INDUSTRIAL AND ENGINEERING CHEMISTRY
1230
wines. It has been observed that such filtrations were secured when using porous silica candle filters with candles of h e porosity; with pad filters using pads like samples 1, 2, 3, 4. 7, 12, 13, 14, and 16 (Tables I and 11); and with certain chaniber types of filters using filter aids like numbers 1, 4,6, and 8 (Table 111). In addition, a special filter aid similar to number 4, but giving a somewhat tighter filtering medium, resulted in probably the most satisfactory filtrations of this type yet obtained. As a result of the microscopic observations of over one hundred different commercially filtered but nonpasteurized wines, it was found that, when the filtration was with one of the filtering materials mentioned, complete removal of the microorganisms was effected and pasteurization was not required for their control. In certain additional cases, it was observed that, while removal of the microorganisms was obtained by filtration, a reinoculation was secured by placing the wine in nonsterile containers. This only emphasizes the need and desirability of maintaining the advantages of removal of microorgani3ms by ordinary filtration practice. Frequently it has been observed that certain previously clarified and stabilized wines nevertheless became cloudy and deposited sediment even though there was no measurable increase in iron or calcium content. Dry wines of the Haut Sauterne and ChDteau Yquem types have been more common in this respect, with sauterne, Chablis, and Riesling to a less extent. Of the fortified wines occasional trouble has been experienced with angelica and muscatel types. I n many such cases microscopic observation demonstrated that the sediment was not amorphous and from the precipitation of colloidal materials, nor were crystalline materials such as tartrates present. Rather such sediments were usually white or gray in color and were composed practically entirely of microorganism cells. The occurrence of certain types of yeast cells particularly was noted. In the majority of such cases of clouding and sedimentation, the cellular deposits were nearly free of amorphous substances. Microscopic examination of the sediments resulting from centrifuging portions of such cloudy wines demonstrated the presence of microorganisms similar to those found in the naturally formed sediments. These cloudy wines have been filtered with chamber-type filters using the special filter aid previously mentioned. Samples in sterile bottles of such filtered wines and of the corresponding unfiltered cloudy wines have been held a t room temperature for 8 months, Over 90 per cent of the unfiltered samples became more cloudy with varying but increasing amounts of sediments formed. Microscopic observations demonstrated the sediments to consist of the typical microorganism forms. Similar observation of samples of the filtered wines indicated that the originally contaminating microorganisms had been removed, and that no clouding or subsequent sedimentation developed, the wines remaining brilliantly clear.
Literature Cited (1) Cruess, W. V., Fiuit Products J.,14, 198-200 (1935,. ( 2 ) Saywell, L. G., IND.EXQ.CHEV.,26, 951-2 (1934). (3) Saywell, L. G., Deutschman, W. A , , Cunningham B B , unpublished data. REOEIVED September 24. 1935.
VOI,. 27, NO. 11
Volatile Acids of Wine )LARK M. 3lORRIS Concannon Vineyards, Livermore, Calif.
Many volatile acids in addition to acetic were reported by early workers but their presence was not confirmed by more recent investigators. It was found that sound wines contained acetic and traces of propionic acid. Diseased wines contained acetic with traces of formic acid. Little or no lactic acid was found. Older wines seem to contain acetic and traces of propionic acid. Young wines appear to contain nearly all acetic acid.
0F
OLLOWING the report by Declaux in 1865 that volatile acids other than acetic were present in wine, the volatile acids present were investigated by a number of authors. The following acids are reported as being present in the steam distillate of wine: Acetic ( 2 , 4, 7, 8,1 4 , I S , 17, 18, 19, 2 5 ) Formic (14, 43, 1 5 )
Carbonic (8) Propionic (1 8 16 18 26’
Butyrjc (la,’4,’8, iL, iY, is,2 5 ) Caproic (8) Capric (8) Caprylic ( S j
Benzoic (11) Lactic Salicylic ( 6(, I13, I j 15, f 7) Oenanthic (8) Tartronic (@a, Valerianic I S) 15) Lauric ( 8 ) Valeric ( 1 1 )
Of these, acetic, formic, propionic, butyric, and lactic are more commonly reported in the early literature. It is believed that the volatile acids of sound wines consist largely of acetic with small amounts of propionic (2, 8, 16, 18, 25), and that in diseased wine3 larger amounts of propionic acid are present together with traces of butyric. Declaux reported that in diseased wines there is a decrease in fixed acids and an increase in volatile acids; part of the volatile acids are derived from the fixed. With increase in volatile acids an increase in butyric acid occurs; as high as 0.025 gram of butyric acid per liter was reported by Declaux. However, most of the studies were of a qualitative nature and the quantitative procedures, where used, were of questionable accuracy. Furthermore there is no unanimity of opinion as to the nature of the volatile acids present in sound and diseased wines. Therefore an investigation of the nature of the volatile acids of California wines was made and the results of this study are reported here. Determination of Volatile Acids The procedure used was essentially that of Dyer (3) and Declaux (2) : Enough wine to contain about 0.5 gram of total volatile acid was distilled to one-tenth of its original volume. Some difficulty was experienced in removing all of the volatile acid. The distillate was exactly neutralized with 0.1 N sodium hydroxide to phenolphthalein and evaporated to less than 100 cc. The
IL'Ob-EMBER, 1935
IXDt-STRIAL AND EkGINEERIKG CHEMISTRY
sample was acidified with 0.333 ic' sulfuric acid to a pH of 4.1, using Bromophenol Blue, and heated to incipient boiling under a reflux condenser. The sample was then steam-distilled, and 100-cc. portions of the distillate were collected and titrated. From the distillation constant, cc. - of 0.1 W NaOH per 100 cc. of distillate ,< 100 cc. of 0.1 N NaOH for sample the relative amounts of acids present were calculated. Particular care had to be paid to maintain a constant volume during distillation and a constant rate of distillation in order t o duplicate the values of the distillation constants. The dietillation constants obtained are as follows: Actual Values-2 3
, -
.icid
1
4
.Iv. Dyer Value (3)
Stein (24)
The agreement between the distillation const,ants of mixture.< of volatile acids obtained is as follows: Sample
1
1 2
...
2
:
Dietillation Constants 2 3
, . .
2s:bo i32.50
42.31 22.09 31.10 28.10 32.10
43.04 13.21 32.60 28.90 32 90
1251
--
\Vine Type Burgundy Zinfandell Zinfandell Zinfandell Burgundy Zinfandell Zinfandell Zinfandell Burgundy Burgundy Burgundy Port Port Sherry Sherry Sherry Chablis Keisling Chablis Muscatel Tournk cuiture Uninoculated wine
Vintage
Total volatile ( 1 )
1923 1917 1927 1917 1933 1917 1934 1934 1933 1933 1933 193% 1933 1933 1917 1932 1933 1916 1929 1933
0 140 0.420 0.126 0.130 0.140 0.120 0.404 0.471 0.190 0.194 0.150 0.190 0.070 0.050 0.170 0.162 0.060 0.052 0.326
.4cids--Tannic 0 005
. .. .
0.065 0 006 0.001 0.001 0:601
. 0 001
...
0'002
0.121
1934
0 360
1934
0 070
, ,
, ,
0 005 ,
.,
ProAcetic pionic 0.147 0 470 0 130 0,143 0.144 0.124 0 420 0.50% 0,197 0.200 0.154 0.197 0.078 0 061 0 180 0 170 0.067 0.062 0.370 0 127
0 001 0 062
0.005 0 001 0 005
. 0.005 0.002 0.001 0.002 O.'OOl
. . .
Condition of Wine Sound, well-matured vinegar sour Sound Sound Sound Sound ToutnP, vinegar sour TournB, vinegareour TournB TournB Sound Tournd Sound Sound Sound Toum.4 Sound Sound Tourn4,vinegareour Sound
0.390
..
TonrnB
0,080
...
Sound
.Lverage 42.67 22.61 31.85 28.50 32.50
The results reported are the averages of closel,); agreeing duplicates or triplicates. However, because the idistillation constants often differed but slightly from that of acetic acid, the acmracy of the determination of traces of other volatile acids is not high. If it were not' for the detection of the acids by other means, the results reported would be questionable even qualitatively. There are other limitations to the method used but these have been discussed elsewhere ( 3 , 2 0 , 22, 87). It was used largely because of expediency and previous wide use. Table I shows that more volatile acid was found when 500 cc. were used and treated as outlined than was found by the official A.O.A. C. method (1). This fact was noted by Hortvet (IO), particularly in wines of high volatile acid content. He found that only 90 to 9.5 per cent of the yolatile acid was recovered by the Hortvet method. In addition to using the alcohol-free distillate wines, the untreated wines were also distilled. The results obtained by the lat'ter procedure were approximately the same as those obtained by distilling a t practically constant pH in the absence
of alcohol. However, as was to be expected, the presence of
sulfur dioxide or aldehyde affected the results. The presence of other 7-olatile acids was deterinined in the distillate (5'). The silver reduction method for formic acid suggested by Thudichum and D u p e (66') was used. This was fouiid to be as reliable and as sensitive as that of the more complicated and tedious procedure of Woodman and Rurwell (28). The tests for other volatile acid. were those given by Dyer ( 3 ) .
. h i & Found in Wines The result. obtained for alcohol-free wine cwiceiitrates are shown in Table I. Similar rewlt. were obtained for fifty samples of vine di-tilled witliout concentration and dealcoholization. Qualitative tests confirmed the presence of formic acid in diseased wines and propionic acid in soiind wines. HoTve\-er, owing to the difficulty of obtaining a reproducible distillation constant the relative amount'.; of the two acids reported are wbject to a conderable error particnlarly when in small concentrations. The diseased wines analyzed appareiit1)- contained formic a n d acetic acids rather than acetic arid propicinic arid< as ~
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INDUSTRIAL AND ENGINEERING CHEMISTRY
some of the earlier workers reported. Esau (6) has reported the production of formic acid by yeast. It was found that a sample of wine inoculated with burn6 bacteria after storage for 30 days contained appreciable amounts of formic acid but the latter was not found in the uninoculated control. Apparently formic acid may be produced both by bacteria and yeast. The sound wines contained only acetic acid with but traces of propionic. Declaux (2) reported that diseased wines contain more propionic than sound wines and that butyric acid is present in diseased wines. None of the samples analyzed contained any butyric acid. Of the seventy samples all the diseased wines showed formic acid in traces.
Acknowledgment The author acknowledges the valuable assistance of Lawrence Norton Quaccia in making a few of the distillations and of 31. A. Joslyn, of the Division of Fruit Products, University of California, for advice in conducting the investigation and preparing the manuscript. Literature Cited (1) Assoc. Official Agr. Chem., Methods of Analysis, p. 140 (1930). (2) Declaux, E., Ann. Ecole Normale superieure, 2 (1865); J. Chem. Soc., 28, 188 (1865). (2a) Declaux, E., Compt. rend., 78,1160 (1872). (3) Dyer, D. C., J . BioZ. Chem., 28,445 (1916). (4) Eckenroth, H., Chem. Rundsehau, 6 , 103 (1897).
Precipitation Rate
of Cream of Tartar from Wine Effect of Temperature G. L. MARSH AND RI. A . JOSLYh-
University of California, Berkeley, Calif.
The precipitation of cream of tartar from new wines is hastened by cold storage, the rate of precipitation depending on the storage temperature and on the type of wine. The rate is more rapid during freezing storage than in cold storage. The actual amount of cream of tartar to be removed from wine for stabilization cannot be predicted from the data available since so many factors determine the actual solubility of cream of tartar in wine.
VOL. 27, NO. 11
( 5 ) Esau, P. J., M. S.thesis in bacteriology, Univ. Calif., 1933. (6) Fonxses-Diacon, H., and Jaulmes, P., Ann.faZs., 25, 149 (1929). (7) Gayon, U., Rev.nit. biere, 6,82; 7,97 (1899). (8) Grassi-Soncini, G. (tr. by Bioletti, F. T.), Biann. Rept. Calif. State Board Viticultural Commissioners, 1891 and 1892, Appendix E . (9) Grim, F., Ann. chim. pharm., 158, 117 (1871). (IO) Hortvet, J., J. IND.ESG. CHEM.,1, 31 (1909). (11) Jaulmes, P., Ann. fals., 21, 384 (1928). (12) Kayser, E . , BdZ. SOC. chim. biol., 6 , 345 (1924). (13) Kayser, E., BUZZ. SOC. encour., 94, 93, (1894). (14) Kayser, E., Rev. Bit., 47, 70 (1917). (la) Kulisch, P., 2. Nahr.-Genussm., 15, 663 (1907). (16) Laborde, J., Compt. rend., 138, 228 (1599). (17) Mach, E., and Portele, Land, Versuchs-Stats, 37, 303 (1889). (18) Malveain, P., Compt. rend., 148,784 (1909). (19) Marpurgo, Oesterr, Chern.-Ztg., 2, 209 (1899). (20) McNair, J. B., IND. ENG.CHmr., Anal. Ed., 5 , 62 (1933). (21) Osburn, 0. L., Wood, H. G., and Werkman, C. H., IWD. ENQ. CHEM..Anal. Ed.. 5 . 247 (1933). Richmon’d, H. D . , :4nalyst,’20, 1936 (1895); 31, 324 (1906); 33, 209, 305 (1908). Sielers, F., 2. Unter. 1Vahr.-Genussm., 47,135 (1924). Stein, A , J . prakt. Chena., 88,83 (1913). Thudichum, J. L. W.,“Treatise on Wine,” p. 68, London, George Bell &- Son, 1894. Thudichum, J. L. W., and Dupre, A , , “Origin, Nature and Use of Wine,” p. 184, London, Macmillan and Co., 1872. Wilson, J. A , J . Soc. Chem. Ind., 9, 18 (1800). Woodman and Burwell, Tech. &7rart., 1, 68 (1908). RECEIVED Aueuat 28, 1935.
QT
HAT the freshly expressed juice of the grape and new wine contain cream of tartar in concentrations greater than saturation is well known. In order to avoid the undesirable precipitation of cream of tartar in the bottled wine, the excess cream of tartar is removed by prolonged storage a t room temperature or by cold storage for shorter intervals. According to the accepted laws of precipitation, the rate of precipitation of cream of tartar should depend on the velocity of formation of nuclei and on the rate of crystal growth, both of which are functions of the absolute supersaturation ( 5 ) . Since substances other than cream of tartar present in wine may serve as nuclei for crystal formation and since the solubility of cream of tartar in wine is influenced by a large number of factors, it is difficult to apply the simple precipitation laws to the study of removal of excess cream of tartar from wine. Thus, as shown in Figure 1, although there is a tendency for the cream of tartar content of California exposition wines of 1900 to decrease with increase in alcohol content, other factors are involved in determining the actual solubility. Since the solubility of cream of tartar decreases with decrease in temperature, it is to be expected that the rate of precipitation of cream of tartar should be faster a t lower temperatures. However, as shown later, the type of wine also influences the results. Continuing the study reported previously on the effect of cold and freezing storage on wine composition (g), the writers have determined the amount of cream of tartar precipitated from four typical wines stored a t various temperatures for different intervals of time, and the data observed are presented here.
Storage Tests Freshly made untreated wines of the vintage of 1934 from a winery in Lodi in the San Joaquin Valley district mere used in these tests: These consisted of a dry white wine made from Toka grape juice, a dry red wine made from a blend of Carignane and Jlicante Bouschet grapes, a port wine from a blend of about half Alicante Bouschet and half Carignane, Cornichon, and Mission, and a sherry material from fermented Tokay juice. Before use the
