Ghanaian cocoa bean fermentation characterized by spectroscopic and chromatographic methods and chemometrics.
Export of cocoa beans is of great economic importance in Ghana and several other tropical countries. Raw cocoa has an astringent, unpleasant taste, and flavor, and has to be fermented, dried, and roasted to obtain the characteristic cocoa flavor and taste. In an attempt to obtain a deeper understanding of the changes in the cocoa beans during fermentation and investigate the possibility of future development of objective methods for assessing the degree of fermentation, a novel combination of methods including cut test, colorimetry, fluorescence spectroscopy, NIR spectroscopy, and GC-MS evaluated by chemometric methods was used to examine cocoa beans sampled at different durations of fermentation and samples representing fully fermented and dried beans from all cocoa growing regions of Ghana. Using colorimetry it was found that samples moved towards higher a* and b* values as fermentation progressed. Furthermore, the degree of fermentation could, in general, be well described by the spectroscopic methods used. In addition, it was possible to link analysis of volatile compounds with predictions of fermentation time. Fermented and dried cocoa beans from the Volta and the Western regions clustered separately in the score plots based on colorimetric, fluorescence, NIR, and GC-MS indicating regional differences in the composition of Ghanaian cocoa beans. The study demonstrates the potential of colorimetry and spectroscopic methods as valuable tools for determining the fermentation degree of cocoa beans. Using GC-MS it was possible to demonstrate the formation of several important aroma compounds such 2-phenylethyl acetate, propionic acid, and acetoin and the breakdown of others like diacetyl during fermentation. Practical Application: The present study demonstrates the potential of using colorimetry and spectroscopic methods as objective methods for determining cocoa bean quality along the processing chain. Development of objective methods for determining cocoa bean quality will be of great importance for quality insurance within the fields of cocoa processing and raw material control in chocolate producing companies.
Aculey
Patrick C
PC
Cocoa Research Inst. of Ghana, Tafo-Akim, Ghana.
Snitkjaer
Pia
P
Owusu
Margaret
M
Bassompiere
Marc
M
Takrama
Jemmy
J
Nørgaard
Lars
L
Petersen
Mikael A
MA
Nielsen
Dennis S
DS
D000085:Acetates / Q000032:analysis / Q000737:chemistry; D000093:Acetoin / Q000032:analysis / Q000737:chemistry; D002099:Cacao / Q000737:chemistry*; D003116:Color; D003124:Colorimetry; D003931:Diacetyl / Q000032:analysis / Q000737:chemistry; D005285:Fermentation; D005504:Food Analysis / Q000379:methods*; D005511:Food Handling / Q000379:methods*; D008401:Gas Chromatography-Mass Spectrometry; D005869:Ghana; D015233:Models, Statistical; D010626:Phenylethyl Alcohol / Q000031:analogs & derivatives / Q000032:analysis / Q000737:chemistry; D025341:Principal Component Analysis; D011422:Propionates / Q000032:analysis / Q000737:chemistry; D011786:Quality Control; D012639:Seeds / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D019265:Spectroscopy, Near-Infrared; D055549:Volatile Organic Compounds / Q000032:analysis / Q000737:chemistry
D000085:Acetates; D011422:Propionates; D055549:Volatile Organic Compounds; C054590:2-phenylethyl acetate; D000093:Acetoin; C029658:propionic acid; D003931:Diacetyl; D010626:Phenylethyl Alcohol