In addition to the five standards for testing swill oil, experts suggest adding tests for two carcinogens
After Qiangguan Company's "Quantong Lard" was found to have been blended with gutter oil, the Food and Drug Administration of the Ministry of Health and Welfare published the "Inspection Items and Methods for Oil Products," using the five items of "heavy metals: arsenic, lead, mercury, copper, tin, chromium," "aflatoxin," "acid value," "benzo(a)pyrene," and "total polar materials" as the criteria for judging whether inferior oil blended with gutter oil has been purchased.
But a food processing expert, judging from the production process of gutter oil, believes that the existing oil inspection items are not enough to determine whether edible oil has been blended with gutter oil, nor can they identify the hazards of inferior edible oil.
Chen Chun-cheng, an adjunct lecturer in the Department of Health and Nutrition at Chinese Culture University, in an article titled "A Review of Sanitation Inspection Items for Gutter Oil," called on government agencies to additionally test inferior edible oil products for "acrylamide" and "3-MPC ester (3-monochloropropanediol esters)" in order to identify whether oil products have been blended with waste cooking oil or gutter oil.
The following is his letter:
〈A Review of Sanitation Inspection Items for Gutter Oil〉
By Chen Chun-cheng, adjunct lecturer in the Department of Health and Nutrition at Chinese Culture University
After the horrifying gutter oil incident occurred, the Ministry of Health and Welfare announced its sanitation inspection items on September 5, and the announced inspection items include:
(1) Heavy metals: arsenic, lead, mercury, copper, tin, chromium.
(2) Aflatoxin
(3) Acid value
(4) Benzo(a)pyrene
(5) Total polar materials
The above inspection items are explained as follows:
Item 1: Heavy metals
Heavy metal testing can be said to be a routine inspection item and the basic equipment of food safety testing, so it should be tested.
Item 2: Aflatoxin
Aflatoxin testing is not an important toxicological test item for oils and fats. According to the carcinogenic toxicant data of the International Agency for Research on Cancer (IARC), aflatoxin is only slightly soluble in polar solvents (such as water), insoluble in nonpolar solvents (oils and fats), and highly soluble in moderately polar solvents. Oils and fats are nonpolar substances, so the chance of dissolving in oils and fats is not high, and the residual amount should not be high. The significance of testing for aflatoxin is not great.
Item 3: Acid value
After oils and fats become rancid, the amount of free fatty acids increases, raising the acid value. This is one of the standard items for testing the quality of oils and fats. However, the acid value can be adjusted. As long as an alkali (such as sodium hydroxide) is added to high-acid-value oils and fats to saponify and remove the free fatty acids, the acid value can be significantly reduced. It is a very easy item to correct. As long as it has been refined through alkali treatment, it can pass this test.
Item 4: Benzo(a)pyrene testing
Benzo(a)pyrene is a Group 1 strong carcinogenic toxicant, mainly produced by the combustion of substances such as coal, crude oil, petroleum, natural gas, and wood. Its main food sources are smoked, grilled, and roasted dehydrated foods. It is slightly soluble in water and soluble in alcohols. Oils and fats are not an important source of benzo(a)pyrene, so the probability of detecting excessive benzo(a)pyrene in gutter oil should not be high.
Item 5: Total polar materials
Total polar compounds refer to the sum of compounds with chemical polarity produced when oils and fats undergo cracking or polymerization upon heating. Total polar compounds can also be removed through alkalization and physical refining. Unless the recycled oil is not refined again, the test result will also be qualified.
Recommendation: Two carcinogen tests should be added
Based on the above inspection items, it may not be easy to detect gutter oil, nor can it highlight the food safety problems of gutter oil. It is recommended to add tests for two carcinogenic substances, explained as follows:
Item 1: Acrylamide
Acrylamide is formed by the reaction of naturally occurring sugars in food with asparagine at temperatures above 120 degrees C, and is also part of the Maillard reaction. This substance is classified by IARC as a Group 2A probable carcinogenic toxicant.
If muscle or internal organs are not thoroughly removed from waste carcass raw materials, or if poor storage conditions allow microorganisms to grow, the amount of this toxicant generated during the heating and oil extraction process will be increased. Lard produced under hygienic conditions and qualified processes will not exceed the standard.
In the case of using recycled waste frying oil as raw material, the content of this toxicant will also increase, because in actual operations, when frying meat, it is usually marinated first, and marinating materials often include added sucrose and starch. With the meat itself containing asparagine, high-temperature frying will cause the frying oil to contain acrylamide; frying potatoes in vegetable oil will produce even more acrylamide, and recycling the waste oil for refining and reuse is even more dangerous.
Item 2: 3-MPC ester (3-monochloropropanediol esters)
"3-monochloropropanediol esters" are a carcinogenic toxicant unique to oils and fats, classified by IARC as Group 2B carcinogens, substances that may cause cancer in humans. They are formed from triglycerides into a cyclic acyloxonium ion, which then reacts with chloride ions to form 3-monochloropropanediol esters.
In the case of using recycled frying oil as raw material, this toxicant is more likely to be produced. This is because marinating during the frying process and sprinkling seasoning over the frying pan will allow table salt (sodium chloride) to enter the frying oil, and after prolonged high-temperature frying, this toxin is easily produced. Fresh, qualified lard has no such concern.