Soapy flavours

Lipases release free fatty acids from milk lipids to generate a rancid, butyric, cheesy, fatty, soapy flavour. Most important are the even numbered acids C4 to C20. In cheeses from goats and sheep 4-methyl octanoic acid imparts a strong animal, goaty character. 

Lipases in stored butter gradually release fatty acids from tri-acylglycerols, and their presence can be detected as a rancid and soapy flavour when they reach 30-40% of their threshold concentrations, which is a result of their synergism. The reaction is called hydrolytic rancidity. Responsibe for the rancid flavour is mainly butyric acid, followed by caproic acid. Caprylic acid has a rancid soap-like flavour, capric and lauric acids only have soapy flavours. Odour (and taste) threshold concentrations in butter made from sweet cream are 50 (60) mg/kg for butyric acid, 85 (105) mg/kg for caproic acid, 200 (120) mg/kg for caprylic acid, >400 (90) mg/kgfor caprinic (capric) acid and >400 (130) mg/kg for lauric acid, respectively. In long term stored butter, active oxidative rancidity products are (E)-non-2-enal, (Z)-non-2-enal in particular, while less active products are (Z)-hept-4-enal, oct-l-en-3-one and others. The rancid and soapy odour in butter can also be caused by contamination with anion active detergents, such as natriumdodecyl sulfate. 

The kernel oil is obtained by expelling, usually followed by solvent extraction. The oil superficially resembles coconut oil in chemical and physical properties. The free fatty acid of the crude oil varies from 0.5 to 10%, plantation oils normally having the lowest values. The refined oil keeps well but has a tendency to form soapy rancid off-flavours under conditions in which microbial or lipolytic activity has not been controlled. 

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