Preservation of Aroma in Rougui Oolong Tea by Hydroxypropyl-β-cyclodextrin

Oolong tea was highly favored by consumers for its rich aroma. However, there was significant loss of fragrance in Oolong tea products during processing and storage, urgently necessitating the development of corresponding technologies to stabilize aroma molecules. Addressing this, this study investigated the stabilization of aroma compounds in Rougui Oolong tea. Employing spinning cone column distillation, volatile organic compounds (VOCs) were extracted from the tea. The effect of hydroxypropyl-β-cyclodextrin on inhibiting the aromatic loss of these extracted VOCs during storage was assessed using gas chromatography-ion mobility spectrometry. Results showed that after 7, 21, and 42 days of storage at room temperature (25 ℃), the samples treated with hydroxypropyl-β-cyclodextrin (experimental group) consistently contained significantly higher quantities of VOCs compared to the untreated controls (P<0.05), which were 39, 37, and 35 types, respectively. Notably, 21 VOCs, including trans-2-hexenal, 2-heptanone, and 2-hexanone were present at more than double the concentration in the experimental group relative to the control. Furthermore, thermogravimetric analysis indicated that hydroxypropyl-β-cyclodextrin encapsulation slowed the loss of key aroma compounds, specifically 2-methylbutanal and hexyl acetate, and enhanced the thermal stability of α-pinene between 30~100 ℃, suggesting its protective effect on aroma molecules during thermal processing of Oolong tea. In summary, hydroxypropyl -β- cyclodextrin would be an effective fragrance preserving agent for aroma molecules in water-based products of Rougui Oolong tea.