Nibs of raw cocoa (N) were roasted (R) at 150 °C for 38 min. Some samples were autoclaved at 121 °C for 15 min (A) and roasted (AR) at 150 °C for 38 min. The samples were then analysed for moisture content, water activity (a w), reducing sugar and amino group (a-N) levels and, absorption at 275 nm (A 275) for a trichloro acetic acid (TCA) extract and at 280 nm (A 280) for the distillate. Tri-and tetramethylpyrazines were quanti®ed by solid phase micro extraction-gas chromatography (SPME-GC).

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... re was a reduction in the levels of aN , in the order N > A > R > AR. The same sequence was observed for reducing sugars. The tetramethylpyrazine had an Area pyrazine / Area internal standard of N < R < A < AR and for trimethylpyrazine the order was N < A < R < AR. After autoclaving, the A tetra /A tri decreased from 31.30 (N) to 11.06 (A). With roasting, this ratio was 2.18 (R) and 2.58 (AR). Autoclaving nibs before roasting signi®cantly in¯uenced the levels of compounds which contribute to cocoa ¯avour formation and increased the concentration of tri-and tetramethylpyrazines in the headspace of cocoa samples. Autoclaving prior to roasting also a€ected the sensory properties of the samples.