The Centre for Food Safety (CFS) and the Consumer Council (CC) have conducted another joint study on trans fatty acids (TFA) in 2012 to continue monitoring the TFA level, in particular those non-prepackaged food items which are popular in our local population and had been found to contain relatively higher levels of TFA as revealed in previous studies, and to understand the effect of the trade's effort in reducing TFA level in their products over the past few years.


2.    TFA are a type of unsaturated fats, which are mainly formed during the process of hydrogenation of vegetable oils. During hydrogenation, the structure of the fatty acid molecules in the oil changes, which allows the oil to have longer shelf-life and provide desirable texture to the food.

3.    TFA increase the risk for coronary heart disease (CHD) through their negative effect on serum lipids, that is, raising low-density lipoprotein (LDL) cholesterol (often called the "bad" cholesterol) and decreasing high-density lipoprotein (HDL) cholesterol (often called the "good" cholesterol) in the blood. The World Health Organization (WHO) has recommended that energy intake from total fat should be limited, and fat consumption should be shifted away from saturated fat to unsaturated fat and towards the elimination of trans fat. The Joint WHO/Food and Agriculture Organization (FAO) expert consultation has recommended that less than 1% and 10% of daily energy intake should be from TFA and SFA, respectively. For example, an individual with a daily energy intake of 2000 kilocalories should limit the intake of TFA and SFA to less than 2.2 grams and 20 grams per day, respectively.

4.    In response to health concerns over TFA in food internationally and locally, two joint CC studies and one risk assessment study had been conducted and the results were released in 2007, 2008, and 2009 respectively. In addition, a set of Trade Guidelines on Reducing Trans Fats in Food was released in April 2008 by the CFS with a view to encourage the trade and assist them in reducing TFA content in their food products. Moreover, the CFS also issued the Trade Guidelines for Reducing Sugars and Fats in Foods in November this year, to assist the trade in producing and promoting products which have lower fat content.

The Study

5.    This study covered 84 non-prepackaged food samples, comprising 15 food items under four food categories, including (i) cake (i.e. Swiss roll 瑞士卷, cheese cake 芝士蛋糕, pound/plain cake 淨牛油蛋糕), (ii) egg tart, pie and pastry (i.e. egg tart 蛋撻, chicken pie 雞批, croissant 牛角酥, wife cake 老婆餅, tuna/curry puff pastry 咖喱/吞拿魚酥皮卷); (iii) bread (i.e. cream-filled bun with shredded coconut 椰絲奶油包, cocktail bun 雞尾包, garlic bread 蒜蓉包), and (iv) others (i.e. cookie 曲奇, doughnut 冬甩/沙翁, French fries 薯條, and cream soup with puff pastry 酥皮忌廉湯).

6.    The non-prepackaged food samples were purchased from various food establishments including fast-food shops, bakery stores, supermarkets, convenient stores and restaurants in Hong Kong between June and August 2012. The laboratory testing of these individual samples for TFA, saturated fatty acids (SFA), total fat, sugars, sodium, protein, carbohydrates and energy was completed by the Food Research Laboratory of the CFS in September 2012.

7.    The mean TFA content (range) of the 15 tested food items under four food categories were summarised in the table below:

Food category/item No. of samples Mean TFA content (range) (g)
(per 100g of edible food)
Cake 16 0.41 (0.070-0.77)
Swiss roll 瑞士卷 5 0.29 (0.070 - 0.77)
Cheese cake 芝士蛋糕 6 0.44 (0.20 - 0.65)
Pound/Plain cake 淨牛油蛋糕 5 0.50 (0.29 - 0.68)
Egg tart, pie and pastry 28 0.39 (0-1.1)
Egg tart 蛋撻 8 0.22 (0.040 - 0.44)
Chicken pie 雞批 5 0.30 (0.20 - 0.36)
Croissant 牛角酥 5 0.70 (0.29 - 1.1)
Wife cake 老婆餅 5 0.17 (0 - 0.38)
Tuna/curry puff pastry
咖喱 / 吞拿魚酥皮卷
5 0.70 (0.37 - 0.92)
Bread 16 0.21 (0-0.49)
Cream-filled bun with shredded coconut 椰絲奶油包 6 0.31 (0.040 - 0.49)
Cocktail bun 雞尾包 5 0.19 (0.020 - 0.42)
Garlic bread 蒜蓉包 5 0.11 (0 - 0.20)
Others 24 0.19 (0-0.66)
Cookie 曲奇 5 0.33 (0.040 - 0.66)
Doughnut 冬甩 / 沙翁 5 0.16 (0.030 - 0.48)
French fries 薯條 9 0.07 (0.020 - 0.15)
Cream soup with puff pastry 酥皮忌廉湯 5 0.28 (0 - 0.36)
Overall 84 0.30 (0 - 1.1)

8.    As compared with the results of previous studies, there has been a large reduction in the mean TFA contents in the four food categories covered, reflecting the positive effect of the trade's effort in reducing TFA level in their products. It was also noted that the TFA content in some individual samples has reduced dramatically whilst a similar SFA content has been maintained, reflecting that the reduction in TFA without raising the SFA content in foods is practically feasible.

Advice to the Public

Advice to the Trade

More Information

9.    The related article is published in the CHOICE MAGAZINE (Issue 434 released on 14 December 2012) (Chinese only).

December 2012
Risk Assessment Section
Centre for Food Safety
Food and Environmental Hygiene Department