DETERIORATIVE CHANGES 357 



in the container. Faulty processing must be understood to include faulty 

 sanitation in the plant since heavy contamination of filling lines, etc., 

 with certain types of resistant spore-forming bacteria can result in spoil- 

 age of canned seafoods subject to thermal processing which would be 

 perfectly adequate for foods carrying their normal bacterial populations. 

 Indeed, it may be noted here that most of the bacteria normally present 

 on fresh seafoods are extremely sensitive to heat. 



Food Processing Hazards. Processes which bring about a complete 

 change in the bacterial flora of foods, usually by virtual elimination of 

 the naturally occurring bacteria and their replacement by adventitious 

 forms which may be derived from human or animal sources, introduce 

 the problem of potential food poisoning hazards. Fresh and frozen sea- 

 foods, other than shellfish, have only very rarely been indicted as the 

 source of food poisoning incidents. Fresh molluscan shellfish offer a pe- 

 culiar problem due to their natural method of feeding and their growth 

 in coastal waters which may be exposed to terrigenous pollution. How- 

 ever, the very effective control measures which are practiced in most 

 countries have virtually eliminated the food poisoning hazard implicit 

 in this situation. 



The other fresh seafoods owe their freedom from food poisoning risk to 

 three factors. These are: (a) the absence of food poisoning bacteria in 

 the natural floras (in contradistinction to fowl in which Salmonella occur 

 naturally), (b) the normal practice of holding fish products at low tem- 

 peratures, and (c) the controlling influence of the normal and putrefactive 

 spoilage flora on stored fish. The first point needs no comment. The im- 

 portance of the second point is closely related to the third. Food poisoning 

 organisms will not, in general, grow significantly at low temperatures 

 (i.e., below about 50°F), but the normal flora, since it is primarily psy- 

 chrophilic in nature, will grow quite actively. In situations where the 

 temperature is high enough to permit growth of dangerous organisms, 

 the natural flora will, in most cases, grow very much faster so that the 

 potential pathogens are swamped and eventually die out. There may 

 even be a positively lethal effect on such pathogens from the competitive 

 growth of the spoilage flora. 



In precooked seafoods such as fishsticks, fish dinners, etc., the extremely 

 heat-sensitive natural flora is largely wiped out and may, under poor sani- 

 tary conditions, be replaced by an essentially mesophilic (temperature 

 optimum about 100°F) contaminant flora which may contain significant 

 numbers of bacteria from human sources. The dangers in such a situation 

 are obvious. Very much higher standards of plant sanitation and oper- 

 ator personal hygiene are necessary in plants producing these types of 

 foods than in normal fresh fish processing plants. 



