UNIVERSITY OF CALIFORNIA. 
 
 AGRICULTURAL EXPERIMENT STATION. 
 
 BULLETIN NO. 7 7. 
 
 The Extraction of Color and Tannin 
 during Red-Wine Fermentation. 
 
 The observations of wine colors made last 
 season in connection with the experimental fer- 
 mentations at the Viticultural Laboratory, 
 showed unexpectedly great differences in the 
 behavior of the wines from different grapes dur- 
 ing the period following fermentation. It was 
 found that some grapes while yielding a very 
 deep color at pressing would lose it rapidly 
 afterward, and frequently fall below others that 
 at pressing had shown materially less color. It 
 was also shown by comparative experiments in 
 fermentation of the game grape under different 
 conditions, that not only the initial intensity of 
 color ($. e., at pressing) varied materially, 
 but also that the rate of loss was different, and 
 that apparent advantages gained (e. g. t by hot 
 fermentation) in securing intensity of color do 
 not hold out, and that in certain cases an actual 
 inversion of the proportion at first existing be- 
 tween different samples derived from the same 
 grape may take place. It was further shown 
 that with the deposition of color the tints of 
 wines change from the purplish-reds toward 
 red, and from the reds toward orange-red. 
 
 Considering the importarce at present attach- 
 ed, commercially, to depth of tint, it was deter- 
 mined to study more closely, this season, the ex- 
 actcourseof thedevelot. mentof colorin the wines 
 formed under different methods of fermenta- 
 tion, in order to determine the conditions that 
 would secure the greatest depth of tint from 
 the same grape, not only at first but perma 
 nenlly. While the question of permanency 
 
 f 
 
 o\. 22, 1887 
 
 Dec. 12,1887; 
 
 Total 
 De- 
 crease 
 P'r ct. 
 
 nt. Tint. 
 
 Int. 
 
 Tint. 
 
 2.5 1 r. 
 2.0 1 r. 
 5.4 (-2 v. r. 
 ) . 7 4 v. r. 
 i.O 12 v. r. 
 LA) 2 v. r. 
 1.4 1-2 v. r. 
 1.3 5 v. r. 
 {..> 4 v. r. 
 L8 6 v. r. 
 M 2 v. r. 
 
 35.3 1 r. 
 20.0 r. 
 
 45.4 2 v. r. 
 
 25.5 4 v. r. 
 
 31.6 J v. r. 
 
 26.2 2 v. r. 
 3S.0 1 v. r. 
 383 4 v. r. 
 
 31.3 2 v. r. 
 23.5 4-5 v. r. 
 38.0 1-1 v. r 
 
 54 . 2 
 
 72.6 • 
 
 35.0 
 
 40.0 
 
 48.0 
 
 52.4 
 
 33.5 
 
 54 . 4 
 
 45.0 
 
 53.0 
 
 45.8 
 
 of {Tes- 
 tation, 
 "ours. 
 
 Dec. 26, '87. 
 Per Cent. 
 
 Total 
 
 Decrease. 
 Per Cent. 
 
 S 
 
 34 8 2 v. r. 
 
 47.8 
 
 30.7, 1 
 
 -2 v. 
 
 r. 
 
 45 
 
 0 
 
 cannot, of course, as yet be decided with re- 
 spect to the present season's wines, the results 
 already obtained are of sufficient interest to 
 render a preliminary statement desirable. It 
 I is not intended to discuss at present other 
 1 points elicited, that require a longer time for 
 ! their full demonstration. 
 
 Aa it is usually supposed that the extraction 
 of color and tannin go together and continue to 
 the limits of the ordinary periods of drawing- 
 j off, no special arrangement for the control of 
 ■ the progress of tannin extraction was made in 
 the first series of fermentations. But after 
 these had shown conclusively that the above sup- 
 position is incorrect, another set of two was car- 
 ried through with the very last grapes available 
 for the season, *viz., a lot of third-crop Zn- 
 fande) courteously sent by Mr. John Galle- 
 gos. The material for the first series, amount- 
 ing to some 2500 pounds of excellent Carignane 
 (sugar 25.75, acid .53), was donated for the 
 purpose by Mr. A. Sabzar, Jr., of Mission San 
 Jose. The upper part of the table below refers 
 to this last-named lot, the lower to the Zin- 
 fandel; (sugar 21, acid .00.) 
 
 The conditions established for the several fer- 
 mentations were as follows: 
 
 The bulk (eight) of the first series of fer- 
 mentations was carried out at the air tempera- 
 ture of 75°, which may be considered as 
 practically the most desirable for most pur- 
 poses. The charge was 200 pounds for each 
 tank. Four of the tanks were provided with 
 b rated frames («* false bottoms ") to hold the 
 pomace submerged; one having three of these 
 (Perret's process)"so as to divide the pomace 
 i^tD three equal portions; another having the 
 oratin > i i ■ ced half wav down, so as tn hold all 
 
the pomace near the bottom of the tank. The 
 
 two others had the grating placed near the top! 
 of the ma8h, as is usually done; but in one the 
 wine was pumped over from below and 
 sprayed over the top twice daily, in lieu 
 of any other mode of stirring or aeration; while 
 the other (788) was left to complete its fermen- 
 tation without any kind of agitation. Of the 
 other four tanks, one (794) was charged with 
 unstemmed grapes, to be gradually crushed by 
 daily stirring ("Morel " process); another (792) 
 was left open and stirred twice daily with a 
 cross-peg stirrer; the third (793) was similarly 
 left open, but was stirred by pumping air to the 
 bottom; while the fourth (787) was treated ac- 
 cording to the method adopted for general pur- 
 poses in the laboratory, viz., a floating, solid 
 cover and twice-daily stirring. 
 
 One charge of 230 pounds (796) was fermented 
 according to the same method^ with an air 
 temperature of 62°. In this, as well as in the 
 eight preceding, the mash was set at 63°. 
 
 Two charges of 230 pounds each were fer- 
 mented with the air temperature kept at about 
 : 90°; the mash was set at 86°. One of these tanks 
 • (795) was provided with floating cover as above; 
 the other (797) was left uncovered and both re- 
 ceived twice-daily stirring. 
 
 The observations given in the table are 
 those made at 9 a. m. In the second series, two 
 tanks only were used, both with floating top 
 and stirring, as above; but one (799) with an 
 air-temperature of 75° and set at 63 a , the other 
 (S00) set at 86° and kept in a warm chamber 
 with air at about 90°; the charges in this case 
 were 60 pounds each; the observations were 
 made at short intervals in order to be sure of 
 not missing the maxima of color. — The latter 
 are printed in full-face type, for a readier view 
 of the facts. 
 
 The figures given in the columns headed 
 4 Intensity " refer to the scale in which a disc of 
 w;n3 four-ttnths millimeter or about the sixty- 
 second part of an inch in thickness is equal in 
 intensity to the type discs of Chevreul's color 
 scale. 
 
 In the columns headed "Tint," r. means 
 red and v. r. violet-red, the figures referring to 
 the numbered tints of Chevreul's scale. 
 
 No. 788 attained only 55.5 per cent of the color 
 reached by No. 795 three dav« before. But 
 when, as in the case of No. 7S9, the pomace 
 was held down near to the bottom of the tank» 
 a maximum of 60.0 of the color scale was 
 reached within the same time. Where the 
 single frame was used near the surface, hut the 
 wine pump<d over from beneath {So. 790), 55.0 
 was reached, and that two days earlier; where 
 the three frames were us 6d (No. 791) 57.1 was 
 the color, the maximum being reached at the 
 same time as in the two former, viz : on the 
 sixth day. 
 
 Comparing the three tanks treated in the 
 same manner, but at different temperatures, to 
 wit, Nos. 796, 787 and 795, having a fbating 
 cover and stirring twice daily, it appeais that 
 the same maximum of 70 0 was reached within 
 the same time (rifth da> ) both with air-tempera- 
 tures of 62 and 75°; in the one kept in a cham- 
 ber at 90 J , the maximum of 77 0 was attained 
 on the morning of the third day. This marked 
 influence of high temperature upon the extras 
 tlon of color iB also shown in the second series 
 of the table, as well as in last year's. 
 
 Contrary to expectation, the "Morel pro- 
 cess," in which the frequent stirring and pro- 
 longed fermentation would lead one to expect a 
 deep color, comes next to the lowest, withonly 
 50.0 of color, reached on the sixth day. 
 
 It thuR appears that in all but one of these 
 cases (795) the maximum of color was attained 
 between the fourth and sixth days. After 
 reaching the maximum, whether the wine is 
 drawn or not, there immediately begins a de- 
 crease, which, on the whole, is the more rapid 
 the higher the intensity that has been reached. 
 But the percentage of decrease (see last column 
 of table) varies materially, according to the 
 method of fermentation employed, as will be 
 seen from the figures in the last column to the 
 ri^hfc. But what interests us most is the absolute 
 intensity remaininrj a fter the sa?ne lapse of time: 
 and in that respect the color readings last made 
 (Dec. 12, h) are very instructive, as they doubt- 
 less foreshadow the ultimate outcome more or 
 less accurately. It will be seen that the deep- 
 est tint (45.0) was at that time retained by the 
 wine made according to the mode (with floating 
 cover and twice-daily foulage) adopted in the 
 
 tr 1 f 1 / ■ II 1 f l-lfO 1 1 fj l-\/-»*<0 f ftX.J nn.A r. +■ T ,t 3 Ilia 4-.n<nrm«a< _ 
 
 796 and 791, the first also fermented with float- 
 ing cover but at 62°, the second, according to 
 Ferret's method, with three frames. No. 195, 
 
 The last column to the right shows the per- 
 centage of decrease, referred to the deepest viticultural laboratory, and at 75 air temper- 
 tint observed, taken as 100. iteZllFSzPlk « ! Xt , hl ^ h6 ^ i 3 ^.*? Jt*£ 
 
 A glance at the full-face figures shows at 
 once the very great differences in the greatest 
 intensity of color attained in these experi- 
 ments, under the varying conditions. The fermented with floating cover but at 90 J , and at 
 maximum, 77.0, was reached on the third nrst showing the deepest tint of all, comes 
 day by No. 795, one of the two hot fermenta- ? ext below (35.3) having lost 54.2 per cent of 
 tions, being the one that reached the maximum lts color - - Nos - "92 and 793, both greatly ex- 
 temperature of 106°. The minimum, 42.5, is P 08ed to air during fermentation, stand re- 
 shown by tank No. 7SS, fermented according to 8 P e ctively 12 and 14 points below No. 787, fer- 
 one of the moet usual methods of procedure, ™ented with cover on; and the same influence 
 viz j A single grated frame keeping the pomace of f xc ess of air in diminishing colors is even more 
 submerged just below the surface. That is, 8 *"kingly shown on comparing Nos. 795 and 
 
797, both fermented at the high temperature 
 but one with cover on, the other open; the color 
 ratio being 35.3 to 20.0. 
 
 Omitting for the present the discussion ot 
 the causes of these differences, the broad fact 
 remains that in all cases the maximum of color 
 was reached, and its diminution begaD, long 
 before the fermentation was completed; that 
 therefore tho increase of alcohol beyond a cer- 
 tain point which from actual measurement in 
 one case was only five per cent has no influ- 
 ■ ence in promoting extraction of color. Also, 
 that the long-continued maceration sometimes 
 practiced with the idea that it increases thi 
 ! color, is erroneous. , 
 | In the second series of the table asm the 
 first, the hot fermentation completed the ex- 
 traction of color (12 hours) sooner than the 
 cooler one; and it is interesting to note the 
 I rapid course of these fermentations, as com- 
 I pared with the long-drawn-out process in th. 
 , Oarignane series, due, of course, to the ditt.r- 
 ' ence in the sugar and acid contents. Tne high 
 ten^ rushed the fermenta- 
 
 I tLn ri.htthrcugh, but the maximum reached 
 1 was only 08 5° against 106° in the former case. 
 ! Here alio he color was at first much deeper in 
 
 the hot than in the cold fermentation (l>fi.6 
 against 55.S), but the decrease was also more 
 rapid, as is shown in the later observations. 
 
 Bat during the whole time there was a steady 
 increase in the tannin contents, ending with .20 
 per cent for the hot and .144 for the cooler fer- 
 mentation. As it is proved that in sound wine 
 there ia no subsequent diminution of tannin, 
 this shows that longer time on the porhaca 
 steadily increases the tannin, as has bean sup- 
 posed; also, that hot fermentation materially 
 favcra the extraction of tannin. 
 
 The practical precepts following from these 
 experiments may then be thus stated: 
 
 1. Maceration of the wine on the pomace 
 after fermentation is through, increases tannin, 
 but adds nothing to color. • 
 
 o When blends are to be made for the sake 
 of color, or when blends of white and red 
 vines are to be made, it should, whenever 
 possible, be done before fermentation m order 
 that the white juice may help to hold up the 
 color that otherwise will come down very 
 rapidly during the first weeks after drawing- 
 
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