Abstract
The authors compare the biological value and safety of hydrogenated fat containing trans-isomers of oleic acid and palm oil-based fat. The chapter assesses the potential of replacing hydrogenated fats by palm oil in the production of special fat products. Hematological and histological studies are carried out in a form of biological experiment on animals (white rats). The study reveals the explicit negative effect of trans-isomers even with a relatively low concentration of trans-isomers in a diet. Pathological changes are not observed in animals when palm-based fat is introduced into their ration. The findings suggest that palm oil along with its fractions may be considered as an alternative to hydrogenated fats in the production of margarine, cooking, baking, and deep-frying fats. The use of palm oil in the production of special fats of increased hardness (spreads. confectionery, waffles and fillings, and chocolate coating) requires the application of modern methods for modifying triglyceride composition of fats – biocatalytic interesterification and fractionation.
TopBackground
For almost 100 years and until very recently, selective hydrogenation has been the most important industrial method of stabilizing vegetable oils and obtaining plastic edible fats for margarine products on their basis. The technology of partial hydrogenation is specifically aimed at increasing the content of trans-isomers in the fat in order to provide necessary ratio between melting point and structural characteristics of the resulting solid hydrogenated fat.
The formation of trans-isomers is associated with a complex of reactions that occur during the partial hydrogenation of vegetable oils (Gassenmeier & Schieberle, 1994; Schmidt, 2000). As a result of the addition of hydrogen to double bonds in molecules of unsaturated fatty acids, the content of polyunsaturated fatty acids (PUFAs) in fat decreases while the content of oleic and stearic acids increases with simultaneous formation of trans- isomers of oleic acid. For this reason, various producers periodically brought fats containing 15% or more trans-isomers to the market (Table 1).
Table 1. Content of trans-isomers in various fats
| Food products | Content of trans-isomers, % |
| Milk fat | 2.3-8.6 |
| Beef fat | 2.0-6.0 |
| Hydrogenated fats | 35.0-67.0 |
| Raw vegetable oils | <0.5 |
| Refined vegetable oils | <1.0 |
| Soft margarines | 0.1-17.0 |
| Cake margarine | 20.0-40.0 |
| Cooking fats | 18.0-46.0 |
| Spreads | 1.5-6.0 |
Source: Kulakova, Viktorova, and Levachev (2008)
Key Terms in this Chapter
Fatty Acid Composition: A composition of fatty acids in mass percentage or molar percentage relative to the amount of fatty acids of the test oil. Fatty acids are carboxylic acids, differ in chain length, the number of double bonds. Some of the fatty acids (only in some oils) contain additional functional groups (for example, ricinol hydroxy acid in castor oil).
Hydrogenated Fat: A fat obtained in technological process hydrogenation.
Hydrogenation: A technological process in which hydrogen gas is added to the double bond in the fatty acid molecule in the presence of special catalysts (most often nickel-based) and the double bond is transformed into a single one. Reducing the number of double bonds lowers the degree of the fatty acid unsaturation, increases its resistance to oxidation by atmospheric oxygen. During hydrogenation, not only double bonds can be converted into single ones, but unsaturated fatty acids in cis-configurations can be partially converted into unsaturated trans-acids.
Palm Oil: A vegetable oil that is solid at room indoor temperature and is extracted from the fruits of tropical palm trees of African origin Elaeis guineensis Jacq.
Interesterification: A technological process in which fatty acid residues are exchanged within molecules and between molecules of triacylglycerols (triglycerides) in the presence of special catalysts. The interesterification is called biocatalytic when the enzyme serves as a catalyst for the process.
Biological Studies: The studies conducted on laboratory animals (most often, on white rats) to determine the effect of certain food components, toxicants, food additives, the mode and duration of feeding experimental animals with experimental diets, on a living organism.
Trans-Isomers of Unsaturated Fatty Acids: The features of the spatial structure of unsaturated fatty acids relative to the double bond plane. If both parts of the fatty acid (before and after the double bond) are located on the same side of the double bond plane, this is the cis-isomer; if on either side of the double bond plane, it is the trans-isomer. Trans-isomers differ from cis-isomers in their biological effects on a body.
Fractionation: A technological process of dividing the original fat into several parts (fractions) differing in their melting point and other characteristics.