The Chemistry of Oils and Fats

Fats are chemically triglycerides and can be regarded as the esters produced by the reaction of fatty acids with the trihydric alcohol glycerol. In practice, oils and fats are the product of biosynthesis. Some sugar confectionery contains oils or fats whereas other products, e.g. boiled sweets, are essentially fat-free. The traditional fat used in sugar confectionery is milk fat, either in the form of butter, cream, whole milk powder or condensed milk. Milk fat can only be altered by fractionating it. and while this is perfectly possible technically, there must be sufficient commercial and technical benefits to make it worthwhile. One problem with fractionation operations is that both the desirable and the undesirable fractions have to be used. 

Whereas vegetable fats were used originally as a cheaper substitute for milk fat, the ability to specify the properties of vegetable fat has 

Some fats go into confectionery as a component of other ingredients. The common example is nuts, which contain fats often of types such as lauric acid in addition to unsaturated fats. These fats are sometimes the origin of spoilage problems (see also page 22). 

Fatty acids consist of a hydrocarbon chain with a carboxylic acid at one end. They can be classified on the basis of the length of the hydrocarbon chain (Table 2.2) and whether there are any double bonds. Trivial names of fatty acids such as butyric, lauric, oleic and palmitic acids are in common use in the food industry. A form of short-hand is used to refer to triglycerides where POS is palmitic, oleic, stearic. If the chain length is the same an unsaturated fat will always have a lower melting point. Another classification of fats that is used is in terms of the degree of unsaturation of the fatty acids. Saturated fats are fats without any double bonds. Many animal fats are saturated, but some vegetable fats, e.g. coconut oil, are saturated also. Mono-unsaturated fats include oils like olive oil but also some partially hydrogenated fats. Polyunsaturated fats have many double bonds and include sunflower oil. Because they are 

Apart from specifications as to origin, e.g. palm kernel oil, fats are normally supplied on the basis of established parameters. One of these is the iodine value. This reflects the tendency of iodine to react with double bonds. Thus the higher the iodine value the more saturated the fat is. An iodine value of 86 approximates to one double bond per chain, whereas an iodine value of 172 approximates to two double bonds per chain. Another parameter is the peroxide value. This attempts to measure the susceptibility of the fat or oil to free radical oxidation. The test is applied on a freshly produced oil and measures the hydroperoxides present. These 

Fats are, chemically, triglycerides and can be regarded as the esters produced by the reaction of fatty acids with the trihydric alcohol 

Chain length C=C bonds Name Butter fat Palm oil Coconut oil 

A useful convention is to denote fatty acids by the number of carbon atoms and the number of C=C bonds. For example, lauric acid, which has 12 carbon atoms and no C=C bonds, is C12 0. This nomenclature does not specify the position of the C=C bonds, nor whether they are cis or trans. All fats are mixtures of triglycerides (and hence contain a number of different fatty acid residues). The approximate fatty acid composition of some fats is shown in Table 3.4. Butterfat contains a much wider range of fatty acids than the vegetable fats. Coconut oil contains very high levels of saturated fatty acids, particularly lauric acid. 

Good quality ice cream can only be made with fats that have a suitable melting profile. Fats that melt at high temperatures produce ice cream with a waxy mouth-feel. Conversely, it is difficult to create stable foams with fats that melt at low temperatures, for reasons that are discussed in Chapters 4 and 7. Dairy fat has the right melting profile to 

Water forms a high proportion of ice cream (typically 60-72% w/w) and water ice mixes (typically 75-85%). Water is the medium in which all of the ingredients are either dissolved or dispersed. During freezing and hardening the majority of the water is converted into ice. 

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Gunstone, F. (2004), The Chemistry of Oils and Fats Sources, Composition, Properties and Uses, Blackwell, Oxford, UK. 

Sources Gunstone, F.D., The Chemistry of Oils and Fats—Sources, Composition, Properties and Uses, CRC Press, Boca Raton, FL, p. 7, 2004 FSA (Food Standards Agency), Fats and oils, McCance and Widdowson s the Composition of Foods, 5th edn. Royal Society of Chemistry, Cambridge, U.K., 1991 Altar, T., More than you wanted to know about fats/oils, Sundance Natural Foods, 1995, Available at http //www.efn.org/ sundance/fats and oils.html (accessed 20/2/2008). 

Sources Gunstone, F.D., The Chemistry of Oils and Fats—Sources, Composition, Properties and Uses, CRC Press, Boca Raton, FL, p. 7, 2004 Wikipedia, Fat, 2007, Available at http //en.wikipedia.org/wiki/Fat (accessed 20/2/2008). 

Antioxidants play an important role in the deceleration of lipid oxidation reactions in foodstuffs. According to FDA they are defined as substances used as preservatives, with the aim to reduce spoilage, rancidity or food discoloration, which are derived from oxidations. Addition of antioxidants in foodstuffs is either intentional (direct addition into product) or symptomatic (migration of antioxidants from packaging material into product). The right and effective use of antioxidants depends on the understanding of (a) the chemistry of oils and fats, and (b) the mechanism of oxidation and their operation as substances, which result in food oxidation (Table 13.12). ... 

Hyphenated TLC techniques. TLC has been coupled with other instrumental techniques to aid in the detection, qualitative identification and, occasionally, quantitation of separated samples, and these include the coupling of TLC with high-pressure liquid chromatography (HPLC/TLC), with Fourier transform infra-red (TLC/FTIR), with mass spectrometry (TLC/ MS), with nuclear magnetic resonance (TLC/NMR) and with Raman spectroscopy (TLC/RS). These techniques have been extensively reviewed by Busch (1996) and by Somsen, Morden and Wilson (1995). The chemistry of oils and fats and their TLC separation has been so well established that they seldom necessitate the use of these coupling techniques for their identification, although these techniques have been used for phospholipid detection. Kushi and Handa (1985) have used TLC in combination with secondary ion mass spectrometry for the analysis of lipids. Fast atom bombardment (FAB) has been used to detect the molecular species of phosphatidylcholine on silica based on the molecular ion obtained by mass spectrometry (Busch et al, 1990). 

The industrial chemistry of oils and fats is a mature technology, with decades of experience and rehnement behind current practices. It is not, however, static. Environmental pressures demand cleaner processes, and there is a market for new products. Current developments are in three areas green chemistry, using cleaner processes, less energy, and renewable resources enzyme catalyzed reactions, used both as environmentally friendly processes and to produce tailor-made products and novel chemistry to functionalize the carbon chain, leading to new... 

Alcohol sulfates were first obtained either by the reaction of olefins with sulfuric acid or by sulfation of alcohols produced by hydrogenolysis of oils and fats with sulfuric acid. With the advent of petrochemistry and the progress of chemistry and chemical engineering, alcohol sulfates and their derivatives have become one of the most important surfactants and are produced in large amounts using techniques different from those originally used. They are based on a wide range of alcohols and have found applications in almost all domestic and industrial sectors. 

A series which presents the current state of the art in chosen areas of oils and fats chemistry, including its relevance to the food and pharmaceutical industries. Written at professional and reference level, it is directed at chemists and technologists working in oils and fats processing, the food industry, the oleo-chemicals industry and the pharmaceutical industry, at analytical chemists and quality assurance personnel, and at lipid chemists in academic research laboratories. Each volume in the series provides an accessible source of information on the science and technology of a particular area. 

Prentice, J.H. (1969) The milk fat globule membrane 1955-1968. Dairy Sci. Abstr., 31, 353-6, Richardson, T, and Korycka-Dahl, M. (1983) Lipid oxidation, in Developments in Dairy Chemistry, Voi. 2 Lipids, (ed. P.F. Fox), Applied Science Publishers, London, pp. 241-363, Rossell, J.B. (1986) Classical analysis of oils and fats, in Analysis of Oils and Fats, (eds R.J. 

Michel-Eugene ChevreuI, 1786-1889. French chemist and psychologist who made notable contributions to the chemistry of fats and oils, soap, candles, and dyes. He lived to be almost one hundred and three years old, sound and active in mind and body. When he investigated Hatchett s artificial tanning agents, ChevreuI was only twenty-four years old (twenty-one years younger than Hatchett). See refs. (48, 49, and 52). 

IUPAC, Standard Methods for the Analysis of Oil, Fats and Derivatives, International Union of Pure and Applied Chemistry, Blackwell Scientific Publications, Oxford, UK, 1987. 

IUPAC (International Union of Pure and Applied Chemistry). 1987a. Method 2.501. Determination of the peroxide value (P.V.). In Standard Methods for the Analysis of Oils, Fats and Derivatives, 7th ed. (C. Paquot and A. Hautfenne, eds.) pp. 199-200. Blackwell Scientific, Palo Alto, Calif. 

G. Hoffmann, in The Chemistry and Technology of Edible Oils and Fats and Their High-Fat Products, Academic Press, London, p. 203 (1989). 

Mottram, H.R. (1999) The Application of HPLC-APCI MS to the Regiospecific Analysis of Triacylglycerols in Edible Oils and Fats. PhD thesis, Department of Chemistry, University of Bristol, UK. Movia, E. and Remoli, S. (1977) Application of enzymic hydrolysis to determine the genuineness of butter., Bollettino dei Chimici dei Laboratori Provinciali, 3, 187-192. 

The part of chemistry dealing with oils and fats is commonly known as oleochem-istry. Figure 2.2.6 gives an overview of typical processes and products. 

The main organizations that develop or validate methods for fats and oil analysis include International Union for Pure and Applied Chemistry (lUPAC), International Oiganization for Standardization (ISO), Association of Official Analytical Chemists (AOAC), American Oil Chemists Society (AOCS), American Society for Testing and Materials (ASTM), Association Francaise de Normalization (AFNOR), British Standards Institution (BSI), Deustsches Institute fur Normung (DIN), and the Federation of Oils, Seeds and Fats Association (FOSFA). In addition, there is an increasing trend for the various national standard institutions to develop their own standard methods based on the standard ISO methods these are generally adopted as official methods. 

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