MAPLE SIRUP PRODUCERS MANUAL 



81 



washed into the recovered sirup. The felt is 

 rinsed repeatedly in hot water. The recovered 

 sirup is returned to the evaporator. 



A homemade washer for flat filters is shown 

 in figure 97. By means of an eccentric, the felt 

 is lifted from the hot water and then dunked 

 repeatedly for 15 to 30 minutes until it is clean. 

 No detergent can be used since it would impart 

 an undesirable flavor to the filter. The felts are 

 then hung on racks to dry or drain. Two or 

 three extra felts are required for replacements 

 while the others are being washed. With an 

 efficient washing machine, the felts can be 

 reconditioned for use so easily that some pro- 

 ducers have discontinued using prefilters. 



Filtering: Sfiiiiconcenlrtitcd Siriif} 



When a finishing pan is used, another filter- 

 ing procedure has proved very successful. This 

 procedure takes advantage of these facts: (1) 

 Most of the sugar sand is precipitated (formed) 

 and in suspension when the sap is concentrated 

 to 55° to 60° BrLx, and (2) hot sap at 55° to 60° 



PN-4793 



Figure 97. — A simple type of machine washes flat filters 

 by repeatedly dipping the felts into hot water. 



Brix has a viscosity of only 1..5° centipoises as 

 compared to 5.4° for standard-density sirup. 

 Therefore, when sap has been concentrated to 

 55° to 60° Brix, it is filtered as it is being 

 removed from the evaporator and before it is 

 transferred to the finishing pan. In bringing 

 the sirup to standard density in the finishing 

 pan, a small amount of additional sugar sand 

 (precipitate) may be formed. This is easily re- 

 moved by using another felt filter assembly. 



This final filtration, like all other open filters, 

 permits loss of water as steam that escapes 

 from the hot sirup. This may increase the 

 density of the finished, filtered sirup by as 

 much as 1° Brix. To avoid this, a number of 

 producei-s pump the sirup from the finishing 

 pan through a pipeline to the closed bottling or 

 canning tank. Since this is a closed system, 

 there is no change in the density of the sirup as 

 a result of evaporation. To provide for the final 

 or polishing filtration, an inline, cartridge-type 

 filter is mounted in the pipeline from the finish- 

 ing pan to the holding tank. Two cartridge 

 filters are used, mounted in parallel with sepa- 

 rate control valves so that they can be used 

 alternately. This permits replacing a clogged 

 filter without inteiTupting the sirup finishing 

 and filtering operation. 



Suiiiinai'v 



Sedinientdtiott 



(1) Strain the sirup through a paper prefilter or 

 cheesecloth. 



(2) Place the sirup in settling tanks. 



(3) Allow it to stand until all suspended matter 

 has settled out. (Test by periodically draw- 

 ing a small sample from the tank spigot.) 



(4) Sedimentation is complete when the sirup is 

 ciystal clear as it is drawn off. 



(5) If the sirup is still cloudy at the end of 

 several weeks, it can be clarified only by 

 filtration. 



Filtration {Preferred Method) 



(1) Run the hot, standard-density sirup from 

 the evaporator or finishing tank directly on 

 the filters. 



(2) Use flat (preferably) filters consisting of a 

 prefilter (paper or flannel) above the felt 

 filter. 



