TAIPEI (Taiwan News) -- A study by a researcher at Fu Jen Catholic University has found that the old Taiwanese standbys -- aged braised pork, tea eggs, and pork broth -- could be carcinogenic, especially after cooked for more than three hours.
"The idea that the longer pork is braised in broth, the better, is a mistaken notion," said Chen Bing-huei (陳炳輝), a professor at Fu Jen Catholic University's Department of Food Science, who found in a study that reheating pork broth containing meat, soy sauce, sugar and water produces carcinogenic cholesterol oxidation products (COPs), reported United Daily News on Monday.
According to the results of the study, a basic braised pork broth recipe including pork, soy sauce, rock sugar, and water will immediately start producing COPs when heated. The longer the concoction is heated, the more COPs are produced, and after four hours 35 parts per billion (ppb) will have been produced. After 12 hours, 64 ppb will have been generated, and after 24 hours, the number reaches 78 ppb.
Chen said that a broth only containing soy sauce, water, and rock sugar, does not produce carcinogens upon reheating. In fact, the soy sauce and rock sugar have an antioxidant effect. He added that lowering the broth to a ratio of only one percent soy sauce and one percent sugar, reduces of the production of COPs in the broth by 60 percent. However, once meat is added to the broth, a variety of carcinogens are produced, such as cholesterol, oxidation products, heterocyclic amines, and others that can also increase cardiovascular disease.
Chen recommends that consumers lower the consumption of braised pork broth products, but if they really want to eat them, they should not be heated for more that three hours. Once the broth has been cooked for more than three hours, the carcinogens start to increase and the nutritional value starts to decrease. For instance, he recommended not eating store-bought beef noodles that contain meat that is too soft or rotten. In order to add flavor, the store may have repeatedly cooked the meat many times for long periods.
In response to the report, Yen Tzung-hai (顏宗海), head of the Clinical Toxicology division under the Department of Nephrology at Linkou Chang Gung Memorial Hospital, said that while reheating of meat products, including not only braised pork, but also barbecuing, grilling and deep frying meet can increase COPs, thus far only studies in animals have shown a direct connection in developing cancer.
Yen noted that such dishes are high sodium, calcium, fat and calories, which can all contribute to developing vascular disease. He suggested that consumers eat a balanced diet that includes more fruits and vegetables and is lower in fat, sugar and salt.
A nephrologist at National Taiwan University Hospital, Chiang Chih-kang (姜至剛), said that such braised pork broth my contain a low level of carcinogenic substances, but the average citizen should not be overly concerned because the level of exposure is relatively low. "Would anybody eat a whole pot of braised pork broth?" said Chiang.