ABOUT LOBSTERS 127 



freeze-drying to preserve sensitive drugs, but the proc- 

 ess is difficult and it had never been successfully 

 adapted to low-cost materials like foods. Another diffi- 

 culty is that a considerable amount of heat (heat of 

 sublimation) is required to evaporate the ice crystals. 

 This heat must reach the center of the material, and in 

 the case of most foods the evaporation of crystals near 

 the surface forms a layer of corklike stuff that is an ex- 

 cellent insulator. It keeps heat of sublimation from 

 reaching the interior unless the surface temperature is 

 raised so high that the food spoils. 



Raytheon gets around this problem by putting 

 frozen foods in a vacuum chamber and shooting through 

 them a powerful blast of ultra high-frequency radio 

 energy. The waves agitate the molecules in the interior 

 of the food and generate just enough heat to make the 

 ice crystals turn directly into water vapor. If the job is 

 handled properly, the food loses up to nine-tenths of 

 its weight and turns into a brittle sort of substance 

 while staying far below the freezing point. Chemical 

 changes, which would damage flavor, cannot take place. 

 Even unstable vitamins are preserved. 



Raytheon regards its new process as experimental, 

 and it does not know yet how long freeze-dried foods 

 will keep at room temperature. They can be stored in 

 plastic envelopes filled with nitrogen to prevent oxida- 

 tion, but in the case of meat that contains fat there may 

 be a tendency to deteriorate with time. Elaborate tests 

 are now in progress to find the best ways to package 

 and store them. 



Cautious Raytheon men do not want to predict 

 what effect freeze-drying will have commercially. But 

 they point out that freeze-dried foods can be shipped 

 without costly refrigeration and stored on grocers' or 

 housewives' shelves. 



One of the largest lobster companies has experimented 

 with this or a similar process. It reports that the results 



