Chemical interesterification

The interesterification of fats and oils is the only way to create new hybrid products with new physical, and especially new rheological properties. Chemical interesterification is well known, but has no position or chain specificity, and is not very clean. With lipases in micro-aqueous media, the exchange of acyl groups between the different triglycerides may be oriented, and designed according to the specificity of the enzyme. 

The oxidative stability of the product or margarine basestock obtained from SBO and methyl stearate by chemical interesterification with regioselectivity was evaluated and compared with that of the basestock from which FAs were randomized by H. Konishi et al. (144). 

Rodrigues, J.N., Gioielli, L.A. 2003. Chemical interesterification ofmilkfat and milkfat-corn oil blends. Food Res. Int. 36, 149-159. 

Rousseau, D., Hill, A.R., Marangoni, A.G. 1996a. Restructuring butterfat through blending and chemical interesterification. 1. Melting behavior and triacylglycerol modifications. J. Am. Oil Chem. Soc. 73, 963-972. 

Chemical interesterification randomizes the fatty acid distribution in the triacylglycerol. The extent of modification of the fat depends on the composition of the starting fat and whether a single or a blend of fats is used and the conditions of the chemical interesterification process (Mickle et al., 1963 Huyghebaert et al., 1986 Rousseau and Marangoni, 2002). 

A reduced level of low molecular weight monounsaturated triacylglycerols (C36 and C38) and increased levels of trisaturated triacylglycerols (C44-C50) was obtained on undirected chemical interesterification of milk fat with sodium methoxide (0.5%) as catalyst, resulting in a wider temperature range for crystallization compared to native milk fat (Parviainen et al., 1986). 

Figure 8.8. Effect of chemical interesterification on the relative proportion (w/w) of milk fat triacylglycerols as a function of carbon number (CN). TAG = triacylglycerol. Noninteresterified milk fat (O-O), interesterified milk fat-15 min ( - ), 30 min ( - ), 60 min ( - ), 90 min (A-A), and 120 min (A-A)- (Reproduced with permission from Rousseau et al., 1996a).

Rousseau et al. (1996a, b) examined the properties of physical blends and those of blends obtained on chemical esterification of milk fat-canola oil blends (using 0.5% methoxide, 78-82°C for 15-120 min). For milk fat-canola oil blends containing >20%, w/w, canola oil, chemical interesterification reduced the solid fat content of all blends (Rousseau et al., 1996a). For non-interesterilied and interesterified blends, hardness decreased with increasing content of canola oil. 

Although the processes of hydrogenation and chemical interesterification that are commonly used in the wider oils and fats industry may be applied to milk fat, there are a number of factors that prevent these being an attractive option for milk fat modification. Apart from the fact that ingredient manufacturers are seeking alternatives to the use of chemicals, milk fat is... 

When a 1,3-specific lipase is used for interesterification, the enzymatically-modified product has some different properties compared to those of a chemically-interesterified product. For example, the dropping point of butterfat was increased slightly by chemical interesterification whereas interesterification by a 1,3-lipase from Rhizopus arrhizus led to a 2-4°C decrease in dropping point. Although both methods of interesterification reduced hardness, the magnitude of the effect was greater for the enzymatically-interesterified fat (Marangoni and Rousseau, 1998). 

When 80 20 blends of butter fat and canola oil were used, chemical interesterification increased the solid fat content above 10°C while enzymatic interesterification by Rhizopus arrhizus lipase reduced solid fat content over the range 5 40 C (Rousseau and Marangoni, 1999). 

Fig. 34.27. Semi-continuous (chemical) interesterification line with postbleaching. (Courtesy of Desmet Ballestra Oils and Fats, Brussels, Belgium.)...

Differences in microstructure between 20%SSS/80%000 can be observed upon interesterification (Figure 17.8). Chemical interesterification caused a severe decrease in the melting point of the system as no crystals were observed above 30°C. Chemical interesterification also caused an increase in nucleation rate with a concomitant... 

Marangoni, A.G., and Rousseau, D. (1998). The influence of chemical interesterification on the physicochemical properties of complex fat systems. 3. Rheology and fractality of the crystal network. Journal of American Oil Chemists Society. 75 1633-1636. 

Lipase catalyzed reactions take place in the neat oil or in a nonpolar (usually hydrocarbon) solvent. The efficiency depends on the amount of water, solvent (if present), temperature, and ratio of reactants. A factorial approach can be used to optimize the conditions (32). In interesterification reactions, 1,3-specific enzymes give control over product composition that is not possible using chemical catalysts. For example, starting with SOS and OOO, chemical interesterification produces aU eight possible isomers (see Table 5). Enzymatic interesterification does not exchange fatty acids at the sn-2 position, and it will result in only two additional molecular species, OOS and SOO. In more realistic situations, chemical and enzymatic interesterification may produce the same or a similar number of molecular species, but in different proportions (31). 

Chemical interesterification is used in the production of caprenin, salatrim, and olestra. 

Chemical interesterification would lead to randomization of all of the acyl chains, and the products would have different melting behavior from that required by a cocoa butter equivalent (188). 

Two basic types of chemical interesterification are practiced random and directed. Both involve the use of transition metals, such as sodium, or more commonly derivatives, such as sodium methoxide, as a catalyst. The differences between these two interesterification reactions are summarized in Table 22. 

Chemical interesterification is conveniently achieved by using alkali metal methylates as a catalyst. Microbial lipases are also used as biocatalysts in enzymatic interesteiification. In contrast to the chemical process, the enzymatic process can be more selective if an enzyme with positional specificity is used, but this reaction is usually much slower and more sensitive to reaction conditions. Recent developments in lipase-catalyzed interesterification have resulted in new industrial applications of this process (255). Nevertheless, the high costs of enzymes and process equipment may limit widespread adoption of this process. 

Studies have been pubhshed on chemical interesterification of tallow with regular sunflower oil (96-98). Changes in the proportion of sunflower oil in blends with tallow produce httle modification of the solid content or the melting point. However, important modifications take place in the thermal properties of these blends when they are subjected to a process of chemical interesterification. In addition, modifications occur in the crystalline structure. Solid beef tallow—composed... 

Chemical interesterification results in a complete randomization of acyl groups in the TAGs. Interesterification, alone or in combination with other processes, extends... 

Two mechanisms have been proposed for alkaline-catalyzed chemical interesterification enolate anion formation and carbonyl addition. 

Two basic types of chemical interesterification processes involving the use of metal catalysts are employed random and directed. 

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