Cocoa triacylglycerol

Figure 26.2 shows the structures of two typical triacylglycerols, 2-oleyl-l,3-distearylglycerol (Figure 26.2a) and tristearin (Figure 26.2b). Both occur naturally—in cocoa butter, for example. All three acyl groups in tristearin are stearyl (octadecanoyl) groups. In 2-oleyl-l,3-distearylglycerol, two of the acyl groups are stearyl, but the one...

Cocoa butters have a natural variation in physical properties related to the triacylglycerol structure Malaysian, Indian and Indonesian butters are harder than those from Africa, and Brazilian butters are the softest. The hardness of typical butters from some continents has changed over the years (Timms and Stewart, 1999). Because the hardness affects the processing required for chocolate manufacture, suppliers of cocoa butter to that trade blend butters to attempt to produce a uniform product. 

Triacylglycerols are the most important components of both cocoa butter and CBAs. In cocoa butter they are responsible for the characteristic rapid... 

Tables have been published describing ranges of the major triacylglycerols in cocoa butter, CBAs and fats used in the manufacture of CBAs (Chaudhuri el al., 1983 Shukla etal., 1983 Podlaha etal., 1984,1985 Rezanka and Mares, 1991 Ruiz Mendez and Huesa Lope, 1991 Wong Soon, 1991 Blicher-Mathiesen, 1994 Shukla, 1995,1997 Lipp and Anklam, 1998a).

Triacylglycerols in cocoa butters have been separated by high performance liquid chromatography (HPLC) or gas chromatography (GC). These methods... 

No comprehensive comparison has been made of the proportions of the free and esterified sterols in cocoa butter with those of fats likely to be used in cocoa butter adulteration. However Gordon and Griffiths (1992) examined the sterol esters of palm kernel oil by isolation with TLC followed by GC and HPLC. They pointed out the problem of co-elution of triacylglycerols with steryl esters with GC. The characterization of esters of triterpene alcohols in CBA fats might well prove useful where the use of fats containing shea is suspected. 

The advent of relatively inexpensive computers has enabled the accumulation and rapid analysis of large sets of data. By this means patterns and trends not always apparent from visual inspection of chromatograms or tables of data can be discriminated by being sorted into recognizable patterns. This approach is essential for some techniques such as pyrolysis where the quantity of data produced would otherwise be overwhelming. Several statistical approaches to exploit the information content of fatty acid and triacylglycerol patterns for the detection and quantification of CBEs in cocoa butter have been reported (Lipp et al., 2001 Simoneau et al., 1999). 

Discriminant analysis has been used in many of the analyses described in this chapter, in particular the classification of cocoa butters by origin and processing from pyrolysis MS data (Radovic et al., 1998), from triacylglycerol profiles obtained by HPLC (Hernandez et al., 1991) and from analysis of volatiles (Pino, 1992). Data from the analysis of mixtures of CBEs with cocoa butter, which model techniques for measuring CBEs in chocolate, have been treated by similar means (Anklam et al., 1996). 

Neri, A., Simonetti, M.S., Cossignani, L. and Damiani, P. (1998) Identification of cocoabutter equivalents added to cocoa butter-I. An approach by fatty acid composition of the triacylglycerol sub-fractions separated by Ag+-HPLC. Z. Lebensm. Unters. Forsch. A., 206(6), 387-392. 

Takagi, T. and Ando, Y. (1995) Stereospecific analysis of monounsaturated triacylglycerols in cocoa... 

When interesterification of milk fat was carried out at 100°C with 0.2% sodium, there was an increase in middle-melting point triacylglycerols but only small effects on the melting properties of milk fat (Timms and Parekh, 1980). These authors concluded that although the interesterified milk fat was more compatible with cocoa butter than unmodified milk fat, the effects were not sufficient to warrant the use of interesterification (Timms and Parekh, 1980). 

The possibility of CB fractionation with supercritical carbon dioxide (SC-C02) has not yet been fully explored. Coenen Kriegel [7] claimed that fats can be fractionated using SC-C02 without giving examples. Rossi et al. [8] only observed minor changes in the triacylglycerol compositions of fats extracted from cocoa nibs and shells as a function of time, temperature and pressure. A real fractionation of the fat, however, was not achieved. 

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. 

Kokum (Garcinia indica). Both kokum and mahua fats are rich in saturated and oleic acid and contain high levels of SOS triacylglycerols. They can be fractioned separately or as blends of the two oils to produce stearins that can be used as cocoa butter extenders (Table 8) (125). Kokum butter is one of six permitted fats (pahn oil, illipe butter, kokum butter, sal fat, shea butter, and mango kernel fat), which, in some countries at least, can partially replace cocoa butter in chocolate (90). 

Most of the flavor compounds in fats and oils are produced by the reaction of oxygen with unsaturated fatty acids in triacylglycerols or polar lipids. On the other hand, some flavor compounds such as those present in cocoa butter, roasted sesame oil, or roasted peanut oil are generated by the interaction of reducing sugars with amino compounds during thermal processing. 

The total fat content of the whole bean on a dry basis is around 48 9%, and triacylglycerol is the major storage component. A mature cocoa bean can store up to 700 mg of cocoa butter. As a tree may produce as many as 2000 seeds a year, a single tree could yield up to 15 kg of cocoa butter annually. 

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 fatty acid composition, various analytical constants, and triacylglycerol composition of different cocoa butters are presented in Tables 1-3, respectively. These results show that Malaysian cocoa butter contains the highest levels of mono-unsaturated triacylglycerols. The Brazihan cocoa butter contains the lowest levels of monounsaturated triacylglycerols and the highest levels of other unsaturated triacylglycerols. The cocoa butters from India and Sri Lanka are close to Malaysian cocoa butter in terms of hardness and triacylglycerol composition. 

There is a good correlation between the triacylglycerol composition and solid fat content of these cocoa butters. Malaysian, Sri Lankan, and Indian cocoa butters are the hardest, and Brazilian is the softest, whereas others lie in between. The quality of the Brazilian cocoa butter can be unproved by mixing it with Malaysian cocoa butter, which will result in higher solid fat content at various temperatures. 

The solid fat components form eutectics with the triacylglycerols of cocoa butter. 

This category offers a range of confectionery fats with different levels of physical properties, but all having triacylglycerol compositions that make them incompatible with cocoa butter i.e. they are aU used in formulations with cocoa powder, mainly for compound coating. 

---