Natural Aging of Wine When aged in vats, wines increased in volatile ester content. As a result of the precipitation of lees, there were decreases in combined tartaric acid and in color and tannin. Wines hermetically sealed in glass increased in volatile ester content during a year’s storage at room temperature. There was no detectable amount of a reversible Redox system at the pH of wine.
A CHEMICAL STUDY E. K. NELSON AND D. H. WHEELER Bureau of Agricultural Chemistry and Engineering, U. S. Department of Agriculture, Washington, D. C .
The results of this investigation are influenced by winery HE literature on wine is profuse, and no attempt is treatment such as racking, sulfuring, and addition of wine to made here to review it thoroughly. Some interesting take care of ullage. They are further influenced by agitation contributions have been made to the literature about and changes in temperature during shipment. The latter changes in chemical composition taking place on aging. applies particularly to the samples received from California. Rocques (8) found that red wines aged 6 years were higher Although chemical analysis does not take the place of in esters and in higher alcohols than wines aged 1 year. organoleptic tests in judging the degree of aging of wines, Scurti and Corso (9) found that the total amount of esters some interesting observations were made, particularly with increases during aging. regard to the gradual increase in volatile esters in most cases. Trillat (11)stated that if wine is agitated or simply exposed I n some cases the first samples came in before the fermentato the air, aldehyde formation takes place slowly but always tion was quite complete so that all the first samples were held more rapidly than in solutions of alcohol of the same strength. in the 0’ F. (-17.8’ C.) room until the analyses were started, Laborde (6) stated that yeasts and anaerobic organisms and in one case the first sample was fortified in order to secrete reductases which may contribute to the complete stabilize it until analyses could be completed. removal of aldehyde from wine kept free from air but which Holding the wine a t low temperature caused the precipitaare unable to act appreciably on aldehyde combined with tion of some of the tartrates, which results in lower figures for sulfurous acid. total and combined tartaric acid, extract, and ash in samples Bottini (1) examined seven naturally aged Barbera wines thus treated. produced by the same vinification process from the same Analyses were made as complete as possible, including source and differing only in the year of production (1903alcohol, extract, ash, tartaric acid (total, free, and com1922). Analysis showed that the alcohol content increased bined) , total acidity, volatile acids, volatile esters, aldehydes, with aging due to loss of water. The extract did not suffer color and tannin, and pH. The methods of the Association of appreciable variation. The volatile acidity did not change Official Agricultural Chemists were used. The tables give the sensibly since the acetic acid formed in aging is almost comresults of analysis. pletely esterified. Esters were almost entirely absent from the young wines, and those of the old wines were mostly volatile. Seiler (IO) studied the changes taking place during Oxidation-Reduction Potential the storage of bottled wines. I n most cases he found a Some time was given to an attempt to make oxidationdecrease in alcohol and in nonvolatile acidity. There was no reduction (“Redox”) potential measurements on wines to see appreciable change in specific gravity, extract, sugar, volatile whether any Redox system or systems could be detected or acidity, and tartaric acid. Joslyn (6) found an increase in esters on aging wines, a slight increase in acetaldehyde, acetal, and volatile acids, and a decrease in tannin, color, OF IVES WINE FROM NEWYORK TABLE I. RESULTSOF PERIODIC ANALYSES and total acidity. WINERYA Changes during aging of distilled liquors were Date of receipt of sample 11/22/35 4/8/36 6/22/36 9/26/36 12/23/36 6/2/37 12/21/37 studied by Crampton and Tolman (8) and by Age, days 137 212 308 396 526 728 Alcohol, % by vol. 11.31 11.38 11.16 11.3 11.1 10.94 10.72 Valaer and Frazier ( l a ) . Garino-Canina (S), Extract, grams/100 cc. 2.36 2.60 2.40 2.49 2.32 2.27 2.30 Ash, arams/100 cc. 0.119 0.153 0.145 0.152 0.138 0.144 0.140 Geloso (4), and Riberau-Gayon (7) studied the Alkalrnity .of ash, cc. relation of the oxidation-reduction potential to 0.1 N HCl: Water-sol. ash 4.8 10.0 9.1 9.6 8.0 8.2 7.9 the aging of wine. Water-insol. ash 6.8 11.3 10.4 11.8 11.0 12.2 11.6
T
Chemical Analyses This study was undertaken for the purpose of following by chemical analysis the changes taking place during the aging of wines in vats. Material for the work was supplied by two wineries in New York State and one in California; each winery submitted a sample of red and a sample of white wine every 3 months during the first year, and after 6-month periods, during the second year of aging.
Grams per 100 cc.: Total acids (as tartaric) 0.862 Total tartaric acid 0.451 Potassium acid tart.rate 0.090 Free tartaric acid 0.277 Tartaric acid combined with alkaline earths 0.102 Volatile acids (as acetic) 0.095 Volatile esters (as ethyl acetate) 0.026 Aldehyde 0.0005 Color and tannin 0.194 Reducing sugars 0.152 2.87 PH This sample was cold-treated in b Sulfured?
1279
0.918 0.514 0.188 0.196
0.908 0.466 0.171 0.203
0.918 0.492 0.180 0,171
0.905 0.475 0.150 0.190
0.843 0.453 0.154 0.147
0.956 0.456 0.149 0,164
0.169
0.156 0.077
0.177 0.097
0.165 0.100
0.183 0.115
0.174 0.165b
0.028 0.029 0.037 0.039 0.001 0.003 0.0015 0.009 0.216 0,260 0.216 0.226 0.152 0.154 0.216 0.122 2.93 2.95 2.95 2.88 the 0’ F. room after receipt.
0.032 0.009 0.205 0.129 2.97
0.048 0.001 0.196 0.155 2.94
0.088
INDUSTRIAL AND ENGINEERING CHEMISTRY
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VOL. 31. NO. 10
TABLE11. RESULTS OF PERIODIC ANALYSES OF DELAWARE WINEFROM NEW YORKWINERYA D a t e of receipt of sample
Age days Alcdhol % by vol. Extract: grams/100 00. Ash, grams/100 00. Alkalinity of ash, 00. 0.1 N HCl: Water-sol. ash Water-insol. ash Grams er 100 00.: Totaracids (as tartaric) Total tartario acid Potassium acid t a r t r a t e Free tartaric acid Tartaric acid combined with alkaline earths Volatile acids (as acetic) Volatile esters as ethyl acetate Aldehyde Color and tannin Reducing sugars PH 5
December 22 1935 4/8/36 As Cdldretreated ceived a t OD F. 137 11.99 11.9 2.03 1.83 1.97 0.158 0.092 0,129
....
9/26/36 12/23/36O
6/2/37a
12/21/37a
212 11.42 1.92 0.140
308 10.7 1.86 0,140
526 11.55 1.75 0.149
728 11.56 1.80 0.115
9.4 7.0
4.2 7.2
0.727 0,337 0.177 0,088
0.652 0.194 0.079 0.024
0.671 0.270 0.194 None
0.712 0.307 0.189 0.026
0.759 0.267 0.184 None
0.105
0.108 0.065
0.116 0.061
0.126 0.055
0.023 Trace 0.019 0.092 3.19
0.026 0.0025 0.032 0.093 3.17
0.026 0.0005 0.030 0.110 3.11
.... .... .... ..... ...
10.3 8.9
6/22/36
10.04 8.4
9.8 8.4
396 11.75 1.82 0,133 10.6 8.6
8.9 9.4
5.2 9.1
0.675 0.289 0.199 None
0.693 0.262 0.167 None
0.711 0.235 0.098 0.021
0.120 0.149b
0.129 0.075
0.129 0.078
0.137 0.126
0.034 Trace 0.026 0.171 3.14
0.037 0.0005 0.018 0.076 3.13
0.039 0.0005 0.017 0.091 3.22
0.048 0.0005 0.024 0.082 3.12
Not from the same vat as the previous samples.
b Sulfured (runs volatile acids up temporarily).
TABLE111. RESULTSO F PERIODIC ANALYSES OF CLINTON-IVES WINE5 FROM NEWYORKWINERYB 'Date of receipt of sample
November 1,1935 2/24/36 5/29/36 9/2/36 11/20/36 ColdAs treated reO o F.. ceived fortified 209 384 115 305 8.85 8.82 8.72 9.18 11.9b 8.3 2.93 2.88 2.81 3.00 3.24 2.81 0.250 0.214 0.252 0,209 0.253
Age days Alcdhol % by vol. Extract: grams/100 cc. Ash grams/100 00. A l k h n i t u of ash, cc. 0.1 N HCl: 12.5 13.6 9.3 10.5 17.5 Water--sol. ash 14.4 14.8 12.1 Water-insol. ash ... 7.4 14.8 Grams per 100 cc.: 1.125 1.087 1.28 1.095 1.185 1.181 Total acids (as tartaric) 0.506 0.506 0.488 Total tartariq acid 0.787 0.341 0.600 0.235 0.175 0.256 0.329 0.598 0.197 Potassium acid tartrate 0.102 0.081 0.166 0.072 0.115 None Free tartaric acid Tartaric acid combined with 0.222 0.181 0.216 0.216 0.111 0.222 alkaline earths 0.034 0.036 0.041 0.020 0.032 Volatile acids (as acetic) 0,009 0.008 0.011 Volatile esters (as ethyl acletate) o:oi5 0.015 0.010 0.0005 Trace None Trace Trace Aldehyde 0.259 0.250 0.236 0,272C 0.244 Color and tannin 0.272 0.245 0.286 . . . 0.267 0.290 2.96 Reducing sugars 2.96 2.9d 2.95 2.99 PH 5 A proximately 13% Clinton and 87% Ives. b Tge sample held for complete analysis was fortified. Winery stated that tannin was added a t this time t o clarify. d Experiments closed and wines blended. I .
...
...
... .,.
OF PERIODIC ANALYSES OF CATAWBA WIN^ FROM NEW TABLEIV. RESULTS YORKWINERY B
Date of receipt of sample
11/1/35 2/24/36 Coldtreated a t O o F. 115 8.53 8.7 2.48 2.44 0.152 0.127
5/29/36 9/2/36 11/20/36
system by titrating with dilute potassium ferricyanide or by passing in oxygen did not reveal any evidence of such a system at the natural pH of the wines. The unstable nature of the potentials observed were also in accord with the probable absence of any appreciable quantities of materials capable of forming a Redox system. A limiting potential of +0.058 volt (referred to normal hydrogen electrode) a t pH 3.18 was obtained by sealing a sample of wine in a glass tube into which a glass electrode and a platinum electrode were sealed to permit Redox measurements on the hermetically sealed tube. This corresponds to a slightly lower value than Geloso (4) reported. It is not felt that these limiting values are of great significance in view of the apparent absence of any detectable amount of a reversible Redox system a t the pH of the wine.
Discussion
When the wines were sulfured, a temporary increase was noted in the volatile acids, and 209 305 384 Age days 8.65 8.95 8.87 Alcdhol % by vol. when the cellar treatment included the addi2.44 2.52 2.45 Extract: grams/100 cc. tion of tannin for clarifying, an increase in the 0.163 0.164 0.163 Ash grams/100 00. Alkhinity of ash, cc. 0.1 N HCl: color and tannin content followed. 11.2 11.0 12.4 11.6 7.6 Water-sol. ash 11.4 12.6 10.8 10.9 7.5 Water-insol ash A reduction in sugar content resulted in Grams er 100 cc.: the California wines, but the sugar did not 1.459 1.470 1.601 1.560 1.545 Totafacids (as tartaric) 0.633 0,641 0.709 0.679 0.671 Total tartaric acid entirely disappear after 2 years in any case. 0,207 0.232 0.143 0.218 0.210 Potassium aoid tartrate 0.373 0.340 0.304 0.265 0.444 Free tartaric acid A few anomalous results were obtained on Tartaric acid combined with alk d i n e aldehydes. Notably, the aldehyde in the zin0.171 0.163 0.189 0.112 0.162 earths 0,041 0.034 0.033 0.034 0.030 Volatile acids (as acetic) fandel sample ran up to 0.005 gram per 100 0.006 0,009 0,009 0.010 0,008 Volatile esters (as ethyl acetate) Trace 0.0005 None 0.0005 Trace cc. after 6-month aging; the previous sample Aldehyde 0.033" 0,028 0.045 0.042 0.016 Color and tannin showed only
