Effect of the maturation process on fermented cocoa bean I: free amino acids and volatile carbonyls

Abstract

:The prevalence of high acidity in fermented beans, which adversely affects cocoa flavour, is a problem when fermentation (normally up to 2 days in Sri Lanka) extends to 4 days or more. The maturation process, in which beans are held in thin layers at ambient temperatures during which little or no drying occurs and acetic acid is oxidized to CO2, was investigated using a mixture (approximately 4:1) of Forastero and Criollo types. Maturation caused a reduction in free amino acids, except for glutamic and aspartic acids. It also increased the content of volatile carbonyls (principally diacetyl, formaldehyde, acetone, acetaldehyde, butyraldehyde (iso- and n-) and valeraldehyde (iso- and n-)). There appeared to be a relationship between these 2 trends, but the appearance of carbonyls is thought to be due not only to the breakdown of amino acids but to other processes including the oxidative degradation of fatty acids. Roasting caused a further decline in amino acids and rise in carbonyls, presumably due to the Strecker reaction [see Schonberg, A. et al, Chemistry Review (1952) 50, 26].