MAPLE SIRUP PRODUCERS MANUAL 



71 



of the finished sirup. If a finishing pan is used, 

 it should be covered immediately when the 

 sirup reaches the correct density. The heat 

 should be reduced to maintain a slow boil until 

 the desired color is obtained. Adding V2 cupful 

 of U.S. Grade C sirup for every 2 gallons of sap 

 will hasten the darkening process. 



SuiTunar\ 



(1) Maple sap and sirup contain only sugar, 

 protein, organic acids, ash, and less than 2 

 percent of material not accounted for but 

 which is of great importance because it 

 includes the color and the flavor substances. 



(2) Sterile maple sap has neither color nor fla- 

 vor. 



(3) Experimental evidence indicates that the 

 color and flavor in maple sirup are related 

 to triose sugars, organic acids, and soluble, 

 ligninlike substances. 



(4) Factors controlling the formation of color 

 and flavor include fermentation, pH, solids 

 concentration, length of boiling time, and 

 the boiling temperature of the sap. 



(5) The shorter the boiling time, irrespective of 

 the quality of the sap, the lighter the color 

 of sirup produced. 



(6) For best sirup — 



(a) Use sap that has not fermented. 



(b) Use speed in collecting and in evapo- 

 rating the sap. 



(c) Keep equipment clean. 



(d) Know the initial Brix value of the 

 sap. 



(7) Higher grades of sirup are usually produced 

 earlier in the season than later on, because 

 the early season temperatures are usually 

 lower and there is less chance of fermenta- 

 tion. 



(8) Sirup that is too light can be darkened by 

 heating the finished sirup. 



CONTROL OF FINISFIED SIRUP 



Finishing the sirup is one of the most exact- 

 ing tasks in maple sirupmaking. The sirup must 

 be drawn from the evaporator or finishing pan 

 at just the right instant; otherwise, its solids 

 content (density) will be either too high or too 

 low. To conform with minimum Federal and 

 State requirements, sirup must have a density 

 of not less than 66.0° Brix at a temperature of 

 68° F. At this density, a little more or a little 

 less evaporation has a relatively large effect on 

 the concentration (table 12). Hence, when using 

 large evaporators capable of evaporating sev- 

 eral hundreds of gallons of water per hour, 

 accurate control of the sirup being drawn off is 

 both important and exacting. 



Viscosity of Maple Sii-up 



Maple sirup having a density of only 0.5° to 1° 

 Brix below standard-density sirup tastes' thin. 

 This is due to the big change in the viscosity of 

 sugar solutions caused by only a slight change 

 in concentration, especially in the range of 

 standard-density sirup. 



Table 13 shows that an increase in the sugar 

 concentration of sucrose solutions up to 30° 

 Brix has little effect on viscosity. For example. 



a solution with a density of 20° Brix at room 

 temperature (68° F.) has a viscosity of 2.3 centi- 

 poises and at 30° Brix only 3.2 centipoises. 

 However, as the concentration of the sugar 

 increases, the viscosity increases at an ex- 

 tremely rapid rate. Thus, to treble the sugar 

 concentration from 20° to 60° Brix increases the 

 viscosity from 2.3 to 44 centipoises — more than 

 a nineteenfold increase. 



The change in viscosity is even more pro- 

 nounced in sucrose solutions with densities in 

 the range of standard sirup (66.0° Brix). 



As shown in the table, the viscosity of sirup 

 at room temperature (68° F.) is lowered 34.8 

 centipoises if its density is 1° Brix below stand- 

 ard density. It is lowered 61.9 centipoises if it is 

 2° Brix below standard density. The lowered 

 viscosity has a marked adverse effect on the 

 keeping quality of the sirup and on its accept- 

 ance by consumers. The tongue is extremely 

 sensitive to these differences. 



The tongue is also sensitive to slight in- 

 creases in the density of sirup above 66.0° Brix 

 at room temperature. An increase of only 1° 

 Brix above standard density increases the vis- 

 cosity of sirup 45.8 centipoises; and the sirup 

 acquires a thick, pleasant feel to the tongue. 



