Optimization of equilibrium headspace analysis of volatile flavor compounds of malaysian soursop (Annona muricata): Comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC-TOFMS)

Headspace solid-phase microextraction (HS-SPME) coupled to comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC-TOFMS) was applied for equilibrium headspace analysis of Malaysian soursop (Annona muricata) volatile flavor compounds. A two-level fractional factorial design (25-1) was used to determine the effect of SPME variables, namely, SPME fibers, adsorption temperature, extraction time, amount of salt, sample amount and sample concentration on the extraction efficiency of volatile flavor compounds. A total of 37 volatile compounds were identified, comprising 21 esters, 6 alcohols, 3 terpenes, 2 acids, 2 ketones, 2 aldehydes and an aromatic with different hydrophobicities (log P) ranging between −0.14 and 4.83. Extraction using 10 g of diluted (5% w/w) blended soursop pulp with CAR/PDMS fiber at 25 °C for 30 min and 30% (w/w) of NaCl under stirring mode resulted in the highest extraction efficiency of volatile flavor compounds. The principal component analysis score discriminated the influence of SPME variables on the equilibrium headspace concentration of target volatile compounds.

Research highlights
► Soursop (Annona muricata) is among the important tropical fruits that contribute to the economic growth of some tropical countries, namely, tropical America, Australia, Africa and Malaysia.
► Soursop has a pleasant, distinctive aroma that is described as a custard-like flavor when it is ripe.
► The present study demonstrated that the rapid and simple HS-SPME technique coupled to GC×GC-TOFMS is a powerful technique for the qualitative characterization of soursop volatile flavor compounds.
► A total of 135 compounds extracted using the HS-SPME method were resolved and identified by GC×GC-TOFMS, of which 37 compounds were identified as the key volatile compounds of soursop flavor. In addition, the ordered structures of different homologous series were also observed, comprising ethyl esters, methyl esters, unsaturated esters, alcohols, hydroxylated esters and acids.