MAPLE SIRUP PRODUCERS MANUAL 



97 



density sirup), the sirup will appear to solidify 

 on cooling. This solid cake is mostly sugar, but 

 some liquid sirup (mother liquor) is mixed with 

 the sugar. 



Fornintion of Crystal Sugar 



The crystalline or grainy nature of the pre- 

 cipitated sugar is determined by a number of 

 factors, all of which are influential in making 

 the desired type of confection (8i). These factors 

 include the degree of supersaturation, seeding, 

 the rate of cooling, and the amount and time of 

 stirring. 



Large crystals called rock candy, which rep- 

 resent one extreme, are formed when slightly 

 supersaturated sirup (67° to 70° Brix) is cooled 

 slowly and stored for a long time without agita- 

 tion. A glasslike noncrystalline sirup represents 

 the other extreme. This is formed when highly 

 supersaturated sirup (the boiling point is ele- 

 vated ISf F. or more above the boiling point of 

 water) is cooled rapidly to well below room 

 temperature without stirring. The sirup be- 

 comes so viscous that it solidifies before crys- 

 tals can form and grow. If the hot supersatur- 

 ated sugar solution is stirred while it is cooling, 

 the tendency to form crystals increases. The 

 mechanical shock produced by the stirring 

 causes microscopic crystal nuclei to fonn. Con- 

 tinued stirring mixes the crystals throughout 

 the thickened sirup, and they grow in numbers 

 and in size. When the number of crystals is 

 relatively small, stirring causes the largest 

 crystals to grow larger at the expense of the 

 smaller ones. Thus, a grainy sugar tends to 

 become more grainy the longer it is stirred. 



To produce maple sugar with crystals that 

 are imperceptible to the tongue (impalpable), 

 the crystals must be kept very small, even 

 microscopic in size. This is accomplished by first 

 suddenly cooling a hot, highly supersaturated 

 sirup so that a viscid, noncrystalline, glasslike 

 mass is obtained. Then while it is still in the 

 supei'saturated state, fine crystals, called seed, 

 are added to serve as nuclei, and stirring is 

 begun. Since the mass is so highly supersatur- 

 ated, billions of tiny crystals are formed at the 

 same time, and the result is a very fine grained 

 pi'oduct. 



Invert Siigiir 



Although sucrose is the only sugar in sap as 

 it comes from the tree, some of the sucrose is 

 changed into invert sugar as a result of micro- 

 bial fermentation during handling and process- 

 ing. Both sucrose and invert sugar are made up 

 of two simple sugars, dextrose and levulose. In 

 sucrose, these sugars are united chemically as a 

 single molecule; in invert sugar, they occur as 

 separate molecules. 



A small amount of invert sugar is desirable in 

 maple sirup that is to be made into maple sugar 

 and maple confections. Invert sugar tends to 

 reduce supersaturation, that is, more sugar can 

 be held in solution before crystallization occurs. 

 This helps keep the product moist (62). Also, it 

 encourages the formation of exceedingly small 

 sugar crystals. But too little invert sugar in the 

 sirup will cause the product to be grainy; too 

 much may prevent formation of crystals 

 (creaming) as required for making maple 

 cream. In general, all grades of maple sirup 

 contain some invert sugar, the amount varying 

 with the different grades. Fancy has the least; 

 and U.S. Grade B or unclassified, the most. 

 Thus, the grade of sirup should be a determin- 

 ing factor in selecting sirup for making a spe- 

 cific confection. 



A simple chemical test to determine the 

 amount of invert sugar in maple sirup is de- 

 scribed on page 113. If the amount of invert 

 sugar in the sirup is so small that a fine 

 crystalline product cannot be made, a "doctor" 

 solution is required (60). 



'^Doctor" Solutions 



The simplest "doctor" solution and the one 

 most commonly used is U.S. grade B pure 

 maple sirup, which is naturally rich in invert 

 sugar (more than 6 percent, as determined by 

 the chemical test described on p. 113). As a rule, 

 dark sirup made from sap produced during a 

 warm spell contains a high percentage of invert 

 sugar. The addition of 1 pint of this doctor sirup 

 to 6 gallons of maple sirup low in invert sugar 

 (less than 1 percent) usually will correct invert 

 deficiency. 



When sirup with a high content of invert 

 sugar is not available, the doctor solution can 

 be prepared as follows: To 1 gallon of standard- 



