58 



SCIENCE 



[N. S. Vol. LIV. No. 1385 



error to judge the egg content by the value ob- 

 tained in the aforesaid determination. 



Feanui hy-products : J. B. Reed. 



Some fcKtors governing the crystallisation of 

 lactose in ice cream: Harper F. Zoller and 

 Owen E. Williams. A curve is presented as a 

 result of experimental evidence which serves to 

 separate those mixes which will produce sandiness 

 from, those which will not, and is based upon the 

 relationship existing between the protein-serum 

 solids concentration and the concentration of lac- 

 tose within the mix. It is erroneous to calculate 

 the concentration of lactose on the water basis 

 since the total water in the mix is not available 

 to the lactose because of the competition of the 

 other solids. The effect of the proteins within the 

 mix is not to repress the crystallization of lactose, 

 but they act oppositely in increasing concentration. 

 Because of its slow rate of crystallization lactose 

 hydrate is subject to much supercooling and over- 

 saturation. Protein has very little effect upon its 

 rate of growth. The solubility of lactose hydrate 

 according to the best of experimental deductions 

 is 11.15 per cent, at 0° C. In an ice cream mix 

 containing 10 per cent, fat, 14 per cent, of cane 

 sugar and 65 per cent, of water, the above value 

 for lactose reduces to about 8.9 per cent, calcu- 

 lated on the water basis. 



A rotating thermocouple and cold junction de- 

 signed for temperature studies in horizontal power 

 ice cream machines: Harper F. Zoller. A sen- 

 sitive and experimental thermocouple is described 

 and illustrated which has been designed for the 

 purpose of accurately measuring the temperature 

 of the ice cream mix within the freezer when the 

 latter is rotating at full speed. By maintaining 

 an ice-water cold junction aflSxed to the shaft of 

 the freezer along with the thermocouple junctions 

 the small temperature differences within the freezer 

 can be measured with an accuracy of .02° C. This 

 latter is also made possible by the use of a five 

 junction copper-constantan thermocouple (of fine 

 wire for small temperature lag effect) and a po- 

 tentiometric setup embracing a galvanometer of 

 low internal resistance with a potentiometer of 

 microvolt capacity. The unique feature of the 

 instrument is the method of conducting the small 

 e.m.f. from the rapidly rotating shaft to the po- 

 tentiometer without frictional thermoelectric ef- 

 fects. The instrimient has been in regular service 

 for a number of months, has given no trouble, 

 and has measured the rapidly fluctuating tempera- 

 tures within the mix simply and accurately. 



Cases of supercooling during the freezing of ice 

 cream mixes: Harper F. Zoller and Owen E. 

 Williams. By the use of the rotating thermo- 

 couple we have examined the point of separation 

 of ice in a variety of mixes. The measurements 

 were made in a commercial ice cream machine of 

 the Miller type vrith a capacity of five gallons. 

 The freezing point lowering of the mix was -not 

 in harmony with the calculated value, but showed 

 a high supercooling in the mix even in the presence 

 of the swiftly moving beaters and scrapers. The 

 addition of fine particles of substances to promote 

 the formation of crystal nuclei prevented the 

 supercooling of the mix and consequently the 

 freezing was done in a shorter time, and the 

 product was smoother. Both fat and gelatin seem 

 to reduce supercooling in the average mixes. 

 When sand is added to an ice cream mix con- 

 taining 10 per cent, fat and ,0.5 per cent, of gela- 

 tin ice begins to separate at only a slightly higher 

 temperature when the brine is at 10° F. during 

 the freezing process. If the brine is much lower 

 there is a greater difference in the supercooling 

 effect when no sand is present in the above mix. 

 When mixes are frozen which have been made 

 from evaporated milk containing lactose crystal 

 nuclei and they have not been destroyed by pas- 

 teurization, or other means, no supercooling oc- 

 curs. A great deal of importance is attached to 

 the degree of supercooling and its influence upon 

 the texture of the ice cream as it comes from the 

 freezer. 



Black discoloration in canned sweet potatoes: 

 Edw. F. Kohman. The black discoloration which 

 occurs in canned sweet potatoes begins in the 

 bottom of the can where there is usually a semi- 

 liquid starch paste which affords close contact 

 with the can. Eventually it may penetrate the 

 entire content of the can. The black formation 

 is due to the combination of iron dissolved from 

 the can with a tannin-like substance in the po- 

 tatoes. This is localized to a considerable extent 

 just beneath the peel. But as there is also some 

 throughout the potato and especially about the 

 center no change in present methods of peeling 

 would be of advantage. Tannins do not form 

 black compounds with iron unless the latter is in 

 its highest state of oxidation. As air is essential 

 to bring it into this condition, the necessity of 

 tight seams in canned sweet potatoes is emphasized. 



Charles L. Parsons, 



Secretary 



