The areas below the curves represent absorbed ultraviolet light; those above, transmitted light. At any wave length the ability of the undiluted whisky to absorb light of that frequency is expressed by the value of K. The values of K are given in Table 11.

A preliminary test showed that the undiluted whiskies absorb ultraviolet light so completely that measurements could not be made. Dilutions of 1 to 10, 1 to 25, and 1 to 50 were then made and photographed. The 1 to 10 dilution was still too concentrated for the entire curve to be obtained. The 1 to 50 was too dilute for accurate measurements. The 1 to 25 dilution was by far the most satisfactory, and the results can be regarded as sufficiently accurate to say that, in most regions, the differences in the curves are real and reproducible.

Notwithstanding the inaccuracv of the results obtained from the-1 to 10 and th’e 1 to 50 dilu- tions, Table I11 is given to confirm the relative

Sam- orders of absorption. The regularity thus ob- Acids as Acetic Aide- Fur- Higher served proves that the results obtained a t a dilu-

tion of 1 to 25 are by no means fortuitous, but I1 5-yr. bourbon 173.0 39.6 28 .8 60 .5 6 . 6 2 . 6 141.9 seem to represent a distinct change of absorp-

V 6-mo. straight 107.2 3 0 . 0 17 .0 2 4 . 6 2 . 9 2 . 0 132 .0 spaces in Table I11 represent absorptions too VII 26% 6-mo. and alcohol blend 146.4 15 .0 9 . 0 17 .6 1 . 1 0 . 1 5 2 . 8 large or too Small to be determined a t that wave

302

TABLE I. CHEMICAL ANALYSIS OF WHISKIES (IN Ma. PER 100 ML.)

Description Residue Fixed Volatile Esters hydes fural Alcohols F.2. I 5-yr. rye 162.0 37 .8 31 .2 5 8 . 0 6 . 0 3 . 0 137.2

I11 6-yr. rye and bourbon 152.0 40 .8 3 0 . 0 5 2 . 8 6 . 6 3 . 0 137.2 IV 15%b4-yr.and6-mo.mixture 120.8 39 .7 18 .6 2 8 . 2 3 . 2 2 .0 141.0 tion spectra with the age Of the mihisky* V I 20%4-yr.andalcoholblend 170.0 16 .5 1 0 . 8 2 2 . 8 1 .7 0 . 5 7 5 . 0

length and dilution.

MARCH, 1936 INDUSTRIAL AND ENGINEERING CHEMISTRY 303

Doints. ComDarison of TABLE 11. VALUES OF K USED IN FIGURE 1 (DILUTION 1 TO 25) ihe analysis '(Table I)

with that of the other whiskies does not show

No. 2300 2400 2500 2600 2700 2800 2900 3000 3100 3200 3300 3400 what causes t h e high Wave Length in Angstrbm Units Sample -

I . . 25.0 17.9 17.3 19.5 20.5 16.2 12.0 9.3 7.7 6.2 4.1 absorp t ion since o d y I1 , . 20.5 16.0 15.8 17.9 18.5 15.1 9.8 6.8 5.1 9.0 3.0 the volatile acids are in IV 19.0 14.7 14.0 15.3 15.8 12.2 8.3 5.8 4.3 3.6 2.0 excess over the 5-year- V 22:s 15.5 12.5 11.5 13.1 14.0 10.5 7.2 5.2 3.8 3.2 2.3 old bourbon (11), and

V I 11.8 9.0 6.9 8.0 9.7 11.0 9.4 5.6 2.8 1.9 1.1 the 6-year-old mixed bourbon and rye (111).

I11 . . 22.5 15.9 15.6 16.8 16.7 12.3 8.4 6.0 4.7 3.5 1.3

T'II 9.8 5.3 6.2 7.1 8.7 10.0 8.7 5.3 3.9 3.0 2.3 2.0

It would be interesting to determine the cause

of this high absorpt ion. It can hardly be ascribed entirely to volatile acids since these a re repor ted to

the absorption in the ultraviolet. The curves are not pro- a b s o r b l ight at the portional a t all wave lengths, showing that the result is not

Effects of Aging It is apparent from Figure 1 that age, in general, increases *

due solely to the increaseof one component. Instead, some curves touch a t certain wave lengths and deviate. widely a t others. This behavior indicates that a t least three absorbing components are present, the absorption maxima of which occur at differing wave lengths. This is especially evident in comparing aged rye and bourbon.

Although a t present the nature of the compounds respon- sible for the absorption is not known, they are probably present in rathero small amounts. The predominant ab- sorption a t 2760 A. with minimum a t 2500 A. is somewhat similar to that of propionaldehyde (7). Furfural is rather different in its absorption but may be included. Acids prob- ably account for much of the absorption a t the lower wave lengths. The curves fall mostly in the order of age:

SAMPLE I is a 100-proof rye whisky 5 years old. It has the greatest absorption and the curve has several characteristic

I I I . OOA. 2400 1 6 0 0 2800 3000 3100 : I

0

FIQURE 1. EFFECT OF AGE ON ULTRAVIOLET ABSORPTION OF WHISKIES

higher wave lengths and-would not account for t h e high values at 2800 A. Besides, sample 111 has a higher content of volati le acids than 11; yet its absorption is less except f o r values under 2600 A. Between 2350 and 2600 A. the ab- sorpt ion is about t h e same f o r samples I1 and 111.

SAMPLE I1 is a 5-year-old 100- proof bourbon. The residue is higher t h a n in sample I, as are the fixed acids, es te rs , and-higher alcohols.

SAMPLE I11 is a 6-year-old mix- t u r e of bourbon and rye . The residue is low, the fixed acids are high, and the other values are in- termediate between samples I and 11. Since it is only 90 proof, the reactions that lead t o increased absorption are evidently slower as the dilution alone is insufficient t o account for t h e lower absorp- tion.

SAMPLE IV consists of a mixture of 15 per cent 4-year-old with 6-month-old straight whisky. The residue, volatile acids, esters, and aldehydes aU run considerably be- low the completely aged whiskies.

SAMPLE V is a straight 6-month- old whisky. The low residue and aldehyde values are of interest.

SAMPLE VI is a popular blend con- ta in ing 20 per cent of &year-old whisky with alcohol. The high resi- due is accounted for by the presence of wine and caramel. Especial ly noticeable is the low absorption at 2500 A. of blends VI and VII; this behavior gives an excellent method of recognizing a blended whisky; also that t h e peaks of curves VI and VI1 are displaced to the right of those of the straight whiskies.

SAMPLE VI1 is a blend containing 25 per cent of 6-month-old whisky with alcohol and caramel.

This summary of the analytical d a t a s h o w s t h a t a chemica l analysis f a i l s t o i n d i c a t e w h y samples I, 11, and 111 give such different absorption curves. We are thus led to the conclusion that the ultraviolet absorption spectra are due to the presence of sub- stances that the ordinary chemi- cal analysis fails to identify. If these substances contribute largely to the quality of the product, the use of u l t r a v i o l e t s p e c t r u m analysis c o n s t i t u t e s a new and significant method for the investi-

- TI : : u1 . . O J

304 INDUSTRIAL AND ENGINEERING CHEMISTRY VOL. 28, NO. 3

gation of the chemical changes that occur during the aging of whisky.

Acknowledgment

(6)

(7)

(8)

(9) (10) (11)

(12) (13)

The author's thanks are due F. F. Heyroth for his help and counsel in this work.

This work on the ultraviolet absorption spectra of whiskies, though temporarily interrupted by lack of funds, will be continued.

Literature Cited (14)

(15) (16)

(17) (18)

(1) Coffre, R. , British Patent 340,647 (1928); French Patent ,

( 2 ) Decker, J., Chem. Fabrik, 1929, 49-51. (3) Fain, J. M., and Snell, F. D., IND. EXG. CHEM., News Ed., 12,

(4) Forer, A. G., Russian Patent 32,468 (1933). (5) Gasch, J. B., U. S. Patent 1,963,165 (1934).

662,348 (1928).

120-1 (1934).

RECEIVED November 12, 1935.

Hastie, S. H., and Dick, W. D., J. Inst. Brewing, 34, 477-94

International Critical Tables, Vol. V, p. 361, New York,

Jean, F., and LizBe, D., French Patents 779,311 and 779,685

Loofbourow, J. R., Bull. Basic Sci. Research, 5 , 46 (1933). Miller, S. C., U. S. Patent 1,981,873 (1935). Philipsky, Anton, German Patents 500,708 (1928), 549,524

(1929), 557,806 (1930), 572,351 (1932), and 584,855 (1933); French Patent 702,138 (1930).

Reich, G. T., Chem. & Met. Eng., 40, 618 (1933). Reinisch, E., Austrian Patents 112,976 and 115,902 (1929). Shepard, C. E., and Bailey, E. M., Conn. Agr. Expt. Sta.,

Sunderman, F., and Grant, R., Canadian Patent 303,644 (1930). Taviera, M., Filho, J., and Melo, J., Rev. soc. brasil chim., 4,

Toth, G., Magyar Chem. Foloyirat, 38, 129-34 (1932). Wilkie, H. F., French Patent 773,202 (1935).

(1928).

McGraw-Hill Book Go., 1529.

(1935).

Bull. 363 (1933).

106 (1933).

Chemical Foreign Trade in 1935

OTTO WILSON 3025 Fifteenth St., N. W., Washington, D. C.

ESPITE a greater state of political tension abroad than a t any other time since the World War, the year 1935 witnessed a con-

tinuation of the upward tendencies that have marked our foreign trade in chemical goods since 1932. The gain in im- ports was small but that in exports was of good proportions, thus repeating the story of the trade in 1934. In that year the gain in the incoming trade in chemical commodities was slightly under ten per cent and in the outgoing trade more than twenty per cent. In 1935 imports gained about five per cent over the previous year and exports eleven per cent. The spread between the two branches of the trade, which a few years ago were about the same in total value, has brought them to the point where imports are just two-thirds of exports in value.

Considering the 1923-25 trade as a fair average, our ex- ports of chemical goods are now within sight of a normal level. Another year such as the last and they will have reached practically the value of the annual exports in that period. Imports, however, are still but little more than half the 1923-25 average and are making very slow headway to- ward that mark. As compared with the high figures of 1929, both imports and exports are still making a very deliberate recovery, the 1935 total for the former being forty-eight per cent of that in the boom year and for the latter sixty-eight per cent.

As compared with the total foreign trade of the United States in 1935 the combined incoming and outgoing movement of chemical goods showed a somewhat lower acceleration.

Continue' - - 'l'r en cis

Upward

Exports of all commodities taken together were seven per cent above those of 1934 and imports were higher by twenty- four per cent. In both branches the latter part of the year brought increased activity but especially in imports which were thirty per cent larger in the last four months than in the like period of 1934. Exports were about one-fifth higher for that period.

The outstanding development in the field of the country's foreign trade in 1935, the unfolding of the State Department's new trade-agreement policy, can hardly be judged to have had much direct effect on the trade in chemicals. Agreements carrying extensive cuts in tariff rates on chemical products, either in our own schedules or in those of foreign countries, did not become effective until about the close of the year. When the returns showing our trade in 1935 with separate countries become available, it will probably be possible to trace a stimulus in our Cuban trade to the operation of the re- duced trade-agreement rates, and perhaps also in the trade with Belgium and Norway. But the chief interest of Ameri- can chemical producers and consumers will lie in the effects of agreements with countries such as Canada, the Nether- lands, and Switzerland, which did not become operative untiI the beginning of 1936 or later.

I. Chemicals and Related Products All the large groups of chemical products shared in the gen-

eral increase in export trade in 1935. In the import trade two out of the seven groups returned slight losses and all the others registered a greater volume of business than in 1934. Imports of medicinals were three per cent less and those of industrial chemicals eight per cent less, while paints and re- lated articles picked up twenty-five per cent and coal-tar products fifteen per cent over 1934. In the export trade the increases were evenly distributed, ranging chiefly from ten to twenty per cent. Toilet preparations and fertilizers showed

1 All 1935 figures are preliminary. Import figures represent imports for consumption.