Development and testing of instruments and a process for color measurement as methods to determine cocoa bean quality
1990
Wahyudi, Teguh
Study to assess the change in cocoa bean quality parameters was made. The study included the testing of existing quality assessment methods, the testing of appropriateness in the use of fermentation index and color measurement as an indirect quality assessment. The possibility of using a simple photodiode sensing instrument as a cocoa color difference meter was also studied. The fermentation index value increased from 0.47 to 1.30 for different fermentation durations. Cocoa bean acidity (pH) decreased from 6.46 to 4.82. Reducing sugars increased from 0.27 to 1.01 %, while free amino acids increased from 0.27 to 0.67 % for the same fermentation durations. Anthocyanin content decreased from about 50.6 to 15.3 %, yellow/brown pigment polymers increased from about 23.2 to 53.8 %, and no significant changes for red pigment polymer, within the changes of cocoa color categories 1 to 5. The test of quality assessment methods showed that the cut-test score and taste-test methods were not adequate to assess bean quality objectively. The fermentation index method was useful to distinguish different bean samples from 5 color categories. The fermentation index related well with other quality parameters, such as pH, reducing sugars, free amino acids, and cocoa color pigments. Direct color measurement method (in terms of L, a, and b color indicator values) had a good relationship with fermentation index, pH, reducing sugars, and free amino acids. Color measurement was appropriate to estimate cocoa bean quality. Cocoa color measurements using the developed color measuring instrument were found to be acceptable since the results had a good relationship with fermentation index.
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