114 EXPERIMENT STATION EECORD. 



used in the test were shown to have much to do with the increase of the micro- 

 organisms. 



It having been determined that large numbers of micro-organisms are inti- 

 mately associated with the spoilage of sap, some field tests were made to de- 

 termine their effect upon the quality of the sirup. Several hundred pure 

 cultures of organisms were isolated from various types of spoiled sap, and a 

 number of these were tested on other saps. In some cases the saps used for the 

 purpose were obtained under comparatively aseptic conditions, whereas in others 

 they were pasteurized before incubation. Following inoculation, and after a 

 suitable period of incubation, the saps were concentrated to sirup under uniform 

 conditions. Some late run but not heavily infected saps were also observed in 

 the tests. The 128 sirups, after a period of keeping in the dark, were scored 

 for flavor by an expert who knew nothing with reference to the history of the 

 samples. Not a single case of contradiction as to grade occurred upon rear- 

 rangement and rescoring. In addition, the color, by the method proposed by 

 Bryan (E. S. R., 24, p. 266), number of organisms, reaction, sucrose, invert 

 sugar, and ratio of sucrose to invert sugar were determined, both before and 

 after storing. 



The organisms used in the inoculation tests were fluorescent organisms, non- 

 fluorescent organisms from various sources, Bacillus aceris, gray yeast, red 

 yeast, green mold, a composite culture of molds, yeasts, and fluorescent bacteria, 

 or yeasts and bacteria, pink coccus, pink yeast, and organisms of the B. suMills 

 group (these wei'e accidental infections). The yeasts in some instances did not 

 develop well in the sap, consequently the bacteria gained the upper hand. 



On comparing sirups made from inoculated sap with that from natural sour 

 sap, it was found that those from the naturally infected saps were of the worst 

 quality. The sirups showing the next gi'eatest depr»ciation were those inocu- 

 lated by the green fluorescent bacteria. " The spore-bearing bacteria, green 

 molds, B. aceris, both groups of yeasts, and the natural sour material, occupy 

 positions below the fluorescent group. . . . The statistical tables show that the 

 dark color of late run sirup is to be attributed to the action of micro-organisms, 

 since the sirups made from last run material gathered without infection were 

 always of a light hue. The average depreciation in color as calculated upon the 

 first run controls was 0.8 point. . . . 



" Certain groups exercise a more deti'imental 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, injures the flavor 

 much less than it does the color. Those organisms which most seriously affect 

 the flavor of sirup, the nonfluorescent, s-pore-bearing bacteria, molds, and stringy 

 sap organisms, do not seriously darken the color. They do, however, frequently 

 render the sirup cloudy and so viscid that it does not clear perfectly, even if 

 left undisturbed for months. ... In certain seasons these changes which pro- 

 duce the ' buddy ' flavor may not occur in Vermont until after the sap flow 

 ceases. In ordinary years, however, the season is interrupted by periods of 

 growing weather, so that the vegetative activity of the tree is resumed some 

 time before the flnal discontinuance of night freezes, and the influence of these 

 physiological changes becomes manifest in the true buddy flavor which appears 

 In the sirup. Fonnerly the opinion was commonly held that this depreciation 

 was due to the presence of a relatively large proportion of invert sugar. The 

 analytical data demonstrates that this view is erroneous. There is a decline 

 rather than an increase in the content of invert sugar as the season advances. 

 The exact nature of the cause of the true buddy flavor is unknown." 



Methods of remedying the defects in maple sirup are described. 



