Palmitic acid cocoa

Some plants produce a mixture of fatty acids (Table 11.3). The fat in seeds of the cacao tree (Theobroma cacao) contains a mixture of stearic and palmitic acids. The fat is known as cocoa butter from its resemblance to the butter produced from cow s milk (see Box 11.2). 

Table 8.10 Masses observed in the various fragment spectra of the three deprotonated molecular ions present in the DCI spectrum of natural cocoa butter (P = palmitic acid,...

Unlike many fats and oils, the cocoa butter used to make chocolate is remarkably uniform in composition. All triacylglycerols contain oleic acid esterified to the 2° OH group of glycerol, and either palmitic acid or stearic acid esterified to the 1 ° OH groups. Draw the structures of two possible triacylglycerols that compose cocoa butter. 

Unilever developed a method for upgrading palm mid-fraction (PMF) as a cocoa butter equivalent. The PMF is too rich in palmitic acid and has too little stearic acid, but this deficiency can be repaired by enzyme-catalysed acidolysis with stearic acid. Reaction is confined to the exchange of palmitic acid by stearic acid at the sn-1 and 3 positions with no movement of oleic acid from the sn-2 position. A similar product is produced enzymatically by acidolysis of high-oleic sunflower oil (rich in triolein) and stearic acid. 

Cocoa butter is the most expensive constituent of chocolate formulations as well as an extremely important component. It is composed predominantly (>75%) of symmetrical triacylglycerols with oleic acid in the 2-position (1). Approximately 20% of triacylglycerols are hquid at room temperature, and cocoa butter has a melting range of 32-35°C and softens around 30-32°C. This is essential to the functionahty of cocoa butter in its applications. It contains only trace amounts of the unsymmetrical triacylglycerols (PPO, PSO, and SSO). (P = palmitic acid, O = oleic acid, and S = stearic acid the order of letters indicates the position of the acids in the triacylglycerols molecule.)... 

The employment of 1,3-selective lipases leads to structured TAG where specific acyl groups are confined to either the l-(3-) or 2-acylglycerol position. One of the earliest examples is cocoa butter substitute formed by 1,3-selective lipase-catalyzed acidolysis (reaction 1 of Fig. 3) of palm oil midfraction by palmitic acid (resulting in the replacement of 1-, 3-dipalmityl, 2-oleyl TAG by l-(3-) palmityl, 2-oleyl, 3- (1-) steryl TAG and 1-, 3-disteryl, 2-oleyl TAG, both of which are abundant in cocoa butter). The product... 

Ccxjoa butter is the triglyceride which derives from cocoa beans it is composed of a large amount of palmitic acid on the glyceral backbone. Because of the high saturation, cocoa butter is a solid and exhibits a rather sharp melting point at about body temperature which incidentally, is partially responsible for the pleasant texture of high quality chocolates. 

Cocoa butter (CB) is a highly valued ingredient primarily used in the confectionery industry due to its specific physical and chemical properties. CB is solid at room temperature (below 25 °C), and liquid at body temperature (—37 °C) [43], Furthermore, the predominant presence of symmetrical TAG, about 90 % of the TAG species in CB, is mainly responsible for the functionality of this fat [44], The major FAs of cocoa butter are palmitic acid (Cl6) 25-33.7 %, stearic acid (C18 0) 33.7-40.2 %, oleic acid (C18 l) 26.3-35 % and linoleic acid... 

One of the most abundant SFA in many common foods (dairy, meat, palm and coconut oil) is palmitic acid (PA, 16 0). The amoimt of PA is the highest in palm oil (around 50%), but significant amounts of PA (25-26%) can also be foimd in butter, chicken fat, lard, beef and lamb fat, as well as in cocoa butter. Even olive oil, which is one of basic components of the healthy Mediterranean diet contains around 16% of PA [6]. Fiulhermore, PA is present in human milk with 20-25% of total fats. Overall, PA and stearic acid (18 0) are the most common dietary SFA and therefore they are also the major SFA in hiunan plasma and tissues. Their concentration in serum/plasma phospholipids and cholesterol esters reflect dietary high fat intake. 

Stearic add n-octadecanoic add, CH3-(CH2)](-COOH, a fatty acid, M, 284.5, m.p. 71.5°C, b.p.,5 232°C. Together with palmitic acid, S.a. is one of the most plentiful and most widely distributed fatty acids, occurring esterified in practically all animal and plant oils and fats, e.g. 34% in cocoa butter, 30% in mutton fat, 18% in beef fat, 5-15% in milk fat. It is used in the manufacture of candles, soaps, detergent antifoams, pharmaceuticals and cosmetics. Stearin is the triacylglycerol of S. a. 

Although, in general, fats come from animal sources and oils come from vegetable sources, this is not always so. For example, fish oils are high in unsaturated fatty acids. The unsaturated fatty acid contents of sardine oil and cod-liver oil are 77% and 84%, respectively. Likewise, not all fats come from animal sources. Cocoa butter (see opening photo), with a fatty acid composition of 24% palmitic acid and 35% stearic acid, is a solid at room temperature. 

Cocoa butter is a unique, simple fat containing mainly mono-unsaturated and di-unsaturated glycerides. It has a typical composition of 26% palmitic acid (16 0), 36% stearic acid (18 0), 33% oleic acid (18 1) and 3% linoleic acid (18 2), although there are slight variations in composition... 

Fuji Oil (Matsuo et al, 1981) filed the first patents for the lipase-catalysed synthesis of a cocoa butter equivalent from palm oil and stearic acid. Both companies currently manufacture it using 1,3-selective lipases to replace palmitic acid with stearic acid at the 5n-l and sn-2> positions. The reactions usually performed are transesterification or acidolysis of cheap oils using tristearin or stearic acid as the acyl donors and a 1,3-specific lipase (Figure 3). Suitable starting oils besides palm oil mid-fractions are sunflower, rapeseed (Adlercreutz, 1994) and olive (Chang et al, 1990) oils. 

Figure 3. Possible approaches to the synthesis of cocoa butter equivalents (A), addolysis of palm oil mid-fractions with stearic add (B), interesterification between palm oil mid-fractions and stearic acid esters (C), addolysis of palm oil mid-fractions with mixtures of stearic and palmitic acid (D), interesterification between palm oil mid-fractions and stearic and palmitic acid esters. Ol, oleic add. Pa, palmitic acid. St, stearic acid. X, alcohol.

The major fatty acids present in cocoa butter triglycerides are palmitic acid (P), oleic acid (O), and stearic acid (S). Cocoa butter is composed mainly of symmetrical triglycerides (>75%) with oleic acid in the sn-2 position (POP, POS, SOS) and with trace amounts of asymmetrical triglycerides (PPO, PSO, and SSO) (Shukla, 1995 van Malssen et al., 1996). This natural fat is relatively simple insofar as it is composed of a small number of TAG components and melts over a narrow temperature range, which is important in terms of textural quality (Shukla, 1995). The typical composition of cocoa butter is shown in Table 1. 

The conversion of inexpensive palm oil fraction into a cocoa butter substitute requires partial replacement of palmitic acid by stearic acid in the l(3)-position while leaving the 2-position luiaffected. This was accomplished by transesterihcation of a mixture of stearic acid and a palm oil fraction using a l(3)-specihc lipase as a catalyst. The reaction was found to take place at the interface and the interfacial area was rate limiting. 

Cocoa butter is composed mainly of glycerides of stearic, palmitic, and oleic fatty acids (see Eats AND FATTY oils). The triglyceride stmcture of cocoa butter has been determined (11,12) and is as foUows ... 

Cocoa seeds contain 35-50% of oil (cocoa butter or theobroma oil), 1-4% theobromine and 0.2-0.5% caffeine, plus tannins and volatile oils. During fermentation and roasting, most of the theobromine from the kernel passes into the husk, which thus provides a convenient source of the alkaloid. Theobroma oil or cocoa butter is obtained by hot expression from the ground seeds as a whitish solid with a mild chocolate taste. It is a valuable formulation aid in pharmacy where it is used as a suppository base. It contains glycerides of oleic (35%), stearic (35%), palmitic (26%), and linoleic (3%) acids (see page 44). 

More than 300 compounds had been identified in cocoa volatiles, 10% of which were carbonyl compounds (59,60). Acetaldehyde, 2-methylpropanal, 3-methylbutanal, 2-methylbutanal, phenylacetaldhyde and propanal were products of Strecker degradation of alanine, valine, leucine, isoleucine, phenyl-acetaldehyde, and a-aminobutyric acid, respectively. Eckey (61) reported that raw cocoa beans contain about 50-55% fats, which consisted of palmitic (26.2%), stearic (34.4%), oleic (37.3%), and linoleic (2.1%) acids. During roasting cocoa beans these acids were oxidized and the following carbonyl compounds might be produced - oleic 2-propenal, butanal, valeraldehyde, hexanal, heptanal, octanal, nonanal, decanal, and 2-alkenals of Cg to C-q. Linoleic ethanal, propanal, pentanal, hexanal, 2-alkenals of to C q, 2,4-alkadienals of Cg to C-q, methyl ethyl ketone and hexen-1,6-dial. Carbonyl compounds play a major role in the formation of cocoa flavor components. 

---