Bold Roast, Nuts, Praline, Caramel, Cream, Woods, Coffee, Bitters – a broad category in which roasting largely comes into play.
… as Mailliard Reactions help produce furaneol, hyroxymaltol, & cyclotene which contribute caramel tones (particularly 4-hydroxy-2,5- dimethyl-3(2H)-furanone); & pyrazines (nitrogen + carbon compounds) form nut-like flavors (especially 2,3-dimethylpyrazines). More compounds that round-out this category are trimethylpyrazine, tetramethylpyrazine, 3(or 2),5-dimethyl-2(or 3)-ethylpyrazine, 3,5(or 6)-diethyl-2-methylpyrazine, & furfurylpyrrole & the malty 2- + 3-methylbutanal, some the result of Strecker Degradation — an intermediate step that requires compounds created first by Mailliard heat. During Strecker Degradation, amino acids react with a carbonyl group (instead of a reducing sugar as in Maillard Reactions) to generate aldehydes & ketones (the latter often associated with buttery tones & caramel too).
Otherwise, lengthy conching factors for cream notes, & wood used in ferment boxes often impart their own effect.
