14 



Ihcvse subslaiices tlo iiul lose llu-ii- aclixily in cold storage. 

 Thus, Wright (J. Soc. Cliem. lu<J., 12, 509, 1923) reported 

 that pork, kept for 9 years in the frozen coiidilion, still 

 eontainod some active rifcun'ni A; "Weill, Alonriiiiiand and 

 Michel {C. r. ^uc. BioL 70, 189, 191G) showed that ritamin 

 B, in beef, was not affected by a storage of 8 months at a 

 temperature of - 8° to - 10° ; etc. It is generally thought 

 that non-protein substances should not be affected, as pro- 

 teins are, by low temi)erature and l)y the congelation of 

 the aqueous medium in which they are dissolved or sus- 

 pended. 



2. Enzymes. Spoilage of refrigerated food is, in some 

 instances, attributed to the action of proteolytic enzymes 

 elaborated by bacteria. This type of enzyme has been 

 found by many authors to be active at sub-zero tempera- 

 tures, in some cases, even at -9°. (Cf. Glage, ZtscJir. f. 

 Fleisch. u. Milchhyg. 11, 131, 1901, and Talyract, Ann. 

 llyg. Pub. Set:, 45, 166, 1901.) 



Kovchoff (1907) observed the conversion of protein 

 nitrogen into non-protein nitrogen in various plant tissues, 

 after they had been frozen for 24 hours. The plant pro- 

 teases, he concluded, survive freezing. 



According to Pennington and Hepburn (J. Am. Chem. 

 Soc., 34, 210, 1911), lipase was active in the abdominal fat 

 of chickens after the latter had been kept hard frozen for 

 more than 7 years at temperatures of - 9.4° to - 12.2°. 



Hepburn (1912) demonstrated the presence of oxidase, 

 peroxidase, catalase and reductase in the same material 

 maintained at the temperature indicated for several 

 months or even several years. 



Gertz (1926), studying the oxidizing enzymes of the 

 alga Delesseria sangmnea and of potato tubers, found that, 

 after a stay of 24 hours in the frozen state at -15°, the 

 tubers yielded unimpaired oxidase, as did also the algal 

 sap, previously extruded, and kept frozen for 98 hours at 

 the same temperature. But, after an exposure of 1 hour 

 to -80°, the reaction of these enzymes was weaker. 



