98 



AGRICULTURE HANDBOOK 134, U.S. DEPT. OF AGRICULTURE 



density maple sirup add 2V2 liquid ounces of 

 invertase (an enzyme that causes the inversion 

 of sucrose to invert sugar). Stir the mixture 

 thoroughly and allow it to stand at room tem- 

 perature (65° F. or above) for several days. Dur- 

 ing this time sufficient invert sugar will form so 

 that 1 pint of this solution can be used to doctor 

 6 gallons of maple sirup low jn invert sugar. 

 Invertase may be purchased from any of the 

 confection manufacturers. 



Another convenient type of doctor is an acid 

 salt such as cream of tartar (potassium acid 

 tartrate). Addition of V2 teaspoon of cream of 

 tartar to 1 gallon of low- in vert sirup just before 

 it is boiled for candymaking will cause sufficient 

 acid hydrolysis or inversion of the sucrose to 

 form the desired amount of invert sugar. 



Maple Cream or Butter 



The amount of the maple sirup crop that is 

 being converted into maple cream or butter has 

 been increasing rapidly. Some producers have 

 built up so large a demand for this confection 

 that they convert their entire sirup crop to 

 cream. Some producers make from 2 to 3 tons of 

 this confection annually. 



Maple cream (8i, 85), a fondant-type confec- 

 tion, is a spread of butterlike consistency. It is 

 made up of millions of microscopic sugar crys- 

 tals interspaced with a thin coating of satu- 

 rated sirup (mother liquor). The crystals are 

 impalpable to the tongue and give the cream a 

 smooth, nongritty texture. The first step in 

 making maple cream is to make a supersatur- 

 ated sugar solution. This solution is cooled to 

 room temperature so quickly that crystals have 

 no chance to form. The cooled, glasslike mass is 

 then stirred, which produces the mechanical 

 shock necessary to start crystallization. 



Sirup for Creaming 



For best results, U.S. Grade AA (Fancy) or 

 U.S. Grade A (No. 1) maple sirup should be used. 

 However, any sirup may be used provided it 

 contains less than 4 percent of invert sugar. 



Invert Sugar Content 



The amount of invert sugar in the sirup 

 selected for creaming should be determined by 

 the simple chemical test described on page 113. 



Sirup that contains from 0.5 to 2 percent of 

 invert sugar should make a fine-textured cream 

 that feels smooth to the tongue. Sirup with 

 from 2 to 4 percent of invert sugar can be made 

 into cream by heating it to 25° F. above the 

 boiling point of water (instead of the usual 22° 

 to 24°). Sirup with more than 4 percent of invert 

 sugar is not suitable for creaming. It will not 

 crystallize, or it will crystallize only if heated to 

 a much higher-than-normal temperature. How- 

 ever, the cream will be too fluid and probably 

 will separate a few days after it is made. 



The belief throughout the maple- producing 

 area that maple cream should be made only 

 from first-run sirup and that all first-run sirup 

 will yield a good cream is false. It is the amount 

 of invert sugar in the sirup that determines its 

 suitability for creaming, not the run of sap from 

 which the sirup is made. The amount of invert 

 sugar formed is directly proportional to the 

 amount of microbial fermentation of the sap. 

 This, in turn, is related to the temperature. 

 Unseasonably warm weather is not uncommon 

 during the first period of sap flow. Warm 

 weather favors fermentation of the sap, and 

 sufficient invert sugar is produced to make the 

 early-run sirup unsuitable for making into 

 cream. 



Since most Fancy and Grade A sirup nor- 

 mally contains an adequate amount of invert 

 sugar, the use of a doctor solution is not recom- 

 mended. The addition or formation of too much 

 invert sugar will ruin the sirup. Sirup for 

 creaming should be selected on the basis of the 

 quick test for invert sugar. 



Cooking an(t Cooling 



The sirup is heated to a temperature 22° to 

 24° F. above the boiling point of water (37). (The 

 temperature of boiling water must be estab- 

 lished at the time the sirup is boiled for cream- 

 ing.) The boiling temperature indirectly adjusts 

 the amount of sirup (mother liquor) left sur- 

 rounding the crystals; this, in turn, governs the 

 stiffness of the final product. As soon as the 

 boiling sirup reaches the desired temperature, 

 it should be removed from the heat and cooled 

 quickly. If the cooked sirup is left on the hot 

 stove (even with the heat turned off), enough 

 additional water will be evaporated to produce 

 a more concentrated sirup than desired. 



