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 ) 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-.nfi.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- °%er!uh>>j, DccrjQ. lSS:. E. VT. Hilcakd.