634 MILK 



ice-cream stiff, sticky and spongy, and influence the taste un- 

 favorably. Poor qualities of gelatin should never be used, be- 

 cause they both impair the taste of the product and usually con- 

 tribute enormous quantities of micro-organisms. The gelatin is 

 dissolved in hot water or, better, in hot skimmed milk before it 

 is added to the mixture. 



Eggs are efficient stabilizers, and are used chiefly in French • 

 and Neapolitan ice-creams. They should be well cooked before 

 they are used. 



Rennet coagulates milk and consequently produces a firm 

 body and smooth texture. Girni tragacanth is also not infre- 

 quently used as a stabilizer. A stock solution is made by soak- 

 ing 1 ounce of gum in 1 quart of hot water, and then- dissolving 

 3 pounds of sugar in the same. The sugar acts as a preservative, 

 making it possible for the solution to remain usable for several 

 weeks. One quart of gum tragacanth and sugar solution suffice 

 for 10 gallons of ice-cream, according to Washburn. 



So-called "ice-cream powders" for producing a rich and smooth 

 ice-cream are purchasable in the market. They consist of gelatin 

 or gum tragacanth, or a combination of both. They are tritu- 

 rated with six to ten times their weight of sugar, and are then 

 dusted on the mixture before freezing. Some ice-cream powders 

 contain starchy substances as well, such as flour or cornstarch. 

 Some even have powdered rennet mixed with other stabiUzers. 

 When wheat flour, rice flour, or cornstarch are to be used they 

 should be well cooked before they are added to the mixture. 

 Otherwise a granular textm-e may result.' 



Sugar is always added to ice-cream mixtiu'es, chiefly to in- 

 crease the palatibility of the ice-cream. The quantity of sugar 

 used amounts to about 14 per cent, of the finished product. 



The swell or overrun of ice-cream is due chiefly to the air 

 which is incorporated during the freezing process by the violent 

 agitation. The expansion of the cream also adds somewhat to 

 the overrun. The cream should be viscid in order to retain the 

 air. The swell adds to the palatabihty of ice-cream and fre- 

 quently increases the volume of the product 80 per cent. Slow 

 freezing with continued whipping increases the swell. 



Washburn states that the swell commences to form at 34° F., 

 and ceases to form at 27° F. The maximum is reached at 28.5° F., 

 but the cream should not be removed before the temperature 

 has reached 28° F., otherwise some of the swell is lost by the loss 

 of air. When the swell exceeds 80 per cent, of the mixtiu'e the 

 body of the ice-cream deteriorates. In the chart (Fig. 235) Wash- 

 burn illustrates the relation of temperature to swell. 



A relative test for the quantitative determination of the 



