Review
Transition of trans Fatty Acid Contents of Margarines, Fat Spreads and Shortenings in Japan
2025 Volume 74 Issue 4 Pages 341-347
Details
2025 Volume 74 Issue 4 Pages 341-347
Margarine, fat spread, and shortening made with partially hydrogenated fats and oils as their raw materials have been known as foods containing trans fatty acids. Due to concerns about the health effects of trans fatty acids, the content of trans fatty acids in these products has now been reduced to around 1 g/100 g (median value) through the use of alternative oils and fats, which is about the same level as that for vegetable oil used as main raw material. In this review, we summarized the trends in trans fatty acid content in products manufactured in Japan from 1969 to 2022.
Trans fatty acids contained in fats, oils and processed foods are known to increase the risk of coronary heart disease1) ,2) and restrictions on the use of trans fatty acids or partially hydrogenated oils (PHOs) containing trans fatty acids in foods are being promoted in many countries3) . Margarines, fat spreads and shortenings are essential for making bakery products and confectionery. These solid fats have been known as foods containing trans fatty acids because of their history of being manufactured using hydrogenated fats, but since the 1990s, manufacturers have been voluntarily reducing trans fatty acids. This review summarizes the results of analyses of trans fatty acids in margarines, fat spreads and shortenings conducted between 1969 and 2022.
Trans fatty acids in nutrition labeling are defined by the Codex Alimentarius Commission in May 2005 as 〝all the geometrical isomers of monounsaturated and polyunsaturated fatty acids having non-conjugated, interrupted by at least one methylene group, carbon-carbon double bonds in the trans configuration〟4) . Thus, conjugated linoleic acid is excluded from the definition of trans fatty acids, although its structure has a double bond in the trans configuration.Trans fatty acids are known to be formed by the hydrogenation process in the curing process of animal and vegetable oils and fats, by the action of microorganisms in the ruminant’s stomach, and by exposure to high temperatures in the heating and deodorizing process in the refining process5) .Trans fatty acids produced in the hydrogenation process are mostly 18:1 isomers, 9t-18:1 (elaidic acid) , 10t-18:1 and 11t-18:1 (vaccenic acid) as major components6) . Similarly, trans fatty acids from ruminants are mainly composed of 18:1 isomers, but characteristically 11t-18:1 is abundant, accounting for about 50% of the total t-18:1. On the other hand, the major trans fatty acids produced by high temperature exposure are 18:2 and 18:37) , 9c,12t-18:2, 9t,12c-18:2, 9c,12c,15t-18:3, 9c,12t,15c-18:3 and 9t,12c,15c-18:3 (Fig. 1) . These compositions allow for some estimation of the origin of trans fatty acids. In this review, total trans fatty acid content of margarines, fat spread and shortenings is summarized.
Chemical structures of oleic acid and major trans fatty acids.
Trans fatty acids in household margarines, fat spread and shortenings in Japan have been gradually decreasing through corporate efforts since the mid-1990s, when concerns about health effects began to emerge8) . In February 2011, the Consumer Affairs Agency of Japan released 〝Guidelines for the Disclosure of trans Fatty Acids Information〟9) and recommended that food businesses voluntarily disclose information on trans fatty acids in their products. In March 2012, the Food Safety Commission of Japan published on its website the results of its evaluation10) of trans fatty acids in food products, which led to further progress in reducing trans fatty acids in margarines11) .
Overseas, in June 2015, the U.S. Food and Drug Administration (FDA) exempted PHOs containing trans fatty acids from GRAS (generally recognized as safe) 12) and determined that FDA approval is newly required for their use in foods beginning June 2018. In Canada, an inhibition on the use of PHOs (defined as having a iodine value greater than 4) was decided in September 201713) . However, hydrogenated fats and oils with an iodine value of 4 or less are treated as fully hydrogenated fats and oils that do not contain trans fatty acids and are not subject to regulation. Conjugated linoleic acid is also excluded from trans fatty acids. In May 2018, the World Health Organization (WHO) released 〝REPLACE〟14) , an action plan for governments to reduce trans fatty acids produced during the production of processed foods. In response, countries are currently working to set maximum limits for trans fatty acids in foods, mandate the labeling of trans fatty acid content, and regulate the use of PHOs containing trans fatty acids.
Gas chromatography is commonly used for quantitation of trans fatty acid content. In Japan, the Consumer Affairs Agency released 〝Guidelines for Disclosure of trans Fatty Acids Information〟9) in 2011, and AOAC Official Method 996.0615) and AOCS Official Method Ce 1h-0516) (or methods with equivalent performance) were listed as valid analysis methods. Subsequently, AOCS Official Method Ce 1j-0717) and JOCS Standard Method 2.4.4.3-2013 (formerly T17-2007) 18) were considered equivalent to the above methods19) ,20) . They are performed in capillary GC columns of 60 m to 100 m length with highly polar cyanopropylsiloxane as liquid phase (e.g. SP-2560, CP Sil-88) , which are methods that allow practical separation of cis and trans isomers on chromatograms.
In the past, GC using a 30 m capillary column which is insufficient for cis-trans separation, was combined with silver nitrate impregnated thin layer chromatography (e.g., JOCS Standard Method R3-2013 (former T8-2003) 21) ) , or infrared spectroscopy22) . In this review, some of the trans fatty acid contents include results obtained by these methods.
The trans and saturated fatty acid contents of domestic margarines, fat spread and shortenings were extracted from the data of studies subsidized by the Japan Margarine Shortening & Lard Industries Association (2003-2022) 23) ,24) ,25) ,26) ,27) ,28) ,29) ,30) ,31) ,32) ,33) ,34) ,35) ,36) (Table 1) , and their respective trends are shown in Fig. 2. Since the data from 1969 to 2003 and 2008 were expressed as fatty acid composition (%) , the lipid value and factor (0.95) were multiplied to calculate the content.
Means of trans fatty acid content of margarine, fat spread and shortening (g/100 g).
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Trend of trans fatty acid content in margarines fat spreads and shortenings in Japan. (a) Mean value. (b) Median value.
The trans fatty acid content of household margarines and fat spreads showed a clear downward trend in the 2000s. Although the mean value has been raised upward by some brands that contain high levels of trans fatty acids, the median value shows that it has decreased to about 1 g/100 g, the same level as the vegetable fats and oils that are the raw material around 2012. There is no significant difference in 2022 compared to 2018, and it is inferred that further reduction in the processing process will be difficult. The increase in the trans fatty acid content of margarines for bakery in 2011 was due to the inclusion of six products made from hardened fish oil (average trans fatty acid content 10.7 g/100 g) among the 24 brands. Currently, trans fatty acids in margarines are lower than in butter (2.7 g/100 g) . Margarines and fat spreads for bakery use were reduced to the same level as those for household use in 2022, although there were some upward and downward trends, probably due to the small number of analysis samples.
The trans fatty acid content of shortenings has also remained almost unchanged since 2008 although the number of samples analyzed are small. The average trans fatty acid content of shortenings was higher than that of margarines because some of the commercial brands have particularly high trans fatty acid content. On the other hand, the median value was about 1 g/100 g, similar to that of current margarines and fat spreads.
The composition of trans fatty acids in household margarines, fat spreads, and shortenings produced in 2022 had a high percentage of t-18:2 and t-18:3 (Fig. 3) . These trans fatty acids are known to be formed during the heat deodorization process of raw fats and oils. The use of PHOs was inferred because the trans fatty acids in margarines and fat spreads for bakery had a higher percentage of t-18:1 than those in household products (Fig. 4) . However, the t-18:1 in most brands was less than 1 g/100 g, suggesting that the amount was small. In addition, a high percentage of vaccenic acid (11t-18:1) was found in total t-18:1. Butyric acid, which is characteristic of dairy fat, was also detected in eight margarines and six fat spreads for bakery. These results suggest that the detection of the t-18:1 does not imply only the use of PHOs, but also the use of milk fats. The trans fatty acids in shortenings for bakery varied in content and composition. Three shortenings were found to contain very high levels of trans fatty acids. The major trans fatty acids in these brands were t-18:1 isomers, which were thought to be derived from PHOs and accounted for 94% of the total trans fatty acids. Because of the inclusion of these three brands, the mean value of percentage of the t-18:1 in the total trans fatty acids was relatively high at 83%. Excluding these brands, the percentage of t-18:1 isomers in total trans fatty acids was calculated to 48%. Furthermore, the detection of rumenic acid (9c,11t-18:2) suggested that these t-18:1 isomers include those derived from ruminant fats such as tallow, in addition to those derived from PHOs.
Mean values of trans fatty acid composition of household margarines, fat spreads and shortenings produced in 2022.
Mean values of trans fatty acid composition of margarines, fat spreads and shortenings for bakery produced in 2022.
From 2007 to 2009, saturated fatty acid content increased in household margarines (Fig. 5) . This period was when the trans fatty acid content decreased by half, suggesting that PHOs were replaced with palm oil and other saturated oils. After 2009, no significant increase in saturated fatty acids was observed. Therefore, it can be inferred that recent trans fatty acid reduction has not been achieved by replacing PHOs with fats high in saturated fatty acids, but mainly through the use of transesterification and other methods.
Trend of mean values of saturated fatty acid content in margarines, fat spreads and shortenings in Japan.
The trans fatty acids in margarines, fat spreads and shortenings currently available on the market (especially in household products) appear to be at levels that are difficult to reduce further.
The t-18:1 isomers in the product are low, and the t-18:2 and t-18:3 isomers are the main components, suggesting that the trans fatty acids contained are not from PHOs but from vegetable oils and fats that have undergone a heat deodorization process in the raw materials. Also, a small amount of trans fatty acids presumably derived from ruminant fats was included. However, some products still contain high trans fatty acid content. In addition, there are many unknowns regarding the physiological functions of each trans fatty acid isomer. Therefore, the accumulation of knowledge on trans fatty acid content in food products will continue to be important.
This work was conducted with reviewed papers from many researchers and supported by the grant from the Japan Margarine Shortening & Lard Industries Association.
