Yeast oil as a cocoa butter equivalent

As the fatty acyl distribution of the yeast triacylglycerols shows the same preference as plant oils for the sn-2 position to be occupied by an unsaturated fatty acyl residue (see Ratledge, 1982, 1989b), the attraction of trying to produce a fascimile plant oil from yeasts still remains. Of the 

Cocoa butter has enjoyed a price as high as US 8600/ton in the mid-1980s (Moreton, 1988b Smit et al., 1992) which made it an attractive proposition for several SCO groups to consider as a target. Cocoa butter, however, now (1993) sells at approx. US 3000/tonne which has made it difficult, if not impossible, for these alternative processes to be run economically. Nevertheless, considerable attempts were made in the 1980s to attain a satisfactory cocoa butter equivalent (CBE) yeast oil. The price of a CBE from palm oil fractionation is usually fixed at about 80% of the price of cocoa butter itself and thus a yeast CBE will have to be priced even lower (see section 9.7). 

As an alternative to direct production using yeast technology, there are prospects of producing the correct fatty acyl formulation by transesterify-ing a cheap oil such as mid-palm oil fraction with oleic acid or its various esters including trioleoylglycerol derived from high-oleate sunflower seed oil and an appropriate microbial Upase (see chapter 12 for further details). 

Although this approach was not practical because of the high cost of stearic acid as substrate, this work nevertheless established that there was no a priori reason why yeasts could not be grown with exceptionally high contents of stearic acid. It can be easily calculated that at the growth temperature of yeasts (30°C), the stored fat must have been at least semisolid if not completely solid. The yeast apparently could accommodate 

1 Use of A9 desaturase inhibitors. The first approach was to use a direct inhibitor of the enzyme, sterculic acid cw-9,10-methylene octadecenoic acid, which is found as a natural fatty acid in the seed oil of 

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