416 Bulletin 167 



in a multiple pan evaporator in which the sirup was always drawn 

 off from the rear pan. Of course the usual accumulation of the 

 so-called niter (mainly malate of lime) occurred in the sirup 

 pan. During the height of the season the capacity of the equip- 

 ment was hardly sufficient for the number of buckets hung, so 

 that in order to save time on one occasion the daily cleansing of 

 the pan was omitted. A decided darkening was soon noted in the 

 grade of sirup obtained and suspicion was directed towards the 

 sirup pan. The fire was banked and the niter removed. An im- 

 provement of several points in color of the sirup immediatelv 

 resulted, showing that the sugar mechanically included in the 

 niter was being caramelized and was exercising a detrimental 

 influence. After this the color of the sirup was carefullv 

 watched, and whenever a depreciation in color began to appear 

 the niter was removed from the sirup pan and the former light 

 light color of the sirup was restored. 



Conclusions 



Returning now to the questions these studies were inaugu- 

 rated to answer, the work has shown that the depreciation in color 

 and flavor of maple sirup which ordinarily occurs in the com- 

 mercial sugar place as the season progresses is to be attributed t< 1 

 the action of micro-organisms. Certain groups exercise a more 

 detrimental influence upon color than upon flavor, while with other 

 groups the reverse is true. The influence of each group appears 

 more or less specific and characteristic. The most common form 

 of organisms present in maple sap, the fluorescent bacteria, in- 

 jures the flavor much less than it does the color. Those organ- 

 isms which most seriously affect the flavor of sirup, the non- 

 fluorescent, spore-bearing bacteria, molds, and stringy sap organ- 

 isms, do not seriously darken the color. They do. however, fre- 

 quently render the sirup cloudy and so viscid that it does not clear 

 perfectly, even if left undisturbed for months. 



In addition to the depreciation due to bacteria there may 

 occur deterioration due to physiological changes in the tree itself. 



