412 Bulletin 167 



comparison oe sirups made from inoculated sap and from 



natural sour sap 



The reader with a practical turn of mind may well inquire 

 how the quality of the sirups made from the inoculated saps 

 compares with that of the sirups made from saps which have be- 

 come sour from natural causes. It might seem that the artificial 

 introduction of large numbers of bacteria into sap would result in 

 the production of an abnormal sirup, far inferior to that secured 

 from saps souring under natural, and perhaps unavoidable, con- 

 ditions ; but such is not the fact. Much sirup and sugar are 

 annually made from sap more seriously injured by natural 

 souring than was most of that discussed in the foregoing 

 pages. The organisms at work are the same in either case, 

 but the conditions under which souring occurs in nature are 

 as a rule more favorable to bacterial growth than were those 

 maintained in the incubator. In nature, however, there is al- 

 most always a mixed infection, in which the predominant forms 

 are those most seriously injurying the color. In the incu- 

 bator it was possible so to control conditions as to give the 

 advantage to particular groups at will, so that in some cases the 

 flavor of the sirup was more seriously injured than is likely to 

 occur in nature unless the conditions are extremely bad. The 

 writer, while unwilling to acknowledge himself a great offender, 

 has personally made sirups for commercial sale from saps in- 

 jured more seriously by natural souring than were most of those 

 employed in these experiments. In fact only the most pains- 

 taking care can prevent the occurrence of such injury towards 

 the close of the season. 



The facts are brought out clearly by a study of the data 

 already presented. Twelve of the sirups discussed were made 

 from sap which had soured naturally. The average color was 

 8.3, flavor 4.3, and score 381 ; average depreciation from first run 

 control, color 9.2, flavor 2.6, and score 504. Three of these 

 samples, however, (Nos. 84. 85 and 86) were made from sour sap 

 which had been allowed to stand two or three days in the buckets 

 so that it was very poor indeed: and six (Nos. 88, 121, 123, 125. 



