Effect of autoclaving cocoa nibs before roasting on the precursors of the Maillard reaction and pyrazines

Nibs of raw cocoa (N) were roasted (R) at 150 degreesC for 38 min. Some samples were autoclaved at 121 degreesC for 15 min (A) and roasted (AR) at 150 degreesC for 38 min. The samples were then analysed for moisture content, water activity (a(w)), reducing sugar and amino group (alpha -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 quantified by solid phase micro extraction-gas chromatography (SPME-GC). There was a reduction in the levels of alpha -N, 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 significantly influenced the levels of compounds which contribute to cocoa flavour formation and increased the concentration of tri- and tetramethylpyrazines in the headspace of cocoa samples. Autoclaving prior to roasting also affected the sensory properties of the samples.