Enhance rice-like aroma of on <i>Strobilanthes tonkinensis</i> var. <i>tonkinensis</i> extract using hydroxypropyl- <i>β</i> -cyclodextrin

Valued for its distinctive and intense rice-like aroma, Strobilanthes tonkinensis var. tonkinensis (S. tonkinensis) is an edible plant widely used as a flavoring agent. However, its commercial development is severely hampered by the intrinsic instability of its key odorant, 2-propionyl-3,4,5,6-tetrahydropyridine (2-PTHP). This compound undergoes progressive degradation during storage, resulting in a marked attenuation of the characteristic rice-like aroma. To minimize flavor loss during processing, ultrasonic-assisted extraction (600 W for 15 min for 50°C) was utilized to obtain S. tonkinensis extracts. The volatile profile of the extract was characterized by gas chromatography-mass spectrometry (GC-MS) and odor activity value (OAV) analysis, leading to the identification of 28 key aroma compounds, among which five pyridine derivatives showed exceptionally high OAVs ( >400), confirming their dominant role. Furthermore, nontargeted liquid chromatography-mass spectrometry (LC-MS) analysis demonstrated that 2-PTHP primarily exists in solution as stable dimeric adducts. The efficacy of hydroxypropyl-β-cyclodextrin (HP-β-CD) in preserving the rice-like aroma was then systematically evaluated, and the results demonstrated that the addition of 1% HP-β-CD could enhance the concentration of the key odorant 2-PTHP by up to 20%. This study proposes a novel strategy for stabilizing volatile imine aromas in food systems, underscoring the potential of cyclodextrins as versatile tools for aroma preservation and restoration.