MAPLE SIRUP PRODUCERS MANUAL 



OPERATING THE EVAPORATOR 



49 



Starting the Evaporatoi- 



The sap is run into the evaporator until the 

 bottom of the front pan is covered to a depth of 

 1 inch; then the fire is lit. As soon as the sap 

 begins to boil, the sap inlet float valve is ad- 

 justed to maintain the desired depth of liquid 

 (V2 to 1 inch) in the sirup pan. As water evapo- 

 rates, the float valve admits more sap (fig. 79). 



If sirup has not been made previously, a 

 series of adjustments of the float will be neces- 

 sary to be sure the liquid in the sirup pan i 

 always maintained at a depth of '/., to 1 inch at 

 the point of drawoff. 



The constant addition of sap keeps the sap in 

 the pan dilute. It becomes progressively more 

 concentrated at points farther from the sap 

 inlet. The sirup di-awoff is at the farthest point. 



Saps of different solids concentrations (° Brix) 

 require different adjustments of the inlet-valve 

 regulator to maintain the same depth of sirup 

 in the front pan. The depth of sap in the sap 

 pan must be gi-eater for sap with a Brix value 

 of 1° than for sap with a Brix value of 2° and it 

 must be lower for sap with a Brix value of 3°. 

 By checking the Brix value of the sap in the 

 storage tank, the float valve can be set to 

 maintain the desired depth of sap in the evapo- 

 rator. The Brix value should be checked with a 

 hydrometer every half hour or whenever a new 

 lot of sap is run into the storage tank. This will 

 prevent burning the pan, which might happen 

 with a change to sap with a lower BrLx value 

 unless the depth of liquid is increased. 



The pipeline between the storage tank and 

 the evaporator must be large enough to assure 

 a constant and adequate supply of sap to the 

 evaporator, so that a constant level of sap is 

 maintained. If this pipe is connected to an 

 outside storage tank, it must be insulated to 

 prevent the sap from freezing in the line. Were 

 this to occur, the supply of sap would be cut off 

 and the pans would burn. 



The sap feed line should be equipped with a 

 fast-acting valve that can be used to adjust the 

 flow of sap and to stop the flow when the 

 evaporator is taken out of use. A secondary sap 

 feed line should also be installed. This line 

 should be equipped with a flexible hose long 



enough to reach any part of the evaporator or 

 finishing pan. This is an emergency line for use 

 whenever there is a stoppage in the main feed 

 line or for quickly supplying sap to any part of 

 the evaporator where sap is needed to prevent 

 burning the evaporator. 



Drawing Off the Siiiip 



The boiling point of standard-density sirup is 

 7° F. above the boiling point of water. This is 

 discussed in detail in the section "Elevation of 

 Boiling Point," page 72. 



Any thermometer that has a range of 200° to 

 230° F. and a sufficiently open scale can be used 

 to determine the boiling point of sirup. It 

 should be calibrated in V2° and preferably in V4°. 



With older procedures, it was customary to 

 make finished sirup in the evaporator. It was 

 seldom possible to continuously remove sirup of 

 standard density from the sirup pan, except in 

 very large evaporators. Instead, the sirup was 

 removed discontinuously or in batches. The last 

 channel of the sirup pan was in effect a finish- 

 ing pan. This caused the following undesirable 

 conditions: The sirup channel was seldom iso- 

 lated, so that the turbulence of the boiling sirup 

 caused a constant intermixing of the finished or 

 nearly finished sirup with less concentrated 

 sap. This lengthened the holdup time (time sap 

 is heated) and occurred when heating is a 

 critical factor in flavor and color development. 

 Also, each time a lot of finished sirup was 

 drawn off, some sirup had to be left in the last 

 channel of the evaporator to keep the evapora- 

 tor from burning. The sirup that was left was 

 then mixed with the next lot of dilute sirup. 

 The prolonged heating period darkened the 

 color. 



However, when this procedure is followed, 

 the drawoff valve must be opened as soon as 

 the boiling sirup reaches a temperature 7° F. 

 above that of boiling water. The temperature of 

 the boiling sirup should be watched closely to 

 be sure it neither rises above nor falls below 

 this temperature, and the sirup should be 

 drawn off at a rate to maintain this tempera- 

 ture. If the boiling sirup falls below the proper 

 temperature, the drawoff valve should be closed 

 immediately. 



