Identification of aroma-active compounds in 'wonderful' pomegranate fruit using solvent-assisted flavour evaporation and headspace solid-phase micro-extraction methods

During the last few years, there has been a tremendous increase in consumption of pomegranate fruit and juice. Nevertheless, very little is yet known regarding the volatile constituents that determine the unique aroma of pomegranate fruit. We extracted aroma volatiles from fresh 'Wonderful' pomegranate juice using solvent-assisted flavour evaporation (SAFE) and headspace solid-phase micro-extraction (HS-SPME) methods, and applied gas chromatography-olfactometry (GC-O) ('sniffing') combined with gas chromatography-mass spectrometry (GC-MS) analysis, in order to identify volatile aroma-active compounds. In addition, we performed stir bar sorptive extraction (SBSE) of pomegranate aroma volatiles, coupled with GC-MS analysis, in order to assist in identifying aroma-active compounds. Overall, we tentatively identified 23 volatiles in the SAFE and HS-SPME extracts; they belonged to various chemical classes, including aldehydes, terpenes, alcohols, esters, furans and acids. Using the GC-O nasal impact frequency method, we tentatively detected 12 aroma-active peaks and identified the corresponding odourants by GC-MS. The aroma-active compounds of 'Wonderful' pomegranates were ethyl-2-methylbutanoate (fruity, apple), hexanal (green), beta-pinene (pine, herbal), beta-myrecene (woody, musty), cis-3-hexenal (green), limonene (fruity, musty), cis-2-heptenal (soapy, mushroom), cis-3-hexenol (earthy, grassy), 2-ethylhexanol (floral), beta-caryophyllene (fruity, musty), 2(5H)-furanone (sweet, fruity) and beta-sesquiphellandrene (terpene, almond). Overall, the flavour of 'Wonderful' pomegranate fruit derives from a mixture of various 'green', 'woody', 'earthy', 'fruity', 'floral', 'sweet' and 'musty' notes.