Effect of Roasting on the Development of Flavour in Malaysian Cocoa Beans (Theobroma Cacao L.)

Malaysian cocoa beans have been characterised by chocolate manufacturers as lacking strong Cocoa flavour. To have an insight into the flavour problem, research was carried out to see how roasting would affect the chemical and flavour compliments as well as the acceptability of dark chocolate prepared from the beans. The roasting condition used was 150˚C for 15, 30 and 45 minutes. It was found that a temperature difference existed between the oven temperature and the temperature of the bean during roasting. The difference was 55˚C at the tenth minute and down to 20˚C at the end of the 45 minutes roasting, respectively. The moisture content of the beans decreased with roasting time while the pH remained unchangi2d. Theobromine content decreased by 11.61 per cent after 45 minutes roasting. Total polyphenols decreased 31ightly by 6.21 per cent while total reducing sugar content decreased by 58.54 per cent by the end of 45 minutes roasting, respectively. The total amino acid content also decreased by 61.95 per cent after 45 minutes roasting. No definite pattern of isopentanal development was obtained using the headspace sampling method. A more definite pattern, however, was obtained foe the development of pyrazines. From the four pyrazines detected, tetramethylpyrazine was the major pyrazine that was detected throughout the roasting experiment. Data from the Ranking Preference Test indicated that dark chocolate prepared from the beans roasted at 150˚C for 45 minutes was most preferred. Triangle Test Difference Analysis showed there there was a difference between the dark chocolate prepared from this Malaysian beans and dark chocolate prepared from Ghana beans roasted at 150˚C for 30 minutes. The latter was more preferred over the former. However, Ranking Preference Test for the two samples indicated that the preference was not significant.

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