Modification of Oils and Fats

The enzymes used for modification of oils and fats are extraoelluar microbial lipases. They are excreted by micro-organisms into the growth medium to catalyse the degradation of lipids, and can be produced on a large scale by fermentation. 

Macrae, A.R. (1985b) Enzyme-catalysed modification of oils and fats. Philos. Trans. R. Soc. London B310, 227-233. 

The food industry is a traditional market for enzymes with the frequent discovery of new enzymes applications. Pazczola (2001) provided a comprehensive review on the latest enzyme applications in the food industry. Lipase-catalyzed modifications of oils and fats, including lipase-catalyzed production of margarine, coco butter equivalents and structured lipids, represent some of those technologies that have been industrialized (Xu, 2004a). 

Mixtures of triglycerides, triglycerides plus free fatty adds or triglycerides plus fatty acid alkyl esters are used as reactants in fat modification processes. These mixtures are exposed to lipases supported on macroporous particles in the presence of a small amount of water. Liquid substrates (oils) can be reacted without use of a solvent, but with solid reactants (fats) it is necessary to add a solvent to ensure that the reactants and products are completely dissolved in the organic phase. Various water immisdble solvents can be used, but hexane is preferred for commercial operation because this solvent is already used industrially for the processing of oils and fats. 

The modification processes which will be described are hydrogenation, fractionation and interesterification. These processes are used to widen the applicability of oils and fats and also, in the case of hydrogenation, to make products of acceptable oxidative and flavour stability from unstable or relatively unstable raw materials. 

IODINE VALUE. As this is a constant of considerable importance in the analysis of oils and fats, numerous methods and modifications have been devised for its determination. As variations in the iodine value are obtained by different methods, the one used should always be stated and the conditions laid down by the particular method should be strictly adhered to. 

The test is somewhat cumbersome and can be found in all standard works on the examination of oils and fats, but the modification by Hawley of the method of Fritzsche, using digitonin, for routine examination of butter fats with border-line Reichert-Meissl values, considerably shortens the time and reduces the amount of material required and the manipulations involved. The method appears to be based on sound principles and sufficient practical detail is given in the original paper to ensure that it can be followed with ease. The procedure is ... 

In addition to having the required spedfidty, lipases employed as catalysts for modification of triglycerides must be stable and active under the reaction conditions used. Lipases are usually attached to supports (ie they are immobilised). Catalyst activity and stability depend, therefore, not only on the lipase, but also the support used for its immobilisation. Interesterification reactions are generally run at temperatures up to 70°C with low water availability. Fortunately many immobilised lipases are active and resistant to heat inactivation under conditions of low water availability, but they can be susceptible to inactivation by minor components in oils and fats. If possible, lipases resistant to this type of poisoning should be selected for commercial operations. 

Biodiesel (fatty acid methyl ester (FAME)) production is based on transesterification of vegetable oils and fats through the addition of methanol (or other alcohols) and a catalyst, giving glycerol as a by-product (which can be used for cosmetics, medicines and food). Oil-seed crops include rapeseeds, sunflower seeds, soy beans and palm oil seeds, from which the oil is extracted chemically or mechanically. Biodiesel can be used in 5%-20% blends with conventional diesel, or even in pure form, which requires slight modifications in the vehicle. 

Physical modification of milk fat by fractionating milk fat or by blending milk fat or milk fat fractions with other oils and fats results in products with an altered triacylglycerol composition, but one in which the fatty acids in milk fat maintain their original position in the triacylglycerol molecules (Kaylegian, 1999). 

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... 

The substrate spedfidties of lipases are crudal to their application as catalysts for modification of triglycerides. The enzymes can show spedfidty with respect to both the fatty add and glycerol parts of triglycerides. However, most extracelluar microbial lipases are not hi y specific with respect to the fatty add groups found in the oils and fats used as raw materials for the edible fats industry, although reaction rates can vary wifii the chain length, and extent and position of unsaturation of the fatty add group. 

One of the areas in which immobilized enzymes are expected to have major impact is in the biocatalysis of reactions in organic media, for example, in the synthesis of chiral compounds as intermediates in the manufacture of pharmaceuticals and in the modification of naturally occurring fats and oils to produce value-added products targeted at the nutraceuticals market. 

Some representative points and comments (repeals, modifications, and amendments) of the direc-tive/regulations for oils and fats are given in Table 5.7. 

Modern biobased lubricants are mainly based on rapeseed oil, sunflower oil, soybean oil, and animal fats. These oils easily undergo oxidation due to their content of polyunsaturated fatty acids such as linoleic acid and linolenic acid. Efforts have been made to modify the oils to provide a more stable material and a product more competitive in performance to mineral oil-based lubricants. This modification can involve partial hydrogenation of oil and a shifting of its fatty acids to high oleic acid content [21]. Other reported changes that address the problem of unsaturation include alkylation, acylation, hydroformylation, hydrogenation, oligomerization (polymerization), and epoxidation [20, 22]. 

Syndet bars are nonsoap-based materials and their active ingredients can be of widely different types. They can be derived from both natural oils and fats through chemical modification of their fatty acids, or the petrochemical industry. 

In addition to hydrolysis, lipases can also catalyze transesterilication and inter-esterfications. This diversity allows lipases to be used for various applications in the field of chemical synthesis, including oil and fat splitting and modification. Details of lipase nse in various applications are provided in Section 2.6. 

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