ANNUAL REPORT, 1934 61 



The fish meal studies have been continued in a limited way. There is very little 

 difference in the nutritive value of extracted and non-extracted fish meals as 

 supplementary sources of protein for chicks or laying hens. Vacuum-dried meals 

 were significantly superior to flame-dried ones for both rats and chicks. 



Work is now under way to determine the biological value of the proteins of the 

 mackerel and crab by rat feeding experiments. Mackerel oil was found to be a 

 poor source of vitamins A and D. 



The preparation and use of waste fish products as dog foods has been given 

 some attention. 



Home Canning Research. (W. A. Maclinn, Pearl Haddock, C. R. Fellers and 

 W. W. Chenoweth.) A simple new method for the determination of partial 

 pressures in sealed glass containers was perfected. The method of processing fully 

 sealed glass jars of canned food has been successful for all fruits and for most 

 vegetables when processed in the water bath. However, at the present time the 

 method cannot be recommended for canning meats, fish, or vegetables processed 

 in the pressure cooker or oven. Many new data on pressure, headspace, vacuum, 

 venting, heat penetration, and cooling of glass containers during and after heat 

 treatment have been collected. When fully collated these data will help to ex- 

 plain what actually occurs in the jar of food during processing. Oven canning 

 studies show that while this method cannot be recommended for general home 

 use, the type of oven and container are important factors. Small oven loads are 

 sterilized much more rapidly than large ones. The optimum temperature range 

 for the oven is 250° to 300°F. The presence of a pan or tray of water in the oven 

 during processing definitely retards heat transfer in the jars of food. 



Maple Products. (C. R. Fellers.) A paper on the content of vitamins A and C 

 in maple products is in press. The results were all negative. Maple syrup was 

 successfully canned in sealed tin cans and the experimental packs have maintained 

 their original quality for over a year. This method of preserving maple syrup 

 should have wide use. 



Microbiology of Dried Foods. (J. A. Clague in cooperation with the Depart- 

 ment of Bacteriology.) Preliminary studies show that yeasts are destroyed by 

 the usual methods of dehydrating prunes and grapes. Using Esch. coli as an index 

 of intestinal contamination, dehydration effectively destroyed this type of organ- 

 ism. The principal contamination of bulk dried foods is at the surface of the mass. 



Blueberry Investigations. (C. R. Fellers and Oreana Merriam.) Chemical and 

 vitamin C studies were conducted on six cultivated and one wild variety of 

 Vaccinium corymbosum and on wild V. pennsylvanicum from Massachusetts and 

 from Maine. Blueberries are fair to good sources of vitamin C. Little difference 

 in potency was noted among the cultivated varieties, though marked variations 

 in chemical composition were found. Commercial and home methods of canning 

 conserved to a considerable degree the vitamin C of blueberries. Freezing had 

 practically no effect on vitamin C in blueberries. 



