Interesterified Fat

Interesterified fats are less liable to rancidity and are oils such as soybean oil that are chemically modified to make their consistency more solid. These oils are more stable and can be effectively used in applications such as deep frying. In the interesterification process to a polyunsaturated fat, one or more polyunsaturated fatty acids are esterified to a glycerol backbone. Some research indicate that interesterification process that is used as an alternative to partial hydrogenation process (which yields trans fats) may pose even a higher health risk than trans fats.

Stearic acid (a saturated fatty acid) is used to replace polyunsaturated fatty acid in the interesterification process.

This process can be induced by enzymatic crystals or chemicals and can be applied to hydrogenated or fractionated oils and natural oils or fats. The end product of interesterification can be different than the natural oils, but it does not introduce trans fatty acids. Controlled crystallization method can separate interesterified fats. Polyunsaturated fatty acid in polyunsaturated fat is usually found in the middle position on the glycerol (sn2), but stearic acid is not found usually in that position in vegetable oils that are used in human diets.

Hydrogenation process hardens oils to get margarine and shortening, while interesterification process blends soft oils with hard fats to get a desired consistency and functionality. For example stearin (a hard fraction) blended with palm oil (soft oil) is one option for interesterified goods.

Unlike other saturated fats, stearic acid is not linked with elevation of low density lipoproteins (LDL) in the body. However scientific researches have raised a concern about interesterified fat consumption. Replacing polyunsaturated fatty acid molecule with stearic acid in any vegetable oil may pose a health risk as the resultant fat is not easily metabolized, if stearic acid is place in the middle fatty acid position of a fat molecule. Other researches also show that interesterified fat may lower the high density lipoprotein (HDL) levels that is the good cholesterol and may raise the blood sugar levels.

Recently food and drug administration (FDA) has issued important labeling clarification, where interesterified fats should be appropriately labeled as ‘interesterified soybean oil’ or ‘stearate high’ or ‘stearate rich’ if the proportion of stearate is greater than 20%. This regulation by FDA will allow the oil companies to replace the term ‘hydrogenated’ with ‘interesterified’ where declaring the finished products ingredients will be a compulsion.
The most applied interesterification process is chemical or random interesterification as it is easier and cheaper compared to enzymatic or directed interesterification.

Submitted on January 16, 2014