Reporter's concern: How to detect chemical solvents in crushed oil?

Source: Li Jian, Journalist of China Consumer Daily

On May 3, the State Administration of Food and Drug Administration notified that "Hongjingyuan" flax oil was detected, and the detection value of solvent residue was 14.5 mg/kg. As crushing oil, the national standard stipulated that it could not be detected.

Reporters sorted out the results of sampling inspection of edible oils in recent years, and found that the solvent residue items failed to meet the standard, which has become one of the main reasons why some edible oils have repeatedly been on the "black list". Why can chemical solvents be detected in "healthy and good oil" nominally processed by pressing method?

Unqualified solvent residues

In fact, unqualified solvent residues in edible oils have become an "old" problem.

On April 19, the State Administration of Food and Drug Administration issued Circular No. 72 of 2016, in which Tianmao (website) Shengzhou Food Flagship Store sold rapeseed oil, which was commissioned by Xiamen Shengzhou Vegetable Oil Co., Ltd. (hereinafter referred to as Xiamen Shengzhou) and produced by Jiangsu Shengzhou Grain and Oil Industry Co., Ltd. with the detection value of solvent residue of 15.2 mg/kg.

On April 7, Anqing Pure Vegetable Oil Co., Ltd. produced a bottle of pure good oil solvent residues exceeding the standard, according to the information of food safety supervision and sampling released by Anhui Food and Drug Administration.

On January 27, the sampling results released by Beijing Food and Drug Administration showed that the "Hongjingyuan" rapeseed oil sold by Beijing Supermarket Fa Apple Garden Store was found to have unqualified solvent residues and fatty acid composition.

On June 30, 2015, the State Administration of Food and Drug Administration announced the 13th phase of food safety supervision and sampling inspection in 2015, in which the rapeseed oil produced by Changsha Tonghua Oil and Fat Co., Ltd. was found to have excessive solvent residues.

In April 2014, Weifang Food and Drug Administration of Shandong Province carried out special supervision and sampling inspection of edible oil in the whole city. Three batches of cottonseed oil were sampled and one batch was unqualified. One of the unqualified items was solvent residue exceeding the standard.

Li Shuguo, an expert of Hebei Food Safety Expert Committee and a professor at the College of Bioscience and Engineering, Hebei University of Science and Technology, told reporters that the production process of edible vegetable oil at home and abroad is divided into leaching method and pressing method. Leaching method refers to the use of chemical solvents to extract vegetable oil, and then remove the solvent. Pressing method refers to the use of external pressure to extrude the oil in the oil.

"The hygienic standard for edible vegetable oil GB2716-2005 stipulates that the residual solvent of edible vegetable oil produced by leaching method is less than 50 mg/kg, which meets the standard, while the vegetable oil produced by pressing method can not be detected (less than 10 mg/kg is deemed to be undetected).

Li Shuguo pointed out that it is normal for vegetable oil produced by leaching to detect solvent residues as long as it does not exceed the standard.

The reasons are complicated.

Reporters searched the above 72 and 79 sample inspection announcements issued by the State Administration of Food and Drug Administration this year, and found that rapeseed oil and linseed oil involved in the solvent residue project did not meet the standards were labeled as "pressing".

According to Li Shuguo's analysis:

"Edible vegetable oil produced by pressing is not necessarily completely insulated from solvent residues, and the causes of solvent residues are complex.

On the one hand, in order to improve economic benefits, some production enterprises, although nominally processed by pressing technology, actually use leaching method to produce.

On the other hand, when vegetable oil is produced by pressing method, in order to improve the oil yield, enterprises will stir-fry the oil at high temperature. Vegetable oil may produce trace PAHs in this case.

In addition, it is possible to detect hydrocarbons in crushed vegetable oils due to oil contamination or oil leakage.

Luo Yongzhong, executive director and senior engineer of the Fat Professional Society of China Cereal and Oil Society, analyzed that a few illegal manufacturers did not purchase solvent oil through regular channels, or did not produce it according to the technological procedures prescribed by the state, and some even intentionally adulterated it in qualified bulk oils, which may lead to the detection of solvent residues in nominally pressed edible oils.

During the interview, the reporter found that many consumers did not understand the information about solvent residues in edible vegetable oil. "I buy oil mainly on raw materials, as long as it is non-GMO, big brand, I think it is good oil. What does residual solvent mean? How can I see that? On May 13, Ms. Han, who is shopping at Jiayuan Agricultural Products Store in Shijiazhuang, told reporters.

Needless to say "dip" discoloration

Data show that 90% of vegetable oils in foreign countries are produced by leaching method, and most of edible vegetable oils in China are also produced by leaching method.

"Judging from the development history of edible oil production technology in the world, the leaching process is the most advanced production technology recognized internationally at present." Ding Fuqi, chairman of the expert group of the Oil Branch of China Cereal and Oil Society, said that some enterprises often choose two processes of pressing and leaching according to different needs in the production process. Through the complementarity of the two processes, they can make full use of raw materials and reduce the consumption of solvents.

Similar to Ding Fuqi's point of view, Li Shuguo also believes that edible vegetable oils produced by any process are qualified products as long as they meet the national standards and do not harm the human body, so it is not necessary to talk about "dipping" color change.

In terms of technology and production management, in order to avoid excessive solvent residues, oil companies need to strengthen the monitoring of crude oil desolvation process, strictly monitor the temperature and time of desolvation, and prevent the leakage of lubricating oil from machinery and equipment to pollute vegetable oil.

According to the above-mentioned sample inspection Circular of the State Administration of Food and Drug Administration, the provincial food and drug regulatory authorities in the locality of the production enterprises have ordered the enterprises to inspect the unqualified products found in the sample inspection.