CHARACTERISATION OF VOLATILE COMPOUNDS OF COCOA HUSK USING HEADSPACE SOLID-PHASE MICROEXTRACTION AND GAS CHROMATOGRAPHY-OLFACTOMETRY ANALYSIS

Abstract

Cocoa seeds (Theobroma cacao L.) are known for their variety of products exhibiting pleasant sensory properties. Cocoa husk is a residue from the cocoa industry which can be used as flavoring material. A headspace solid-phase microextraction (HS-SPME) procedure followed by gas chromatography-olfactometry (GC-O) analysis is proposed to determine aroma-active compounds in cocoa husk. To determine optimal extraction conditions of the HS-SPME technique: fiber type (100 µm polydimethylsiloxane, 85 μm Carboxen/polydimethylsiloxane, 65 μm polydimethylsiloxane/divinylbenzene and 50/30 µm divinylbenzene/Carboxen/polydimethylsiloxane), extraction time (15, 20 and 25 min) and temperature (40, 50 and 60 ^oC) were evaluated using surface response design. Response variables were global odor from the fibers and total chromatographic areas. GC-O in combination with HS-SPME using divinylbenzene/Carboxen/polydimethylsiloxane fiber operated at 60 ^oC for 22 min could isolate most of the volatile compounds from cocoa husk. A total of 169 of them were identified, including 28 acids, 23 esters, 22 pyrazines, 16 terpenes, 12 ketones, 8 alcohols, 3 aldehydes, among others. Among them, the most odor-active compounds were acetic acid, 2,3-diethyl-5-methylpyrazine, 2-ethyl-3,5-dimethylpyrazine, 3-methylbutanal, phenylacetaldehyde, 3,5-diethyl-2-methylpyrazine, 4-hidroxy-2,5-dimethyl-3(2H)-furanone, 3-methylbutanoic acid, 2-ethyl-5-methylpyrazine, 2,6-dimethylpyrazine, dimethyl trisulfide, 2,3,5,6-tetramethylpyrazine, 2,3,5-trimethylpyrazine, 2-methylbutanal, 2-methylpyrazine, 2-phenylacetic acid, linalool, butanoic acid, 2-methylbutanoic acid, 2,5-dimethylpyrazine and 2-phenylethyl acetate. The present method may be applied as a quality control tool for industrial laboratories.