Effects of drying methods on the quality and volatile flavor compounds of oil tea powder

Abstract

Objective: This study aimed to explore suitable drying methods for oil tea powder, making it easier for oil tea consumption and storage. Methods: Spray drying, vacuum freeze drying and vacuum drying were used to dry oil tea soup, and the quality (moisture content, sensory evaluation and color) and volatile substances of dried oil tea powder were evaluated. Results: The sensory score of vacuum freeze-drying oil tea powder was the highest (93), the water content was the lowest (3.78%), and the color was better（ΔE value 49.74). 104 volatile substances were identified from three drying methods of oil tea powder using SPME-GC-MS technology, of which 14 affected the flavor of oil tea powder. The characteristic flavor substances (nonanal, decanal, (Z)-2-decanal, (Z)-2-nonenal, (E) -3,7-dimethyl-2,6-octadienal) of freeze-drying present green fragrance and fat fragrance. The special aromas of spray drying and vacuum drying are (Z)-3,7-dimethyl-2,6-octadienal, (E)-3,7-dimethyl-2,6-octadienal and decanal, presenting green fragrance, fruit fragrance, and wax fragrance. PCA and comprehensive evaluation indicate that vacuum freeze-drying has the best flavor quality, which is consistent with sensory evaluation results. Conclusion: The flavor quality of vacuum freeze-drying was the best.

Keywords

• oil tea power
• spray drying
• vacuum freeze-drying
• vacuum drying
• volatile flavor compounds