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Food Safety Focus (142nd Issue, May 2018) – Incident in Focus

Glycidyl Esters, a Harmful Substance, in Refined Fats and Oils

Reported by Mr. Arthur YAU, Scientific Officer,
Risk Assessment Section,
Centre for Food Safety


On 16 April 2018, a local organisation published an article on the result of its study on butter, margarine, fat spreads and shortenings in Hong Kong, which revealed that glycidyl esters (GEs) were found in most margarine, fat spreads, fat blends and shortenings samples, and were not detected in all butter samples. This article aims to discuss how GEs are formed in some fats and oils, the health effects and what is being done on the issue internationally.

Butter versus Margarine and Fat Spreads

Butter is a fatty emulsion derived through physical separation of fat from milk, where no refining is required. On the other hand, margarine and other fat spreads are spreadable fat emulsions that remain solid at  room temperature. They can use many different types of refined fats and oils as ingredients, which may contain GEs.

What are GEs?

GEs are process contaminants which are found in refined fats and oils. They also appear in food that contains these refined fats and oils. When fats and oils undergo the deodorisation step during the refining process (see Figure 1), some of the chemical precursors that are naturally present in the crude oil can react with other compounds in oil at temperatures in excess of 200°C. This issue is of particular concern in certain types of vegetable fats and oils (e.g. palm oil) which has higher levels of the precursors than other oils, where more GEs canbe formed when the right conditions are met during refining.

GEs are broken down during digestion, after consumption resulting in an almost complete release of glycidol. Glycidol is a genotoxic carcinogen and it is best to keep the level of GE in food as low as reasonably achievable. There are possible measures that can reduce the level of GE during various states in oil production. In fact, fats and oils should be part of a healthy diet as they are essential in the absorption of fat-soluble vitamins. The contribution of fats and oils to energy intake should be kept within 20 to 30%, and among them, less than 10% of energy intake should be from saturated fat in a healthy diet. In practice, we should eat less fats and oils as far as possible with reference to the food pyramid.

Figure 1: Refining of edible fats and oils.

Figure 1: Refining of edible fats and oils.

International Developments in Standards and Preventive Measures

Currently, the Codex Alimentarius Committee (Codex) has not set any maximum levels for GEs in  food. The European Union has recently, in February 2018, set maximum levels for GEs at up to 1000 µg/kg (expressed as glycidol) in specified foods, including vegetable fats and oils.

On the other hand, the Codex is developing a Code of Practice (CoP) in reducing the levels of GEs and 3-MCPD esters in food, which is expected to be finalised by 2020. Although the CoP is still under development, it currently focuses on reducing the precursors in the formation of GEs in fats and oils through selection of varieties of oil crops that contain less GEs precursors, selection of fertilisers with less chloride, harvest at the right maturity to avoid excessive breakdown of lipids, and the use of right processing parameters (e.g. lower temperature during deodourisation during refining of edible oil), etc. The Codex reported that it may be better to remove the precursors to GEs at earlier stages of processing than just focusing on the oil refining process. The Centre for Food Safety will keep monitoring the development of the CoP closely and update the trade accordingly.

Key Points to Note:

  1. GEs are process contaminants that are formed during the refining of certain vegetable oils.
  2. The levels of GEs can be reduced through different approaches ranging from farming practices to processing parameters.
  3. The intake of GEs should be kept as low as practically possible.

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