Trans-fats, also known as trans-fatty acids are a type of unsaturated fatty acids that occur in small amounts in nature but widely produced industrially as a by-product. Naturally occurring trans-fats are made by bacteria that live in the animal rumen such as cattle, sheep and goats. Hence, it may occur naturally in small quantities in animal meats as well as in dairy products like milk, cheese, butter and cream (Saxelby, 2018). While artificial trans-fats are created in an industrial process that adds hydrogen to unsaturated liquid vegetable oils to make them solid through hydrogenation (AHA, 2017). During this process, the oil is heated in the presence of hydrogen and a catalyst to transform them into solid and semi-solid fats.

In the process of full hydrogenation, all double bonds of the oils will be converted to single bonds and all the unsaturated fats will be converted into saturated fats. However, incomplete or partial hydrogenation does happened. Partial hydrogenation converts the cis double bonds into trans double bonds, thus, resulting in trans-fatty acids. All the food or food items prepared with partially hydrogenated oils (PHOs) will contain trans-fats. Its consumption will raise the Low Density and Very Low Density (LDL and VLDL) cholesterol levels as well as lowers the level of High Density (HDL) cholesterol. It also leads to reduced triglyceride uptake and production of free fatty acids (Mozaffarian, 2006). All these factors may cause heart diseases and for every 2% of calories from trans-fat consumption, the risk of heart disease rises by 23% (Harvard 2018). Apart from that, trans-fat is also known as the main causal factor behind harmful diseases such as diabetes, stroke, obesity and cancer.

In the 1990s, one of the first strategies used to remove PHOs from food products was to substitute them with palm oil, which is solid at room temperature due to its high saturated fatty acid (SFA) content. Moreover, palm oil has a higher melting point and special structure of triglycerides that allows it to be incorporated in food products without the hydrogenation process. Due to its special solid fat content, palm oil and its fraction are known as the best candidate in the formulation of trans-free margarine, shortening, vanaspati, specialty fats and also bakery products. Interesterification (IE) is the process of rearranging the fatty esters within and between triglycerides which results in the change of the physical properties of the oils and fats. Of late, it is known as an alternative to hydrogenated fats that give the oils and fats the functionality required for a finished product. Both chemical and enzymatic IE has been used in the formulation of trans-free margarine and shortening which still maintains its physical properties, taste and stability (List et al., 1995).

In November 2020, a research team at the University of Guelph, Canada, proposed an innovative use of enzymatic glycerolysis to directly convert liquid oils into solid fat to be used in place of palm oil and other high-saturated-fat options for food applications (Nicholson and Marangoni, 2020). They postulated that palm oil has led to deforestation, thus, it is necessary to find a means of structuring a variety of readily available vegetable oils to replace palm oil. Enzymatic glycerolysis and enzymatic interesterification are different processes although both involve esterification and the use of enzymes. Enzymatic glycerolysis involves the breakdown of glycerol followed by esterification with fatty acids to obtain mono or diglyceride. On the other hand, enzymatic transesterification involves methanol where the fatty acids from the triglyceride are transesterified. 

Their study showed that by using enzymatic glycerolysis process of cottonseed and peanut oils, they can produced solid fats via the product of monoacylglycerol and diacylglycerol from their native triacylglycerols without the addition of saturated or hydrogenated fat. This will not alter the fatty acid composition and therefore suitable to be used as a new palm oil substitute. It is worth noting that the glycerolysis process needs more controlled conditions compared to transesterification, resulting in an increase in the production cost. In addition, the said process still needs regulatory approval before it may be widely used in the food manufacturing industry and it needs to be well accepted by the food manufacturers.

The use of palm oil as a trans-fat substitute shows no detrimental effects on blood lipid profiles although it has high SFA content. A recent meta-analysis by Fattore at al. (2014) showed that both favorable and unfavorable changes in CHD/ CVD risk markers occurred when palm oil was substituted for the primary dietary fats, whereas only favorable changes occurred when PO was substituted for trans-fatty acids. Palm oil has a whole lot of other health benefits besides being trans-fat free and meeting specific nutritional needs. For instance, it is a rich source of beta-carotene, a precursor of Vitamin A and it also contains tocopherols and tocotrienols. These natural antioxidants act as scavengers of damaging oxygen free radicals. Recent advancements show their biological properties in protection against cancer, cardiovascular diseases, neurodegeneration, oxidative stress and immune regulation (Puvaneswari and Ju Yen, 2016). Palm oil also has been demonstrated to be a necessary component in current dietary recommendations to achieve a balanced distribution between saturates, monounsaturates and polyunsaturates which has a tendency to improve the overall cholesterol lipoprotein ratios upon consumption.

Replacing palm oil with other types of vegetable oils would account for much larger amounts of land use since oil palm trees are the most productive crops compared to others. It is the highest-yielding vegetable oil crop, which makes it very efficient and the least expensive vegetable oil in the world. Given the health benefits of palm oil when used as an ingredient in food and in view of the increasing emphasis on food being free of trans-fat, palm oil will continue to have a huge role in the production of nutritionally safer products.

References

1. Saxelby, C. (2018). 13 trans-fat foods to remove from your diet!
2. https://foodwatch.com.au/blog/fats-and-oils/item/13-trans-fat-foods-to-remove-from-your-diet.html. Accessed on 18.1.2021.
3. American Heart Association. Trans fats (2017). https:// www.heart.org/en/healthy-living/healthy-eating/eat-smart/fats/ trans-fat. Accessed on 19.1.2021.
4. Center for Science in the Public Interest (CSPINET) (2004). About trans fat and partially hydrogenated oils. https:// cspinet.org/resource/qa-about-trans-fat-and-partiallyhydrogenated-oils. Accessed on 22.1.2021
5. Mozaffarian, D., Katan, M.B., Ascherio, A., Stampfer, M.J. and Willett, W.C. (2006). Trans fatty acids and cardiovascular disease. New England Journal of Medicine. 354(15): 1601-1613.
6. Harvard health publishing (2018) Harvard Medical School. The truth about fats: the good, the bad, and the in-between. www.health.harvard.edu/staying-healthy/the-truth-about-fatsbad-and-good. Accessed on 25.1.2021.
7. List, G.R., Pelloso, T., Orthoefer, F., Chrysam, M. and Mounts, T.L. (1995). Preparation and properties of zero trans soya-bean oil margarines. Journal of the American Oil Chemist’s Society. 72(3): 383-384.
8. Nicholson, R. and Marangoni, A.G. (2020). Enzymatic glycerolysis converts vegetable oils into structural fats with the potential to replace palm oil in food products. Nature Food. 1(11):1-9.
9. Fattore, E., Bosetti, C., Brighenti, F., Agostoni, C. and Fattore, G. (2014). Palm oil and blood lipid–related markers of cardiovascular disease: a systematic review and meta-analysis of dietary intervention trials.  American Journal of Clinical Nutrition. 99: 1331-1350.
10. Puvaneswari, M. and Ju-Yen, F. (2016). Biological Properties of Tocotrienols: Evidence in Human Studies. International Journal of Molecular Sciences. 17(11): 1682.