'Trans fatty acids' labelled on food product creates a major concern among consumers. Trans fatty acids are naturally found in food products such as milk, butter and lamb fats. In industrial scale, trans fatty acids are commercially produced as the undesired by product of partial hydrogenation process of vegetable oil. During partial hydrogenation, some of the cis double bonds in vegetable oil fatty acids change to trans double bond resulting in trans fatty acid which resemble saturated fats in a semi-solid or solid form with improved stability as shown in Figure 1. This would allow the usage of partially hydrogenated vegetable fat as replacement of animal fat. However, the presence of trans fatty acids in food products are undesirable as it is associated with the risk of coronary heart disease. Thus, to overcome this problem, palm fat has been introduced as an alternative of partially hydrogenated fat in products such as cocoa butter replacer and fat spread. 

Figure 1 : Hydrogenation process of unsaturated vegetable oil

The liquid properties of vegetable oil restricts the usage of the oil for the production of various types of semi-solid or solid products as replacement of animal fats. Hydrogenation is a process of Trans fatty acids have also been commercially produced as a by-product of hydrogenation process in food products in food industry.

      A)    Cocoa butter replacer

Cocoa butter replacer (CBR) is a confectionary of fat substitute which was traditionally produced through partial hydrogenation of liquid vegetable oils such as palm, soybean, cotton, corn, peanut, safflower and sunflower oil with moderate compatibility with cocoa butter about 20% maximum in fat phase. These oils are commonly hydrogenated alone or blended under selective conditions to provide steep SFC melting curves. It is categorised as non-lauric and non-tempering confectionary fat which could impart gloss retention and sharp meltdown to the final products. CBR has high tolerance of about 25% to cocoa butter due to the similarity of CBR in terms of the chain length and molecular weight as cocoa butter which makes it compatible to cocoa butter.  However, partial hydrogenation of vegetable oils to produce CBR results in the formation of high level of  about 46% trans fatty acids which is seen as a risk in cardiovascular diseases. In order to produce CBR with desired properties in presence of low or zero trans fatty acids, various alternatives have been discovered by researchers which utilizes palm fat.

Palm fat can be used as replacement of the partially hydrogenated vegetable fats in cocoa butter replacer through physical and chemical modification of palm oil such as dry fractionation and interesterification respectively. Dry fractionation consist of two steps. During dry fractionation, oil is partially crystallized by controlled cooling of the molten feed to the desired fractionation temperature, holding the partially crystallized slurry for crystal growth followed by the second step where filtration is done by using a membrane filter press. The physical nature of palm oil exhibit a semi-solid state which allows the separation of the low melting fraction, olein and high melting fraction, stearin as shown in Figure 2 below. The olein is then further fractionated into hard palm mid fraction to suit the melting point required for cocoa butter replacer. Palm oil with a source of POP (2-oleo-dipalmitin), at high level of POP upon fractionation, it is suitable to be used fat in cocoa butter replacer. The content of palm mid fraction is increased during the fractionation process with final enrichment of 65% of POP. This specific composition of hard palm mid fraction has very steep melting point as similar to cocoa butter.

Figure 2: Dry fractionation of palm oil

Interesterification is chemical modification method which can be imposed on the palm fat to act as a hydrogenated fat replacer in cocoa butter replacer. There are chemical and enzymatic interesterification method, but, enzymatic method is more preferred as enzymatic interesterification method is a continuous process in which the feedstock of the fractioned palm fat is pumped through a packed bed columns filled with immobilized enzyme and placed in series. The random enzymatic interesterification involves the rearrangement of acyl group between triacylglycerol in palm fat which results in the changes of physical properties of palm fat in terms of solid fat content, melting point, hardness and crystallisation behaviour. The common enzyme used as catalyst in enzymatic interesterification is lipase as shown in Figure 3. Lipase- catalysed interesterification is the best method to produce cocoa butter replacer with very similar triacylglycerol composition of cocoa butter. The regiospecificity of the 1, 3-specific lipase helps in the incorporation of the saturated fatty acids in the 1- and 3- positions of palm oil until a similar triacylglycerol arrangement of cocoa butter is obtained. The enzymatic interesterification leads to the production of cocoa butter replacer with melting point compatible to cocoa butter. The melting point and solid fat content of palm oil increases as it is interesterified. In recent times, the combination of dry fractionation and enzymatic interesterification is being used widely to produce cocoa butter replacer with high quality and cost effective.

Figure 3 : Random enzymatic interesterification mechanism

      B)    Fat spread

Palm fat can be used as hydrogenated fat replacer in fat spreads due to the semi-solid consistency which do not need hydrogenation process which produces undesired trans fatty acids and it crystallizes in beta prime form. This characteristics allows palm fat to be used as fat source in the production of fat spread. According to Food Regulation 1985, regulation 186 , fat spread shall be food in the form of spreadable emulsion of edible fat or edible oil or both, and is capable of being used for the same purpose as butter or margarine. Fat spread shall contain not less than 20 per cent of fat. Physical and chemical modifications of palm fat could produce fat spread with desired textural and organoleptic properties. Fractionation and interesterification of palm fat as discussed in cocoa butter replacer can be used to produce fat spread with low or zero trans fatty acid content.

REFERENCES 

1)      Abigora, R. D., Marmer, W. N., Foglia, T. A., Jones, K. C., DiCiccio, R. J., Ashby, R., &  Uadia, P. O. (2003). Production of Cocoa Butter-like Fats by the Lipase-Catalyzed Interesterification of Palm Oil and Hydrogenated Soybean Oil. JAOCS.

2)      Arellano, M., Norton, I., & Smith, P. (2015). Specialty oils and fats in margarines and low fat spreads.

3)    Berger, K. G. (2007). Trans-Free Fats With the Products of the Oil Palm- a Selective Review. Czech Journal of Food Science, 174-181.

4)      David C. Klonoff, M. F. (2007). Replacements for Trans Fats—Will There Be an Oil Shortage? Journal of Diabetes Science and Technology, 1(3).

5)      HASSIM, N. A., & DIAN, N. L. (2017). USAGE OF PALM OIL, PALM KERNEL OIL AND THEIR FRACTIONS AS CONFECTIONERY FATS. Journal of Oil Palm Research, 29(3), 301-310.

6)      Henry, J. (2009). Processing, Manufacturing, Uses and Labelling of Fats in the Food Supply. Annals of Nutrition & Metabolism.

7)      Hinrichsen, N. (2016). Commercially available alternatives to palm oil. Lipid Technology.

            8)      Malaysian Food Regulation 1985

9)      Morris, D., & Vaisey-Genser, M. (2003). Trans Fatty Acids. Encyclopedia of Food Sciences and Nutrition (Second Edition).

10)  Naik, B., & Kumar, V. (2014). Cocoa Butter and Its Alternatives: A Reveiw. JOURNAL OF BIORESOURCE ENGINEERING AND TECHNOLOGY.

11)  Sellami, M., Ghamgui, H., Frikha, F., Gargouri, Y., & Miled, N. (2012). Enzymatic transesterification of palm stearin and olein blends to produce zero-trans margarine fat. Journal of BMC Biotechnology.