Keeping Quality o f Bottled Wines EFFECT OF HEAD SPACE which some of the contents had EDIMENTATION and C. S. PEDERSON been removed. color changes in wines have New York State Agricultural Experiment To simulate ordinary wine always been of great imcellar storage, the upper and Station, Geneva, N.Y. portance to wine makers. The lower ranges to be expected in warehouse or retail room-temsignificance of such changes is H. E. GORESLINE, A. L. CURL, perature storage and conditions somewhat doubtful, but the dethat might be expected in retail AND E. A. BEAVENS position of sediment or the shelf storage or in window dischange of color from the normal Bureau of Agricultural Chemistry and Engineering, play, the bottled wines were stored under the following concondition is usually not conU. S. Deoartment of Aariculture, Washington, D. C. ditions: One lot a t 60" F. sidered desirable. The action (15.6' C.), a second a t 70" F. of oxygen and light upon wine (21.1' C.), a third a t 85' F. was studied by Berthelot (9) (29.4" C.), and the fourth in sunlight a t room temperature. and by Pasteur ( 5 ) ; the latter showed definite decolorization of red wine and darkening of light-colored wine. The Methods of Examination deposition of small amounts of sediment in wines has been Observations were made on these samples in storage a t weekly investigated on numerous occasions, and explanations such intervals for the first month, and then a t monthly intervals up to as metallic contamination or growth of microorganisms 6 months. A t the end of this time all samples were stored in the have been offered for its formation. Joslyn (8, 4) reported dark a t 60" F. until analyses could be made. that wines heated in bottles with considerable head space During the storage period the samples were observed for visual changes in the color, clarity, and sedimentation and for spoilshowed aging effects while those with no head space remained age. A t the termination of the storage period the bottles were practically unchanged, and t h a t the oxidation produced an opened and examined for changes in color by the Lovibond increase in the aldehyde content of the wines. H e also colorimeter and a Fisher-type electrophotometer. The Lovibond showed that bottled sherry formed a precipitate in both filled colorimeter is a visual instrument in which the red, yellow, blue, and neutral colors of the sample may be matched against known and partly filled bottles, although more rapidly in the latter. intensities of these colors. The readings are made directly from I n view of the recent findings of Tressler and Pederson (6),in the instrument and recorded in terms of Lovibond color units. which the effect of air and sunlight upon grape juice was The electrophotometer is a colorimeter which makes w e of a studied, it was believed t h a t a study of wines would show photoelectric cell to record the degree of transmission (or absorpchanges similar t o those observed in grape juice. It was also tion) of light by a solution placed in an optical cell and interposed between the light source and the photoelectric cell. Red, green, thought desirable t o study the effect of storage temperature and blue-purple (called "blue" in this paper) filters are also intera s well as the effect of sunlight on the keeping quality of posed between the sample and the photoelectric cell, and the abbottled wines. sorption of light in these portions of the spectrum is recorded from a scale calibrated from 0 (no absorption) to 100 (complete absorption). Preparation of Samples Since turbidity markedly affects the transmission of light through solutions, it was necessary to filter out the precipitates Port, Burgundy, Tokay, and sauterne wines were chosen as caused bv the oxidation of the wine during storage. This was representing red and white varieties of high and low alcoholic condone by suction through Seita germ-proof sLeets, and since some tent. They were blended wines which were ready for bottling color was absorbed by the filter disk, all samples were filtered, reand were obtained in bulk from commercial wineries in the eastern gardless of their turbidity, in order to maintain uniformity of United States. They were filtered and filled as specified below treatment. It was determined that the passage of approximately into wine bottles of approximately 400-cc. capacity; the bottles 75 cc. of solution was necessary t o saturate the small 60-mm. filter were closed with high-grade wine corks and stored as specified. disks with color; therefore 75 cc. of each sample were filtered beThe wine was filled into the bottles in the following manner: fore the sample for analysis was taken. One lot of each fortified wine was filled into the bottles a t room Those samples which had not already undergone oxidation temperature (85' F. or 29.4" C.), corked, and stored without furbecame turbid in a short time by exposure to the air, and therether treatment; a second lot of each of all four wines was filled fore determinations had to be made soon after filtration. The into the bottles a t 130' F. (54.4" C.) and immediately corked; a entire optical svstem had to be cleaned frequently in order to third lot was filled into the bottles a t room temperature, corked, keep all values Eonstant. and then pasteurized for 20 minutes a t 130" F.; and a fourth lot For colorimetric tests a sample was carefully drawn from the was bottled after addition of 50 p. p. m. sulfur dioxide to see if this bottle by a siphon in order not to disturb any precipitate. The would stabilize the color. 100-cc. sample for examination, obtained after discarding the When the wine was heated in bulk, most of the occluded and first 75 cc. of filtrate, was divided; one portion was used in making dissolved ases were driven from the wine; and when the bottle the reading on the Lovibond instrument and the other portion, was filled full while hot, little air was left in the head space and a in the electrophotometer. partial vacuum was developed upon cooling. Where the wine The samples were also tasted for possible changes in flavor. was filled into the bottles cold, the dissolved, occluded, and headAnother set of samples was analyzed for changes in volatile space air had a chance to react with the wine durin storage. acidity, aldehydes, esters, tannin, and coloring matter according The head space in the bottles was varied in the fotowing manto standard methods (1). ner: FULLbottles were filled to a point where the cork would just Experimental Results touch the wine and thus eliminate as much head space as possible. After cooling, these averaged 3.4 cc. of head space. During storage a slow change occurred in some of the NORMAL bottles mere given a fill as close as possible to commercial practice. They averaged 16.3 cc. of head space. bottles. This was evidenced in the sauterne and Tokay THREE-QUARTER bottles had an exaggerated head space, wines by darkening, which was more pronounced in the latter. roughly averaging 97 cc. This was to demonstrate the effect of A slight precipitation in the sauterne was finally observed, large amounts of air on bottled products such as would be found but throughout the storage period no clouding effect was in slack-filled bottles or those which had been opened and from
S
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INDUSTRIAL AND ENGINEERING CHEMISTRY
noted even in the wines under the most adverse conditions (Table I). Figure 1 shows the darkening of the co!or and the relative amount of sedimentation a t the base. The changes in Burgundy and port wines held under adverse conditions were more marked; the wines first clouded and then changed in color from purplish red to muddy red and finally to brown, accompanied by a marked sedimentation. These changes were more pronounced in the port. Because of their very dark color they could not be photographed. Visual observations of color changes are only qualitative, and therefore determinations of the change in color were made by the Lovibond colorimeter and the Fisher-type electrophotometer. The Lovibond readings were taken in the red, yellow, and blue ranges (Table 11), using a dilution of 1 to 3 for port wine and 1 to 1 for Burgundy, since the depth of color of the wine was beyond the range of the instrument. I n general there was a decrease in the red and yellow readings for port wines as the amount of head space was increased and also a tendency to lose color as the temperature of storage was increased and most of all when stored in sunlight. I n the Burgundy wines the same decrease in the red range was noted but there was an increase or deepening of color in the yellow range as the head space was increased and the temperature of storage was increased. I n the Tokay and sauterne wines there was an increase of yellow color and a slight but variable increase in the red range as the head space and the temperature were increased. The color readings were lower in the latter because of the light color of the sauterne, but the proportional increase in color was greater. Lovibond readings are visual, and since to some extent the personal equation enters into the determination, the results were supplemented by the use of the photoelectric method. Readings were first taken without a filter, in order to get the transmission of light of all wave lengths through the sample; then readings were taken with red, green, and blue filters interposed. The values (Table 111) represent the transmission values of the undiluted wine. The values for "no filter" are the actual readings and indicate in the first set of figures that 81.8 per cent of the light is transmitted and 18.2
305
Changes in color, flavor, and clarity and the formation of sediment in bottled wines detract from their sale value. A study was made of the methods of filling, closing, pasteurizing (light wines), and storage, and their effects on the keeping quality of bottled products. Port, Burgundy, Tokay, and sauterne wines were studied. The bottled samples were stored in the dark a t 60", 70°, and 85" F. and in the sunlight a t room temperature. In the presence of large amounts of air, port and Burgundy wines showed a loss in red color, and a sediment was formed. There was an increase in volatile acidities and aldehydes and a decrease in color and tannin. The esters remained about the same. In sauterne and Tokay wines there was a browning of the color, cloudiness, increase in aldehydes, and a small decrease in color and tannin. The esters and volatile acidities showed little change. It was evident that the oxygen in the head space was responsible for most of the changes, and that by the elimination of air from the wine and head space of the bottled product the changes could be held to a minimum. This was accomplished by completely filling the bottles with hot wine, immediately closing, and thus producing a vacuum upon cooling. Under these conditions little deterioration took place in the bottled wines during storage.
per cent absorbed. The red, blue, and green values are apparent body-color readings and are found by dividing the transmission readings by 3. The sum of the three subtracted from 100 represents the "black value". For example, the apparent body-color values for the Tokay sample full a t 60" F. are 30.5 per cent red, 25.6 blue, 19.3 green, and the black value (or color absorption) is 24.6 per cent. I n the port and Burgundy wines there was a decided tendency toward a decrease in absorbing power as the head space was increased (Table 111). This was true also when the temperature of storage was increased, while the greatest loss of color was shown when the wine was exposed to sunlight. There was an increase in transmission in the red and green ranges with increase in head space, while the blue values showed but little change. No explanation can be found for the fact that the 85' F. series showed less loss of color than that stored at 70' F. This was apparent to the eye as stated under visual observations. I n these experiments, as demonstrated by visual, Lovibond, and electrophotometer readings. sulfur dioxide did not have a stabilizing effect on the color of red wines. Normal Three fourths There was a slight darkenFull Normal Three fourths Full ing of the color, as evidenced Tokay Sauterne by a decrease in the transmission FIGURE 1. CHANGES OF TOKAY AND SAUTERNE AFTER STORAGE of light through the sample, d
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INDUSTRIAL AND ENGINEERING CHEMISTRY
TABLE I. EFFECT OF HEADSPACE AND
STORAGE
Stored a t 60' F. Full Normal a/d
Timeb
...
... ... ... ... ...
3 weeks 1 month 2 months 3 months 6 months
... ... ... ...
3 weeks 1 month 2 months 3 months 6 months
I . .
... ... ...
... ... ...
... ...
SD
SD
SD SD
... ...
... ... ... ... ...
... ...
..* ... ... ...
4 . .
SD
...
D
... ... ...
... ... ... C
...
...
HP HP
HP HP
SF
...
... ... ...
...
... ... *.. ... ...
SP
....
bD. SD
SD
... ... D D
D Sauterne Wine SD SD D D SD' D Port Wine
.... .... ....
.... .... .... c
c c
HP HP P HP P HP Burgundy Wine
.... .... ....
Vol. 33, No. 3 BOTTLESAT 130'
VISUAL CHANCES I N W I N E S FILLED INTO
Stored a t 70° F. Full Normal */d Tokay Wine
*..
. . ~ ... ... ...C
3 weeks 1 month 2 months 3 months 4 months 6 months
TEMPERATURE UPON
'
Stored a t 85' F. Full Normal
a/$
... ... ... ... ...
SD SD SD
SD D D D
bD'
SD
...
bD'
...
... ... ...
SD
SD D D
... ... ... ... ... ...
D
D
DP
.... .... ..... ...
c c
HP HP HP HP
P
P
SP
.... .... .... ....
F.O
Stored in Sunlight Full Normal a/d
... ...
SD
D
SD
D
SD SD
D D I3
D D
...
SD
SD
... ... ... ... ...
...C . e .
SD D D D
D D D DP
... ... c
...c
HP HP
... ..*
...
HP
c
HP
c
HP HP
HP
2 weeks ... sc SC 3 weeks ... ... SC c 1 month ... SC SC SC c 3 months sc HP HP sc HP 6 months sc iGP HP SCP HP HP HP a Results of visual examination of samples unpasteurized, filled cold and pasteurized, and treated with SO1 were so similar t o those in the tables that their presentation was believed unnecessary. b The times are those when the first visual changes were observed in the wine; a blank indicates no visible change; S = slight; H = heavy; C turbid or cloudy; P precipitate; D color change.
... ... ...
... ...
...
-
sa
... ... ...
... ... ...
-
-
OF HEADSPACE AND STORAGE TEMPERATURE O N THE COLOR OF WINES FILLED INTO BOTTLES AT 130' F. TABLE 11. EFFECT RECORDED BY A LOVIBOND COLORIMETER
Color4
Full
Stored a t 70° F. Stored a t 85' F. Stored in Sunlight Full Normal l/r Normal a/, Full Normal a/, Tokay Wine 1.7 1.1 1.7 1.7 1.2 1.1 1.6 1.1 1.6 1.1 3.4 2.1 3.1 3.3 2.2 2.1 3.0 2.1 2.4 2.1 Sauterne Wine 1.1 1.0 1.1 0.6 0.7 1.1 0.5 0.6 1.0 0.4 2.2 2.0 2.2 0.9 1.2 2.1 1.0 1.0 2.2 0.8 Port Wine, 1 t o 3 Dilution 6.0 5.9 5.5 4.6 5.9 5.5 4.4 5.9 6.0 4.5 5.7 5.5 5.7 5.0 5.8 6.4 4.5 5.6 4.8 5.0 Burgundy Wine, 1 t o 1 Dilution 10.5 16.0 15.0 9.1 13.1 13.0 8.7 13.3 13.3 4.1 9.2 7.7 6.7 8.3 6.4 6.2 7.3 5.5 6.3 5.3 all conditions were 0 for the sauterne and Tokay wines and constant a t 0.1 for port and Burgundy.
Stored a t BO0 F. Normal
Red Yellow
2.0 3.4
3.4
Red Yellow
0.5 0.8
0.7 1.1
Red Yellow
6.6 5.3
6.0 5.1
1.7
Red 15.9 16.0 Yellow 5.3 5.0 a Blue results for all samples under
AS
Full
a/,
OF HEADSPACE AND STORAGE TEMPERATURE ON APPARENT BODYCOLOR OF TOKAY AND PORT WINESFILLED TABLE 111. EFFECT INTO BOTTLES AT 130' F. AS DETERMINED BY ELECTROPHOTOMETER
Color
Full
Stored a t 60' F. Normal a/,
81.8
No filter Red Blue Green Black value
30.5 25.6 19.3 24.6
82.0 30.9 25.9 19.8 23.4
81.0 30.2 25.3 19.2 25.3
No filter Red Blue Green Black value
5.0 5.9 4.0 1.0 89.1
6.0 6.5 4.4 1.2 87.9
8.0 7.6 4.2 1.3 86.9
Stored a t 70" F. Normal a/, Tokay Wine 87.5 79.5 77.5 31.3 30.3 29.6 28.3 24.8 24.3 18.6 23.8 19.4 16.6 25.5 27.5 Port Wine 8.2 12.0 7.5 10.8 7.6 8.3 4.8 4.7 4.7 1.3 1.3 2.2 86.2 85.7 82.3 Full
Full
Stored a t 85' F. Normal
84.0 30.6 26.6 21.3 21.5
87.0 30.7 26.3 21.4 21.6
80.0 29.8 25.1 19.1 26.0
83.8 30.7 26.3 22.0 21.0
80.9 30.4 25.3 20.4 23.9
81.1 30.1 25.5 20.4 24.0
6.2 6.6 4.5 1.2 87.6
7.2 7.3 4.5 1.3 86.8
11.4 10.0 4.5 2.0 83.4
7.4 7.5 4.8 1.3 86.4
8.5 8.2 4.8 1.4 85.5
14.8 11.8 4.8 2.7 80.6
8/4
Stored in Sunlight Normal
Full
a/,
OF HEADSPACE AND STORAGE TEMPERATURE ON THE VOLATILE ACIDITY,ALDEHYDES ESTERS, AND TANNIN AND TABLE IV. EFFECT COLORING MATTEROF PORT AND SAUTERNE WINESFILLED INTO BOTTLES AT 130d F.
0.084 0.0025 0.051
0.085 0.0020 0.051
0.097 0.0040 0.053
Stored a t 70' F. Normal ;/4 Port Wine 0.082 0.095 0.099 0.0037 0.0032 0.0050 0.057 0.056 0.055
0.133
0.154
0.127
0.164
0.060
Full Volatile acid Aldehydes Esters Tannin and coloring matter Volatile aoid Aldehydes Esters Tannin and coloring matter
0.066
Stored a t 60° F. Normal a/i
0.0010 0.033
0.0036 0.033
0.059 0.0050 0.033
0.050
0.044
0.040
Full
.... ,. ,.
.... ....
0.143 0.125 Sauterne Wine
.... .... ....
....
.... .... .... ....
Full
Stored a t 85O F. Normal
1/1
Full
Stored in Sunlight Normal
8/4
0.089 0.0020 0.052
0.095 0.0020 0.054
0.096 0.0045 0.052
0.090 0.0015 0.055
0.084 0.0030 0.056
0.091 0.0060 0.052
0.141
0,143
0.125
0.150
0.140
0.118
0.069 0.0010 0.035
0.066 0.0010 0.035
0.060 0.0060 0.032
0.073 Trace 0.039
0.070 0.0005 0.036
0.061 0.0075 0.040
0.045
0.042
0.032
0.050
0.042
0.045
,
March, 1941
e
t
INDUSTRIAL AND ENGINEERING CHEMISTRY
of sauterne and Tokay wines (Table 111) under the conditions of the experiment with increased head space and storage temperature, while the methods of treatment of the wine itself showed but little difference. The various wines were tasted, and in those cases where there had been a loss of color or the formation of a precipitate, there was a "brown" flavor and an impression of flatness. I n most cases the difference in flavor was not marked except where precipitation had taken place. In the white wines where the color had markedly darkened, there was an impression that the wine had been heated to a high temperature. The sprightly flavor of the sauterne was lacking in those bottles with a large head space. Chemical determinations were made on all wines in an attempt to place the flavor impressions on a quantitative basis and to detect the effects of oxidation. I n general (Table IV) the port wines showed a slight increase in volatile acidity and a more marked increase of aldehydes as the head space was increased, and a general loss in tannin and coloring matter. (This is a chemical determination of combined tannin and color and should not be confused with visual color.) The esters showed but little change. Results upon Burgundy wine were similar to those obtained on port. I n nearly all cases the changes between the full and normal fills were slight, but were more pronounced as the head space was markedly increased. The temperature or condition of storage or the manner of treatment of the wine seemed to exert but little effect as far as these determinations were concerned. I n both white wines there was an increase in aldehydes as the head space was increased, and a loss in tannin and coloring matter. The volatile acidity of the sauterne showed a slight decrease as the head space was increased (Table IV). Tokay showed very little change. In both wines the esters remained constant regardless of head space, storage temperature, or wine treatment, although storage in sunlight did produce a slight increase.
Factors in Deterioration METHOD OF PRESERVATION. The changes occurring in the various series according to method of preservation were of little significance, The wine in those bottles filled full a t 130" F., those filled full without pasteurization, and those filled with wine preserved with sulfur dioxide showed only slight changes, regardless of method of preservation. The most marked change was in the port after 6-month storage. On the other hand, the wines filled normally into bottlesthat is, with about an inch or so of head space-showed, under adverse conditions, progressive changes beginning a t the end of the first month. These changes had little to do with the method of preservation, although it seemed that the changes in the sauterne were slightly more rapid in the bottles filled at 130 F. than those filled cold and pasteurized in the bottle. This difference was not apparent in the other types of wines. STORAGE CONDITIONS. Next to the amount of head space, the condition of storage was the most important factor in deterioration. The greatest change occurred in those bottles stored in the sunlight a t room temperature. With the exception of the port wine (Table I), the changes were progressively lessened with storage in the dark a t the three temperatures--85", 70°, and 60' F. For some reason, changes in the port were apparently less in those samples stored a t 85" F. than in those stored a t 70" and 60°, respectively. This held true not only for the wines pasteurized and fUed a t 130' F. but also for those pasteurized in the bottle, those preserved with sulfur dioxide, and those unpasteurized. AMOUNTOF HEAD SPACE. The amount of head space left in the bottle was apparently the greatest single factor in O
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307
causing changes. Little if any change could be noted in the sauterne, Burgundy, or Tokay wines filled into bottles with little or no head space, even when exposed to sunlight. Some change was seen in the port after 6 months, but the change was marked only in those bottles exposed to sunlight. Changes of color or turbidity were apparent in wines in bottles with the normal head apace, and they were particularly marked in those stored under the more adverse conditions. I n bottles filled three fourths full, changes were very marked and were observed in some containers as early as 2 weeks after bottling. In the Burgundy and port wines a heavy deposit formed, and the color was very poor. SUMMARY OF FACTORS. From visual observations of changes in the Wines, it is obvious that the best method of pasteurizing wines is to fill the bottles full a t the pasteurizing temperature, 130" F., since this method eliminates most of the air from the wine and decreases the amount of head space in the bottle. The temperature and condition of storage also appear to be important factors in the keeping quality of wines.
Summary Under the conditions of these experiments on eastern American wines, there was a general change in character in the bottled wines as the amount of head space of the bottle was increased. I n red wines this increase of head space caused a loss of color and the formation of a precipitate; in white wines it caused a darkening in color. There was a correlation between visual Lovibond readings and electrophotometer light-transmission readings. This was also shown by the tannin and coloring matter determination. There was a loss in color in the red wines and darkening of white wines as the temperature of storage was increased. The greatest change was exhibited when the wine was stored in sunlight. I n general, there was an increase in the volatile acidity and aldehydes of red wines as the head space was increased, while the esters remained unchanged. In sauterne wine there was a slight decrease in volatile acidity with increased head space, while in Tokay there was a slight increase. Both showed some increase with increased storage temperature. I n both white wines there was an increase in aldehydes, while the esters showed no appreciable change. The value of sulfur dioxide as a color stabilizer was not demonstrated in these tests. I n general, the manner of bottling or treating the wines had but little effect on their keeping quality as long as bottles were well filled. Filling the bottles hot brought about an elimination of the head space in the bottle and aided in keeping the effects of oxidation to a minimum.
Acknowledgment The authors acknowledge the assistance of D. K. Tressler in planning these studies, and the assistance of E. K. Nelson and E. N. Davis in certain analytical phases of these studies. Literature Cited (1) Assoc. of Offioial Agr. Chem., Tentative Methoda of Analysis,
4th ed. (1936).
(2) Berthelot, M., Compt. rend., 57, 796-7, 983-5 (1863); 58, 80-1,
292-6 (1864). (3) Joslyn, M.A.,Fruit Products J.,15, No. 1, 10-12 (1936). (4)Joslyn, M. A., IND.ENG.CnmM., 30, 568-72,(1938). (6) Pasteur, Louis, "Etudes sur le vin", 1st ed., Paris, 1866. (6) Tressler, D. K., and Pederson, C. S., Food Research, 1, 87-97 (1935). APPBOVXID by t h e Director of the New York State Agricultural Experiment Station for publication as Journal Paper 394. Contribution 509 from the Food Researoh Unit, Agricultural Chemical Researoh Division.
