Viability of Clonorchis sinensis Metacercaria according to the Food-processing Methods

Cho, Yoo Joung; Chu, Jong Phil; Rim, Han Jong; Hwang, Son Kyong

Abstract

BACKGROUND: Endemic areas of Clonorchis sinensis are in Asia including Korea, China, Taiwan and Vietnam. Its metacercariae consumed in uncooked, or undercooked, unfrozen fish can present human a hazard. Purposes of this study are 1) to observe the effect of each food-processing method and each storage method on C. sinensis metacercariae and 2) to suggest basis to be referred as an indicator in prevention.
METHODS
Live metacercariae of C. sinensis in fish collected from Nakdong River in Korea were isolated by pepsin digestion, then were injected into the center of regular-sized muscle protein (1 cm3) of flesh water fish. The sample proteins containing metacercaria were processed according to each food-processing method (heating, frying, boiling) and each storage method (chilling, freezing, pickling with vinegar, salt and soybean sauce). After these procedures, the number of dead metacercariae were counted.
RESULTS
It took 10 seconds to kill all the metacercariae in muscle protein in deep frying (180 degrees C), 30 seconds in boiling (100 degrees C) and 60 seconds in dry heating. Metacercariae did not lose all the viability in 4-6 degrees C after 40 days, but lost in -10degrees C and pickling after 5 days, and in salting (salt and soybean sauce) after 3 days.
CONCLUSION
These results indicated that the storing in low temperature and in such as vinegar, salt, and soybean sauce was not effective to lose the viability unless if it was kept for a long period of time. Among the food-processing methods, frying in soybean oil was the most effective method to lose the viability of metacercariae.