INDUSTRIAL AND ENGINEERING CHEMISTRY
152
Conclusions The results show that the catalytic gasolines investigated Owe their high octane numbers to a substantial absence of
the normal paraffins rather than to a high concentration of the highly branched paraffins. The presence of high concentrations of aromatics in the heavier portions of the gasoline is also important from an octane standpoint. The high ratio of isomeric to normal paraffins indicates that the thermodynamic equilibrium between the various isomeric forms has not been reached in catalytic cracking.
(8) (9) (10) (11) (12) (13) (14) (15) (16) (17)
Literature Cited Bruun, J. H., and Hicks-Bruun, M. M., Bur. Standards J . Research, 5 , 1933 (1930). Zbid., 6, 869 (1931). Donald, R. M., Can. J . Research, 18B, 12 (1940). Faragher, W. F., Morrell, J. C., and Levine, I. M., IND. ENG. CHEM.,ANAL.ED.,2, 18 (1930). Frances, A. W., IND. ENG. CHEM.,18, 821 (1926). Frost, A. V., J . Gen. Chem. (U. S . S . R J , 9, 1813 (1939); tr. by J. G. Tolpin, RefilzeT, Jan., 1941. Grosse, A. V., and Waokher, R. C., IND. ENG.CHEM.,ANAL.ED., 11, 614 (1939).
(18) (19) (20) (21) (22)
Vol. 34, No. 2
Kurtz, S. S., Jr., and Headington, C. E., Ibid., 9 , 2 1 (1937). Lewis, J. B., and Bradstreet, R. B., Zbid., 12, 387 (1940). Mulliken, S. P., and Wakeman, R. L., Zbid., 7, 59 (1935). Peterkin, A. G.,Bates, J. R.9 and Broom, H. P.7 P T O C . Am. Petroleum Znst., 111, 20, 101-9 (1939). Rossini, F. D., zbid., 111, 18,36-59 (1937); oil Gas J.,36, N ~ . 26, 193-222 (1937). Rossini, F. D., and Glasgow, A. R., Jr., J . Research Natl. B u r . Standards, 23, 509 (1939). Rossini, F . D., and Prosen, E. J. R., J . Am. Chem. Soc., 62, 2250 (1940). Rossini, F. D., Prosen, E. J. R., and Pitser, K. S., J . Research Natl. Bur. Standards, 27, 529 (1941). Serebryakova, E. K., and Frost, A. V., J . Cen. Chem. (U.S . S. R.).7. 122 (1937). , T a n z c h , ' R . E , Thomas, B. W., and Padgett, A. R., Detroit meeting, A. C. S., 1940. Thomas, C. L., Block, H. S., and Hoekstra, J., IXD.ENQ. CHEM.,ANAL.ED., 10, 153 (1938). Tongberg, C. O., Fenske, M. R., and h'ickels, J. E., IND. ENQ. CHEM.,29, 70 (1937). Uhrig, K., and Levin, K., IND.ENG.CHEM.,ANAL. ED., 13, 90 (1941). Ward, A. L., and Kurts, 8. S., Jr., Ibid., 10,559 (1938). Watson, L. M., and Spinks, W. T., Can. J . Research, 18B. 388 (1940).
.---
PRESENTED before the Division of Petroleum Chemistry at the 102nd Meeting of the AMERICANCFI~MICAL SOCIETY, Atlantio City, N. J.
Foaming Properties of Wine Method and Preliminary Results MAYNARD A. AiMERINE, LOUIS P. MARTINI, AND WILLIAM DE MATTE1 University of California, Davis, Calif.
HE foaming properties of wines, the substances which
T
cause the foam, and the stability of the foam are subjects which have received little study, although several cursory observations on foaming in wines have been made (1, 8, 9, 16, 17, 20, 23). I n contrast to beer (14,26),foaming is generally undesirable in wines, especially in carbonated or naturally sparkling wines which have 3 to 6 atmospheres of pressure. (For a possible exception see Garino-Canina, 9). Sparkling wines contain from 11 to 14 per cent alcohol, and their sugar content varies from 0.20 to 10 per cent. It is undesirable to have either head retention or a very high foam capacity in these wines, since i t makes them difficult to pour (especially if they are not thoroughly chilled), may cause undue loss of liquid from the bottle or glass, and is not customary. Head formation is greatly influenced by the gas content in beers (IC),and this is undoubtedly a factor in the excess foaming of young sparkling wines that have been prepared by bottle fermentation and have been disgorged too soon and without much loss of gas. Champagnes which have aged in the bottle on the lees for a longer period (three to five years), as is customary for the better quality French champagnes, have only a small head formation. Direct or indirect losses in carbon dioxide during aging are partially responsible. Also, substances affecting the foaminess may be derived from the yeast cells during the long aging on the lees. I n naturally sparkling wines (wines made by fermentation in closed containers), the bubbles are
small and with proper aging and the usual disgorging the pressure is sufficiently reduced so that the foam capacity is diminished and there is, in addition, little head stability. Tarantola (24)showed that fermentation a t low temperatures (5' C. or 41' F.) gives a greater foam stability in sparkling wines than is obtained in those which are fermented a t ordinary temperatures (12-16' C., 53.6-60.8" F.). Sparkling wines fermented in large tanks by the Charmat procem have reduced foam retention compared to wines fermented in the bottle (15). The use of different races of wine yeast also has an influence on the amount of foam in sparkling wines ( 6 ) . Marescalchi (16) made some observations on the foaming of Italian wines. He found foaminess to be greater if the wine were bottled for 15 to 30 days, compared to samples taken from the barrel. Increasing the alcohol content reduced persistence in foaming, especially in wines high in acid. Citric and phosphoric acids were found to increase foaming while malic, tannic, lactic, hydrochloric, and sulfuric caused little change. Succinic acid decreased foaming. Dilution with water was observed to increase the persistence of foaming. Ethyl acetate, ethyl sulfate, and glycerol were found to reduce foaming. Only qualitative data were reported in this study. A knowledge of the factors influencing foaming, particularly bubble formation, would be especially desirable for carbonated wines in which there is frequently a tendency for the dissolved gas to be lost too soon owing to large bubble size and with
February, 1942
INDUSTRIAL AND ENGINEERING CHEMISTRY
153
which difficulties are frequently measuring cylinder. As soon encountered due to excessive aa the last drop of liquid In contrast to beer, foaming in wines is objectionfoaming during pouring. passed through, the stopcock able. It occurs particularly in sparkling wines and Foaming is frequently enwas closed and the time taken. in young unfortified wines during routine winery countered in routine winery opThis time for condensing foam operations, such as racking and filtering, and in erations and may cause loss of to liquid is called t, the volume continuousand pot stills. liquid or increase the time reof liquid condensed from the Using the Ross and Clark method, the foaminess, quired to fill the container. foam during this time is b, Z, of wines has been studied. Results with about 3 Foaming occurs particularly and the volume of liquid of per cent error were obtained. No difference in the in young unfortified wines, esthe foam which finally remains foaminess produced by carbon dioxide or air was pecially in those containing unin the separatory funnel is c. noted. fermented sugar or large quanSometimes a drop of ether or Addition of glycerol, grape-seed tannin, oleanolic tities of yeast cells. Old wines amyl alcohol was used to conacid, and tannic acid to wines increased theirfoamimay foam, however, and certain dense this last foam. All ness, but sucrose, tartaric acid, acetaldehyde, 8fortified wines, particularly equipment was kept scrusitosterol, n-nonacosane, and ethyl acetate had muscatels, often have a persistpulously clean. little influence on foaminess in the amounts used ent foam. Foaming also occurs From these data the foamiat 50" F. Ethyl and amyl alcohols reduced foam during the fermentation of ness, Z, or the lifetime of an Stability. The amounts necessary to change foamiwines, particularly white wines. average bubble in the foam, ness are too large to be of practical importance. This foam contains large quanis calculated from the exA t higher temperatures tannic acid decreases tities of yeast cells and various pression: foaminess. The saponins are apparently not a facsubstances of a colloidal nature. tor in the foaminessof wines. Large amounts of foam are Red wines have a much greater foam stability t often formed when wine is 2 s than pink wines produced from the same grapes but pumped from one tank to anf c 2.303 log bC not fermented on the skins, but the difference is other. The wine coming from apparently not due to the higher tannin content filters sometimes foams. In of the red wines. filling bottlm, foaming is parFermentation at 32", So,and 91" F. yields Z is considered by Bikerman ticularly undesirable since it wines with less foaminess than those fermented (W), Ross and Clark ($I), and slows down the operation. The at 72' F. No marked difference in the foaminess Gray and Stone (11) to be a use of fillers which do not splash of musts fermented with Burgundy, champagne, true physical property of will frequently prevent this or Jerez 35A strains of Saccharomyces ellipsoideus, liquids and capable of being type of foaming. with or without addition of sulfur dioxide, was measured in a variety of ways. Foaming is also obnoxious in noted. The faster the foam condenses, operating both continuous and pot stills. The foaming is octhe smaller Z will be. Z has t h e d i m e n s i o n of t i m e casionally so persistent that suecial baffles must be con(seconds). structed in the pot still to prevent the foam from passing Using this method, tests were made upon a dry red wine over with the distillate. I n the laboratory determination from Fresia grapes of the university farm at Davis; it had the of volatile acids with the Sellier tube, foaming also occurs. following composition: alcohol 11.3 per cent, sugar 0.33, Tannin is generally used to reduce this type of foaming. tannin 0.16, total acid 0.595. According to Marescalchi (17) foam persists in low-aloohol wines, in cold wines, in wines kept on the sediment, and in sick wines. To reduce excess foaminess of table wines, he recomTABLBI. RBPRODUCIBILITY OF RESULTS BY THI Ross . ~ N D mends the addition of potassium acid tartrate, or refermentaCLARKMBTHOD tion. 80 71 74 89 74 80 1, sea. Foaming may also be reduced by racking or filtering the 64.0 37.7 47.0 49.0 40.0 b, 00. 46.2 wine. A very small amount of a surface-active agent, such as 5.0 3.9 4.4 8.0 4.0 e, ao. 5.0 33.1 83.2 32.0 34.5 33.6 32.1b 2, sea.* diglycol laurate, will usually prevent excess foaminess.
-
Experimental Procedure The method used by Ross and Clark (21) to determine the foam capacity of beer waa chosen because it dispenses with many unnecessary measurements and undue precautions, requires no arbitrary height or time interval, can be adapted t o either sparkling or still wine, and is based upon an adequate theoretical and experimental basis (6,II). The procedure consisted in placing 200 ml. of the Wine in a 1000-ml. separatory funnel and bubbling in carbon dioxide through a Chamberland porous filter until the funnel was full of foam. It was permitted to stand for about one minute before all of the liquid was withdrawn, leaving the funnel full .of foam. The volume of liquid withdrawn did not have to be measured. As soon as the stopcock was closed, the measurement of time was started, the foam was allowed to subside for a period of not over 240 seconds, and then the liquid which deposited at the bottom of the funnel was withdrawn into a
*Average 2 33.1 b Eaoh sample represents a new sample of the same wine from the same lot.
Data showing the reproducibility of the results obtained with this method are given in Table I. The percentage error is about =t3 per cent. These results are considered sufficiently close for practical purposes. These tests were made at 60" * 1' F. This temperature is slightly warmer than that at which still wines are manipulated. Foaminess is greatly influenced by temperature. No regular difference in the foam properties of wines when the foam was produced by carbon dioxide or air could be demonstrated. This is different from beers where a more stable foam was formed when air was used to produce the foam (4, 10). The greater foam produced by carbon dioxide is related to the greater solubility of carbon dioxide in beer according to Helm and Richardt (19.
INDUSTRIAL AND ENGINEERING CHEMISTRY
154
Vol. 34, No. 2:
TABLE 11. INFLUENCE OF VARIOUS SUBSTANCES ON FOAMINESS Z -Experiment t, b, cc. 38.2 18.7 58.0 53.0 46.0 34.7 35.0 38.0
sec. 75 I9 95 82 88 76 75 78
Check Ethyl alcohol, 20%b Tartaric acid 1.25% Glycerol, 5%' Sucrose 10 Acetaldkhyg, 300 p. p. m. Amyl alcohol 0.1% Ethyl acetat:, 2%
b
-Experiment t,
b,
sec. 85 20 90 88 87 82 86 75
cc. 51.5 20.1 47.5 49.0 43.5 44.0 61.5 45.0
.. .. .. .. .. .. .. .. ... .. . .. .. .. .. .. .. .. .. .. .. ..
Average I: 34.1 6.6 39.8 46.6 40.1 34.2 31.4 33.5
...
60.0
21.5 32.5 26.5 25.5
46.4 62.0 47.2 48.7
43 89 121 135
59.0 60.0 89.0 91.0
3.7 4.2 13.0 28.5
15.2 32.6 58.7 94.0
41 88 85 158
52.0 57.0 56.0 77.0
6.2 4.6 20.5 23.5
18.3 33.8 64.5 108.0
16.8 33.2 61.6 101.1
Check 108' F. Tannihacid 0 5 7 108OF Tannicaoid' 5:O :'1OSo F: Tannicacid: l O . O & 108OF.
55 53 47 31
27.0 49.0 68.0 52.0
3.8 5.7 18.0 6.5
26.3 23.4 30.1 14.1
61
57 68 32
.59.0 54.0 66.0 23.0
4.6 4.4 5.7 3.3
23.2 22.0 26.8 15.4
24.8 22.7 28.5 14.8
Check6 Grape-seed tannin 0 . 1 7 Grape-seed tannin' 0 5 Grape-seed tannin:Z:Od
37 57 67 68
55.0 51.0 48.0 56.0
2.8 2.3 2.6 4.2
12.2 18.1 22.5 25.5
36 58 65 66
48.0 64.0 53.0 61.0
4.1 3.7 2.8 4.4
14.1 19.9 21.7 24.4
13.1 19.0 22.1 24.8
... ... ...
A t 50' F. except where noted otherwise. The percentages given are those in the diluted wine: all samples were diluted in the same proportions. A new check sample was used.
Substances Influencing Foaming
form insoluble compounds with the sterols. If the saponins were an important factor in the foam-forming complex of wines, adPERSISTENT FOAM o s BOTTLE dition of sterols should O F M U S C A T E L (A S W E E T FORTIFIED DESSERT W I N E ) , DEreduce the foaminess VELOPED DURING F I L L I N a of wines. Table I1 indicates that this is not the case, and the ordinary saponins a t least appear not t o be a factor in foaminess in wines.
Various common constituents of wine may influence its foaming capacity. The results of tests with some of them are given in Table 11. Substances which caused an increase in 2: were grape-seed tannin, tannic acid, tartaric acid, glycerol, oleanolic acid and sucrose. Ethyl and amyl alcohols caused a diminution in 2, while acetaldehyde, &sitosterol, nnonacosane, and ethyl acetate seemed to cause no change within the amounts used. It was apparent, however, that the amount of change caused by most of these substances was too small to be of much use as a practical means of changing foaminess, either to increase or decrease it a t ordinary temperatures. Glycerol did increase Z markedly, while 20 per cent ethyl alcohol reduced it materially. The increase 111 foaminess caused by sucrose and tartaric acid was small. It is possible that the foam stability of certain sparkling wines may be due to their high dosage with sujar added, primarily because of its influence on viscosity. Sandera and MirEev (22) showed that highly refined sugar does not give solutions with augmented foaming properties. Tarantola ($3) suggested a possible influence of viscosity on foaming in wines. Tests with these substances a t other concentrations may show a more optimum concentration for changing 2 although probably not in the range of a practicable amount (26). The results with tannic acid are particularly interesting. At 50' F. tannic acid increases the foaminess of wines in amounts from 0.5 to 10.0 per cent. But a t 108' F. tannic acid either causes no change in foaminess or decreases it. The results with grape-seed tannin are similar. According to von der Heide and Schmitthenner ( l a ) sapon i n s occasionally occur in wines. Saponins are known to
TABLE 111. t , sec.
b,
2ac, 8, cc. 8ec. 5.2 35.5 6.7 0.0 6.2 40.1 49.1 9.8 6.0 41.2 35.6 4.8 30.3 3.2 4.2 33.0
66.0 38.0 64.0
CheckC Tannic acid 0.5% Tannic acid' 5 0 Tannic acid: l 0 : O g
6
0.0 4.6 10.0 5.4 3.6 3.6 2.0
I:, sec. 32.8 6.5 39.6 44.1 39.9 32.9 32.6 33.9
65 48 58 59
CheokC Oleanolic acid. 0 00170 @-Sitosterol 0 05% n-Nonacosa'ne, 0.001%
0
10c,
cc. 3.8
CC.
c, cc. 2,aec.
Av. 2;
FOAMINESS O F P I N K AND
Series 1 -Red49 17 42 53 44 61 2.4 6.2 0 0 5.1 4.4 20.1 15.4 4.8 17.7
-Pink20 48
Influence of Fermentation Practice This experiment was made on wines which had been fermented on and those fermented off the skins in order to produce red and pink wines. The tannin content is the chief analytical variable between the samples which were measured. I n each case the red wine has a higher z1 than the corresponding pink or white wine. The differencesin all cases, however, are much greater than would be expected from the change in tannin content alone, as indicated by the small change shown in Table I1 for wine raised to 0.5 per cent tannin from an original of 0.12 per cent. Other substances which influence Z are therefore present in the wines fermented on the skins. The results of these experiments are shown in Table 111, and the analysis of the wines used is given in Table IV. Markley, Sando, and Hendricks (18) showed that, upon hydrolysis, the bloom on Vitis labrusca grapes yielded the following: glycerol; linoleic, oleanolic, oleic, stearic, pal-
REDCARIGNANE
YPink81 42 65 49 1.8 2.8 14.4 18.0 16.2
W I N E S AT
Series 2 -Red135 130 37 46 5.0 3.4 66.0 54.7 55.3
60'
&
P -nik-
l o F.
Series 3 -Red72 73 89 91 44 41 55 55 4.0 3.8 4.5 3.4 28.8 29.7 34.2 33.7 29.2 33.9
INDUSTRIAL AND'ENGINEERING
February, 1942
TABLEIv. ANALYSISO F Series 1 2 3
Garino-Canina Total Acid, % 0.75 0.76 0.54 0.57 0.56 0.50
5
1
Alcohol,
%
Extraot,
Tannin,
2.6 2.6 2.5 2.5 2.7 2.3
0.14 0.05 0.11 0.03 0.13
13.0 13.0 11.8 11.4 11.5 12.1
%
are obtained in higher concentrations by fermentation on the skins. The nitrogen content of g r a p e s fermented on the s k i n s is also higher, and identification of the n i t r o g e n fractions, p a r t i c u larly of the proteins, may also yield useful information. A detailed study of the influence of temperature of fermentation, yeast strain, and u s e of s u l f u r d i o x i d e with foaminess was carried out with M u s c a t e l of Alexandria grape juice. Twentytwo samples were fermentedat 3 2 O , 5 5 O , 72', a n d 91' F . w i t h
%
0.06
The two wines in each series were prepared from grapes harvested from t h e same field at the same time.
ANALYSISZ TABLE V. MEANOF FOAM Foaminess
7
Tzmy., 32 55 72 91
Son 16.8 19.9 32.4 7.7
...
18.8
Mean23.0
8,
Champagne 13.0 16.3 27.8 10.1 16.8
No SO2 12.4 18.1 25.7
155
(7) f o u n d that gums and pectins
PINE AND RED CARIGNANE WINES"
No. of Days on Skins 3 1 4 0
Color Red Pink Red Pink Red Pink
CHEMISTRY
Seconds Burgundy 18.4 21.7 23.0 6.4 17.4
Jerez 35A 12.4 19.2 23.8 6.7 15.5
Mean 14.6 19.0 30.4 7.7
...
mitic, and higher saturated fatty acids; nonacosane, hentriacontane, and sitosterol; small amounts of primary alcohols of the series CzOto Cs2; and unidentified resinous substances. The influence of these materials on foaminess is doubtless complex, and glycerol and the fatty acids do influence foaminess. The differences in foaminess between different wines is not due to these substances, since the change in amounts of these present in the various wines is too small to account for the changes in foaminess. Tests were also made on 10 per cent alcoholic solutions of 0.001 per cent oleanolic acid, 0.005 per cent P-sitosterol, and a-nonaoosane. When added to wine, only oleanolic acid increased foaminess (Table 11). The amounts given are practically saturated solutions.
TABLE VI. ANALYSISOF WINESFERMENTED WITH VARIOUSYEASTS AND TREATMENTS AT DIFFERENT TEMPERATURES Yeast
Champagne Champagne Burgundy Burgundy
Treatment
Total Volatile Acid@ Acid6 Gram/lOO ml.
pH
Alcohol VoZ. %
Glyoerol Extraot -Qrama/100
Sugar"
Z
m2.m
Sec.
son
Control
0.61 0.65
Temperature, 32O F. 0.066 3.45 14.3 0.081 3.52 15.1
0.75 0.78
2.7 1.8
1.81 0.73
14.2 11.8
son
Control
0.59 0.063
0.70 0.078
3.40 3.42
16.2 14.6
0.80 0.80
1.8 2.1
0.31 0.29
22.2 14.7
3.44 3.44
Jerea 35A Jerea 35A
Control
so2
0.65 0.67
0.060 0.084
17.0 14.9
0.64 0.74
1.6 2.2
0.25 0.81
14.0 10.8
Champagne Champagne
son
0.69 0.62
Temperature, 55' F. 0.066 3.41 14.3 0.048 3.50 13.9
0.92 0.95
2.6 2.7
0.68 0.57
15.9 16.8
Burgundy Burgundy
Control
son
0.66 0.62
0.076 0.063
8.45 3.44
14.6 14.5
0.79 0.78
2.8 2.8
d.67
28.7 14.6
Jerez 35A Jerez 35A
son
Control
0.69 0.66
0.036 0.048
3.43 3.40
14.5 14.8
0.87 0.87
2.7 2.4
0.37 0.64
15.1 22.6
Champagne Champagne
so2
Control
0.71 0.68
Temperature, 72O F. 0.036 3.40 13.7 0.060 3.41 14.9
0.83 0.81
2.9 2.7
0.51 0.25
21.1 34.6
Burgundy Burgundy
son
Control
0.66 0.59
0.036 0.060
3.41 3.49
14.6 14.8
0.77 0.96
2.4 2.7
0.14
...
36.9 9.2
Jerea 35A Jerea 35A
80% Control
0.67 0.69
0.042 0.078
3.38 3.44
15.0 14.9
0.82 0.85
2.8 2.7
6.22
47.0 33.6
son
0.71 0.72 0.73
Temperature, 91' F. 0.055 3.31 11.7 0.072 3.26 11.9 0.051 3.29 12.4
0.92 0.94 0.91
6.05 5.71
Ch 8mp agn e Burgundy Jerez 35A 0
As tartaric.
Control
SOa b
As aoetic.
0
As dextrose.
6.05
3.55 4.05 3.55
10.1 6.5
6.7
APPARATUSFOR DETERMINING FOAM Carbon dioxide wine and Berkfeld filter (above); after i minites of carbon dioxide delivery (below).
156
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 34. No. 2
face-active substance. I n effect this is an envelope around the bubbles and prevents them from coming together and coalescing into larger bubbles. The substances which form this envelope are located chiefly a t the surface of the liquid. Such substances lower the surface tension, and this concentration on the surface layer is called "adsorption". It is this adsorption of material a t the surface of the liquid that is partially responsible for the stability of the foam. The results obtained by the experiment reported in Table V emphasize the fact that materials collecting a t the surface are responsible for the stability of the foam. The bubbling of gas through the wine collects these substances, and they are carried in the foam. The hop resins, which are partially responsible for foaming in beer, can be practically quantitatively removed by this means (19). What these substances are in wines must be determined by further investigation. The nitrogen compounds of wines are very complex and are being studied. Garino-Canina (8) mentions some of the common colloidal substances in wine which affect foaming but does not measure their specific influence on foaminess. They are not present in any large amount because two wines of about the same analysis, as far as the major measurable constituents of wine are concerned, may give a great difference in foam stability. I n beer the albumoses, dextrins, and hop resins have been shon-n (11, 19) to be mainly responsible for foaminess. While a large difference in surface tension will change the stability of foam greatly, most beers have a surface tension which varies only slightly, yet their foaming properties are Other Practices Influencing Foaminess sometimes very different (11). This is probably true with wines also, although evidence on their surface tensions is The fact that, once having foamed, the liquid is no longer meager. Tarantola ( I S ) , for example, found that wines capable of returning to its original foam capacity is well known whose foam stability varied considerably had practically the in the beer industry (6). The foam capacity of the same wine same surface tension. The effect of alcohol on the foam was determined six successive times with the results shown in also shows the lack of direct relation between foaminess and Table VII. The foam was not returned to the liquid. surface tension. Alcohol lowers the surface tension; therefore the foam stability should be greater, but it is actually less. That it is not greater is due to the quantities added, t o OF SUCCESSIVE FOAM DETERMINATIONS the displacement of substances causing foaming from the TABLE VII. INFLUENCE AT 60" =!= 1' F. ON 2 interface (65),to its influence on the vapor pressure, etc. 67 68 66 65 64 t 0ec. 67 The fact that red wines have a much greater foam stability 35.2 33.1 39.0 45.0 37.6 30.2 b,' co. 4.5 4.2 3.8 3.0 4.0 6.2 0, 00. than white wines made of the same grapes, grown in the same 17.5 27.4 21.5 28.3 35.3 30.1 C , sec. place, and of about the same analysis, would indicate that the longer fermentation on the skins results in the extraction of a greater quantity of foam-producing materials from the That some such substance affecting Z is present is indicated grapes. by this experiment. If alcohol were lost by the treatments, one would expect Z to increase. The results, however, show a Acknowledgment successive decrease after each determination. It is unlikely that volatile substances which greatly increase Z are present. We are indebted to K. S. Markley, of the Southern Regional The removal of the foam during the initial fermentation, as Laboratory, U. S. Department of Agriculture, for the sampracticed in some California wineries with the musts destined ples of oleanolic acid and n-nonacosane used in the experifor sparkling wines, is apparently partially based on the dements reported in Table 11. sire to rid the wine of some of the substances causing foaming. The usual practice is to fill the fermentation container too Literature Cited full and allow it to foam over during the fermentation. (1) Anonymous, W i n e s and V
