52 MASS. EXPERIMENT STATION BULLETIN 449 



Notable amounts of aspartic acid and glutamic acid appeared to exist free or 

 in the form of simple peptides or amides in the apple tissue. Tryptophane could 

 not be detected in either the protein preparations or the apple tissue itself. 



Jar Rings for Home Canning. (W. B. Esselen, Jr.) An investigation on the 

 tendency of home-canning jar rings to impart off-flavors to canned foods has been 

 completed. All natural rubber or a combination of natural and synthetic rubber 

 (GR-S) can be used to make jar rings which will not impart undesirable flavors 

 to foods. In using synthetic rubber it is important that the raw material be 

 selected for this particular use. In some cases chemicals added in the fabrication 

 of jar rings such as accelerators or antioxidants can also contribute off-flavors, 

 particularly off-flavors characterized by a bitter taste. Apple sauce was found 

 to be a particularly good canned food for testing jar rings. If the rings which 

 are used to seal the jars have a tendency to cause off-flavors it will sometimes 

 show up after three months storage at room temperature but a six months storage 

 period prior to testing is to be preferred. 



Home Freezing. (W. B. Esselen Jr., J. E. W. McConnell, and N. Glazier.) 

 AX'ork is being continued on the quality of different varieties of fruits grown in 

 this area when frozen. The fruit varieties have been provided through the co- 

 operation of the Department of Pomology. The products frozen during the 1947 

 season included 18 varieties of strawberries, 10 of blueberries, 11 of cherries, 18 

 of raspberries, 17 of plums, 16 of pears, 27 of peaches, and 8 of currants. A 

 number of the varieties of frozen plums were quite attractive and flavorful but 

 there was a tendency for many of them to have a tough skin. Frozen red currants 

 made a very satisfactory dessert fruit. In general the frozen pears lacked flavor 

 and were not considered satisfactory. Some variation in quality from season to 

 season has been observed in the different varieties of frozen fruits. 



Process Times for Glass-Packed Foods. (Cooperative project with the Glass 

 Container Manufacturers Institute, The National Canners Association (Wash- 

 ington, D. C, and San Francisco, Calif., laboratories), and the California State 

 Department of Health.) (J. E. W. McConnell and W. B. Esselen, Jr.) Experi- 

 mental heat penetration data obtained with bentonite suspensions (1 and 5 per- 

 cent) in glass jars of different sizes have been used in working out come-up time 

 and cool correction factors which can be used in the application of Ball's mathe- 

 matical methods for the calculation of process times for low-acid glass-packed 

 foods. The percentage of the come-up time which may be applied as process 

 time for glass containers corresponds very closely to the 42 percent value used 

 for tin cans. 



Under conditions of convection heating, jars appear to heat more slowly than 

 cans of corresponding sizes. Heat penetration data indicated no difference in 

 the heating rates of cans processed in steam and in water. In the case of conduc- 

 tion heating, the heating rate is somewhat faster for cans than for jars, in sizes 

 larger than the "baby food" size. This results in a somewhat greater lethality 

 for a given process for cans than for jars of corresponding sizes, with the exception 

 of the "baby food" size. 



It was found that rapid cooling of 5 percent bentonite in jars or cans can be 

 brought about by high vacuum and adequate headspace. When the vacuum 

 starts to form in the containers during the cool, boiling of the contents frequently 

 occurs, and with this agitation of the contents, rapid cooling results. 



Tin-Treated Glass Containers for Processed Foods. (W. B. Esselen, Jr., and 

 Fagerson.) Glass containers whose inner surfaces had received a thin coating 



