ZoBell — 198 — Marine Microbiology 



terial flora of lobsters, rapidly produced ammonia and H2S after the lob- 

 sters were scalded. The H2S reacted with iron in the lobster flesh, result- 

 ing in undesirable blackening. Prompt acidification of the prepared meat, 

 followed by immediate sterilization, proved to be remedial. Canneries 

 are confronted by the additional difficulty that the raw material is usually 

 not delivered in as fresh condition as that in which meat, fruit, or vege- 

 tables can be procured. No conceivable canning process can correct prior 

 decomposition. 



In an effort to determine the cause of the rapid spoilage of fish and its 

 attendant large economic loss to man, Lucke and Schwartz (1937) made 

 a bacteriological study at various times during the process of catching and 

 marketing fish. The bacterial content of the high seas, about 50 bacteria 

 per ml., was not regarded as the serious source of infection encountered in 

 polluted near-shore water, which in many places contained millions of 

 bacteria per ml. Fishes taken from water having a high bacterial content 

 did not keep well and had an offensive taste. The fish seemed to become 

 infected by handling on board ship, particularly when handled in such a 

 way that the intestinal contents were voided or the skin broken. 



The bacteria of polluted sea water, ice, and fish holds were regarded by 

 Lucke and Schwartz as being secondary sources of infection. They em- 

 phasized the importance of proper kilHng, cleaning, and washing proce- 

 dures to minimize bacterial spoilage. Bacteria were found to multiply 

 rapidly in infected fish, even in iced holds, resulting in relatively high bac- 

 terial counts by the time that the fish were unloaded in port. Conse- 

 quently the fish were subject to rapid spoilage on shore unless frozen. A 

 mixture of salt and ice instead of ice alone was recommended in order to 

 obtain a temperature sufficiently low to retard effectively the multipli- 

 cation of spoilage bacteria. Similar observations were made by Wood 

 (1939) who also stressed the importance of proper handling and refriger- 

 ation. The value of benzoates, nitrites, and other preservatives used in 

 conjunction with ice to allay spoilage is discussed by Tarr and Sunder- 

 land (1940) and by Tanner (1944). 



Frozen fish were observed by Stewart (1935) to spoil more rapidly 

 when permitted to thaw than when held at the same temperature without 

 previous freezing. She recommends refrigeration temperatures of from 



— 12° to — 21° C. for prolonged preservation of marine fish. Reay (1935) 

 confirmed Stewart's observations on the effects of alternate freezing and 

 thawing, but he found that fish could not be kept indefinitely even at 



— 21° C. without undergoing undesirable changes in quality. 



An appalling quantity of obviously spoiled fish is dumped or processed 

 for fertilizer owing to inadequate control of microbial processes prior to 

 the delivery of the fish to the retailer or cannery. There is a division of 

 opinion among authorities regarding how much decomposition is allow- 

 able before the food is no longer fit for human consumption. Fish and 

 other marine foods which are partially pre-digested by certain non- 

 pathogenic bacteria may be entirely wholesome, but those which have 

 been properly preserved are generally more palatable. The solution of 

 this problem presents a challenge to the marine microbiologist and food 

 technologist. 



Food inspectors have been guided by one or more of the following 

 properties of commercial fish in passing upon its freshness or eatability : 

 Discoloration, physical consistency, odor, bacterial population, ammonia 

 content, trimethylamine value (Beatty and Gibbons, 1937), and tyrosine 



