ANNUAL REPORT, 1946-47 49 



of light giving the best correlation with visual color changes and the maximum 

 sensitivity must be determined for each product. 



Process Times for Glass-Packed Foods. (J. E. W. McConnell and W. B. 

 Esselen, Jr.) A cooperative project with the Glass Container Manufacturers 

 Institute, the National Canners Association (Washington, D. C., and San Fran- 

 cisco, Calif., laboratories), and the California State Department of Health was 

 undertaken to compare the heating rates and sterilizing values obtained with 

 comparable sizes of glass containers and cans under different retort and process- 

 ing conditions. 



Bentonite suspensions (1 and 5 percent) were used to simulate convection 

 and conduction heating products, respectively, as this offered a stable medium 

 which could be duplicated and used several times in succession. The third type 

 of food product, that exhibiting a "broken curve," could not be satisfactorily 

 represented by a bentonite suspension because the heating characteristics varied 

 with successive runs. Investigation of bentonite suspensions which produce a 

 "broken curve" revealed that the rate of heating has a marked effect on the type 

 of curve obtained. Rapid heating, with its accompanying greater convection 

 currents until close to retort temperature, when the rate of heating and convec- 

 tion currents markedly slow down and permit the suspension to change from a 

 sol to a gel state, is essential in obtaining a good broken curve. 



It was concluded that the longer come-up time used in glass processing and 

 home canning can markedly affect the type of heating curve between cans and 

 glass containers to influence this type of broken curve obtained. 



The Stability of Carotene and Vitamin A in Mixed Rations and the Compara- 

 tive Efficiency of These Components for Egg Production and Growth. (Cooper- 

 ative project with Department of Poultry Husbandry. L. R. Parkinson and C. 

 R. Fellers.) Controlled levels of carotene (derived from alfalfa) and vitamin A 

 (from fish liver oils) were added to broiler rations at the start of the experiments. 

 Periodic determinations indicated that carotene was destroyed more rapidly 

 than vitamin A during the first two weeks of storage; but after two weeks the 

 vitamin A decreased at a more rapid rate. At the end of 8 weeks 61.5 percent 

 of the vitamin A remained, whereas at the 12-week interval only 37 percent of 

 the original amount was left. The broiler ration containing the largest amount 

 of carotene lost 36 percent of its carotene in the first 2 weeks, but at the end of 

 12 weeks 49 percent of the original amount still remained. The ration containing 

 the smaller amount of carotene showed a loss of 36 percent during the first 2 

 weeks, but thereafter the rate of destruction was less, and at the end of 12 weeks 

 62.5 percent of the original amount still remained. 



Superior feathering of broilers was obtained in this experiment by feeding 

 vitamin A in the form of a carotene extract from alfalfa. 



No deficiencies in fleshing were noted regardless of whether carotene from 

 alfalfa or natural vitamin A was fed at equivalent levels. 



Normal egg production was obtained at a level of 3000 International Units of 

 vitamin A per pound of feed, whether this was natural A or carotene extract from 

 alfalfa. There was little difference in egg production at the feeding level of 

 1000 International Units of natural vitamin A per pound of feed. There seems 

 to be no advantage in feeding three times this amount for egg production alone; 

 but to obtain good strong, healthy chicks, a higher level of vitamin A is indicated 

 by the hatchability and viability data. 



