Gas-liquid partitioning and olfactory interplay between isoamyl alcohol and typical odorants in binary hydroalcoholic...

Intermolecular interactions among volatile typical odorants define the characteristic sensory profile of navel orange brandy, with isoamyl alcohol-the dominant fusel higher alcohol-functioning as a pivotal flavor regulator. Excess isoamyl alcohol blunts distinct citrus fruity notes and destroys organoleptic harmony; nevertheless, systematic mechanistic explorations targeting citrus brandy remain insufficient. Herein, simplified 54% (v/v) binary hydroalcoholic models were established to exclude complicated coexisting matrix interference, allowing exclusive dissection of pairwise odorant interactions. A dual analytical workflow combining HS-SPME-GC-MS quantification and sigmoidal olfactory threshold fitting was constructed to elucidate concentration-dependent (0-800 mg/L isoamyl alcohol) variations in gas-liquid partitioning and olfactory interplay across 18 citrus typical odorants. In binary hydroalcoholic systems, isoamyl alcohol continuously hampered the volatilization of fatty acid ethyl esters, and inhibitory potency declined progressively as carbon chains elongated. This fusel alcohol imposed dual concentration-mediated effects on linear aliphatic alcohols: concentrations ≤ 400 mg/L boosted odorant release into the headspace, while higher dosages suppressed partitioning, and such bidirectional shifts were more prominent for short-chain analogs. Acyclic terpenols suffered steady volatility attenuation with elevated isoamyl alcohol, whereas monocyclic D-limonene and α-terpineol underwent initial promotion followed by inhibition, with respective turning points at 400 mg/L and 600 mg/L. Polar minor volatiles (furfural, 4-ethylphenol, 3-hydroxy-2-butanone) exhibited gradual depletion in headspace concentration, while weakly polar styrene displayed consistent partitioning elevation. Olfactory evaluation of all 18 binary blends identified seven masking, seven additive and four synergistic binary pairs. Overall, isoamyl alcohol concealed ester-originated fruity aromas yet intensified the sensory perception of alcoholic and cyclic terpene notes. The quantitative datasets acquired in this research deliver reliable theoretical basis and technical guidance for precise isoamyl alcohol modulation in citrus brandy manufacturing. Notably, the present work only addresses pairwise interactions within simplified binary hydroalcoholic models; multi-component flavor coupling effects and verification on naturally aged authentic brandy will be explored in subsequent research.