LPT 321: Meat Science (1+1)

EFFECTS OF FREEZING ON MICRO-ORGANISMS AND PARASITES

• Effect of freezing on the pathogenic microorganisms and parasites
• Freezing destroys some bacteria but in other, the temperature is merely inhibiting their growth and multiplication until conditions favorable to their growth appear.
• Freezing, is therefore of, no great values as a method of reducing carcasses affected with pathogenic bacteria safe for human consumption or bacteria commonly found on the beef carcasses destroyed by slow or short freezing.
• Anthrax bacilli can withstand at -130˚C while organism of salmonella group can with stand at -175˚C for 3 days.
• A tubercle bacillus is found viable for over 2 years in carcasses frozen at -10˚C.
• The foot and mouth virus can review viable for 76 days, if the carcasses of animals slaughtered during incubation period of the disease and chilled or frozen immediately afterwards.
• Under similar conditions swine fever virus remain infective in the bone marrow for atleast 73 days and the virus has been shown to be viable in frozen pork for 1500 days.
• Freezing, however, is a valuable method for the treatment of certain parasitic infestation and pork affected with Cysticercus cellulosae can be rendered safe if held for 4 days at -10.5 to -8˚C.
• Carcass of beef affected with Cysticercus bovis can be rendered safe by holding for 3 weeks at a temperature of not exceeding -6.5˚C or by holding for 2 weeks at a temperature of not exceeding -10.5˚C.
• Trichinella cysts in pork are destroyed by holding the carcasses for 20 days at -15˚C or by quick freezing for 24 hours at -18˚C.