UNIVERSITY OF CALIFORNIA Agricultural experimentStation 
 
 College of agriculture e. j. wickson, acting director 
 
 BERKELEY, CALIFORNIA 
 
 CIRCULAR No. 22 
 
 (August, 1906.) 
 
 DEFECATION OF MUST FOR WHITE WINE. 
 
 BY 
 
 FEEDEBIC T. BIOLETTI. 
 
 The manufacture of wine consists in a series of operations which 
 has for its objects : First, certain chemical changes, the chief of which 
 is the production of alcohol from the sugar, and, second, certain 
 physical changes, the chief of which is the clarification of the wine. 
 
 The clarification of the wine is accomplished by separating it from 
 all solid or undissolved particles. Some of these particles consist of 
 fragments of skin, pulp and seeds, dust, yeast and germs of various 
 kinds, introduced with the grapes. Others are due to physical and 
 chemical changes which take place during the manufacture, by which 
 substances dissolved in the must or young wine become insoluble in 
 the finished product. Such are the albuminoids and cream of tartar 
 which are precipitated by the aging of the wine. Finally, there are 
 the cells of yeasts, molds and bacteria which grow in the wine during 
 and after fermentation. 
 
 All these impurities must be separated from the liquid by settling 
 and decantation, or by straining and nitration, and the w r ine is not 
 marketable until they have all been eliminated. 
 
 In the case of red wine a large part of this separation takes place 
 in the fermenting \^at. The tannin of the skins and seeds diffuses into 
 the must and coagulates the albuminoids which, together with much 
 other solid matter, are removed from the wine by the filtering action 
 of the pomace. The utility of this early partial clearing of the wine 
 is seen in the superior quality of the ' ' free run, ' ' in which the filtering 
 action is considerable, over the ' ' press wine ' ' where it is less. 
 
In the case of white wines the tannin is insufficient to precipitate 
 the albuminoids and the filtering action of the fresh grapes is very 
 slight. For these reasons, the clearing of white wines is always much 
 slower than that of red and the sediment more bulky. Many of the 
 troubles of white wine can be avoided and the quality improved if 
 the must is given a preliminary clearing or "defecation" before 
 fermentation. The wine will clear more rapidly, and will be less liable 
 to secondary fermentations, and will be, in general, sounder and 
 cleaner tasting. It also makes the use of pure yeast more effective. 
 
 Some of the impurities can be kept out of the must by careful 
 handling of the grapes or by hand sorting before crushing. These 
 methods, however, are expensive and at best very incomplete. If the 
 grapes are stemmed, a certain quantity of leaves, dried and rotten 
 grapes and particles of soil are thrown out, but the proportion is not 
 large and the absence of the stems increases the difficulty of pressing. 
 
 If great care and cleanliness are exercised in gathering, crushing 
 and pressing and the grapes are only handled when cold, the must 
 will free itself of most of its impurities during the first 24 hours by 
 settling. If the must is warm, however, or contains a large amount 
 of yeast taken from boxes, crushers or conveyers, fermentation will 
 start before the impurities have time to settle. During fermentation 
 the continual escape of carbonic acid gas will keep all the solid parti- 
 cles in suspension and any of them which are capable of injuring the 
 quality of the wine will have abundant time to do so. Some means 
 of preventing all fermentation for 24 or 48 hours is necessary if the 
 impurities are to be separated before fermentation. 
 
 Such a means we have in the use of sulphurous acid.* Sulphurous 
 acid may be obtained in the liquid state in iron bottles, dissolved in 
 alcohol, or in the form of potash salts (potassium meta-bisulphite), 
 but the cheapest and most convenient source for the purpose of 
 defecating white must is sulphur. If sulphur is burned, it is changed 
 into a gas, which is pure sulphurous acid. 
 
 The most convenient way of using the fumes of burning sulphur 
 for clearing the must is to have two or three defecating vats or casks. 
 These vats should be headed up and of such size that one of them is 
 filled in a day. The proper quantity of sulphur is burned in the 
 cask immediately before introducing the must. The amount necessary 
 will vary according to the temperature and the condition of the grapes, 
 but will lie between .1 and .2 per mille. That is, for a puncheon of 
 
 * For a fuller discussion of the use of sulphurous acid in wine-making see Bull. 
 167, pp. 45-51. 
 
175 gallons 2 to 4 ounces of sulphur will be needed, or for a larger 
 vat about one pound of sulphur for every 1000 gallons. 
 
 In order that this amount of sulphur shall be sufficient, some means 
 must be used to make the must absorb most of the fumes. This is 
 most easily done in small cellars by pumping the must through a 
 rose nozzle which projects Only a few inches into the cask. For larger 
 cellars where steam pumps are used the must may be forced to fall 
 in a spray by means of a piece of board about 1 foot square suspended 
 in the defecating vat 15 inches below the nozzle through which the 
 must enters. The exact amount of sulphur to use under the conditions 
 of any particular cellar can be determined only by trial. If the must 
 commences to ferment before it clears, more sulphur should be used. 
 If it remains several days without fermenting after yeast has been 
 added, less should be used. If too much is used no harm is done except 
 that time is lost. 
 
 The usual way of burning sulphur in a cask is to use sulphur 
 matches or tapes, which are strips of thin cotton cloth which have 
 been dipped several times in melted sulphur. These tapes are hung on 
 an iron wire about 18 inches long, bent up at one end to hold the 
 tape and fastened to a bung at the other. This method has the defect 
 that some of the sulphur melts and drips on to the bottom of the vat, 
 where it is incompletely burned. This incompletely burned sulphur 
 may communicate a bad taste to the wine. The same is true of the 
 burning of the cloth to which the sulphur is attached. A better method 
 is to use thin paper instead of cloth for the tapes and to burn them 
 in a sulphur cage. A sulphur cage is simply a hollow cylinder of 
 iron, or better, of porcelain, open on top and closed below, sufficiently 
 narrow to enter the bung hole and sufficiently long to hold the required 
 amount of sulphur tape. The cylinder is pierced with numerous holes 
 in all parts except the bottom inch, which acts as a cup to catch all 
 the melted sulphur. The cylinder is suspended at 18 inches below 
 the head of the vat by means of a piece of iron wire attached to a bung. 
 
 The defecating vat may be filled completely, and the must should 
 be allowed to settle for at least 24 hours and not more than 48. At 
 the end of this time it should have deposited most of its impurities. It 
 is then drawn off into the casks or vats in which it is to ferment. 
 
 In drawing off, the defecated must should be thoroughly aerated. 
 This is accomplished by allowing it to fall as a spray into the pump 
 well and in the same manner from the top of the cask into which it 
 is pumped. This aeration rids the must of some of its sulphurous 
 acid and supplies the oxygen necessary for the development of the 
 
yeast. The must will ferment without the addition of yeast, for defeca- 
 tion practised as described never completely frees the must from all 
 yeast cells. It may, however, be a long time in starting and it is better 
 to use a starter. 
 
 This starter may be simply some must from a cask which is already 
 in full fermentation. Full fermentation may be considered to be when 
 from one-third to one-half of the sugar has disappeared. For exam- 
 ple, must which contains originally 24% Balling may be considered in 
 full fermentation when the saccharometer shows between 16% and 
 12% B. Ten gallons of such a starter is sufficient for 1000 gallons 
 of defecated must. 
 
 Care, of course, should be taken to use starters only from the 
 casks or vats which have been filled with the best grapes. The most 
 satisfactory starter is that prepared from pure yeast in the manner 
 described in Circular No. 23. 
 
 Summary. 
 
 The defecation of must with sulphur fumes for the production of 
 white wine is desirable because : 
 
 1. It eliminates the worst of the impurities before they have 
 contaminated the wine. 
 
 2. It diminishes the amount of sediment in the casks at the first 
 racking. 
 
 3. It causes the wine to clear much more rapidly after fermenta- 
 tion. 
 
 4. It eliminates much of the albuminoid substances which are the 
 preferred food of injurious bacteria. 
 
 5. It clears the wine of most of the molds, wild yeasts and bacteria. 
 
 6. It enables us to use pure yeast with the greatest effect.