REPORT OP COMMITTEE ON PUBLICATION 309 



The concensus of opinion seemed to be that in a general way the riper 

 the grapes the higher the quality and the higher the ratio of dried grapes 

 to fresh. Whether this higher ratio represented an actual increase of dry 

 matter or final crop, or simply a partial drying on the vine, was not 

 discussed. 



During the following season, 1913, an attempt was made by the California 

 Agricultural Experiment Station to throw light on these doubtful points and, 

 specifically, to determine the changes in drying ratio, time of drying, quality 

 of raisins and quantity of crop with advancing maturity of the grapes. 



The plan adopted was to gather five trays (110 pounds) of grapes when 

 they reached about the minimum degree of ripeness at which it is ever 

 attempted to make raisins, and to dry them by the usual methods adopted in 

 the San Joaquin Valley. A similar amount was gathered thereafter every 

 seven days and dried in the same way, as long as the weather permitted. 

 These tests were carried out by Mr. A. E. Way at the Kearney Vineyard. 

 The variety was the ordinary raisin grape, Muscat of Alexandria. 



During the season of 1914 these tests were repeated at Kearney on a 

 larger scale and similar tests at the same place made with Sultanina. Both 

 varieties were tested in the same way also at Davis by Mr. F. Flossfeder. 



1. Time of Drying. As the season progresses the days become cooler 

 and the nights longer and as a consequence the time necessary for drying 

 increases, as is shown by the following record. 



Table I Muscat, Kearney, 1913. 



Date Drying Time in Days Date 



Bal. Gathered Turned Stacked Boxed Finished 



1 21.00 Aug. 17 6 13 Aug. 30 



2 23.90 Aug. 23 6 .... 15 Sept. 7 



3 25.50 Aug. 30 9 .... 17 Sept. 16 



4 26.75 Sept. 8 8 16 21 Sept. 29 



5 28.75 Sept. 16 13 23 34 Oct. 22 



The process of drying required only about two weeks early in the season, 

 but nearly five for the last picking in the middle of September. The drying 

 of the last two pickings took place principally in the "stack," that is after the 

 raisin trays had been placed one on top of another in piles of about ten trays. 

 This, together with the cooler and shorter days, accounts for the greater time. 

 Slow drying is favorable to quality as is also drying in the shade, such as 

 occurs in the stack. 



2. Drying Ratio. The number of pounds of fresh grapes required to 

 make a pound of raisins is called the drying ratio. Estimates of the value 

 of this ratio by various growers vary from 4.25 to 3.5. It depends on a num- 

 ber of factors. As the change of grapes into raisins consists essentially and 

 principally in the evaporation of a large portion of the water, the chief factor 

 is the degree of maturity of the grapes. The riper the grapes the more solid 

 material they will contain and the less weight they will lose in drying. It is 

 influenced also by the variety of grape, the compactness of the bunches, the 

 percentage of stems and by the amount of loss in gathering, turning, boxing 

 and hauling. 



