Effect of different drying methods on quality of orange dark tea

Orange dark tea (ODT) is widely produced in China, but the quality of traditional sunlight-dried ODT is not satisfactory, thus limiting its industrial production. This study compared the effects of traditional sunlight drying and current hot air drying on ODT quality. Sensory evaluation showed that hot air-dried orange dark tea (HAD) had better peel-tea integration and higher sensory score. Compared with sunlight-dried ODT (SLD), HAD exhibited higher contents of polyphenols, flavonoids, hesperidin and limonin. Gas chromatography-mass spectrometry (GC–MS) analysis of volatile components in the two ODTs identified a total of 102 aroma components, where 22 differential metabolites and 4 key aroma substances (linalool, limonene, β-myrcene and sabinene) were screened. Bioactivity analysis showed that HAD had better inhibitory effect against α-glucosidase and α-amylase activity, indicating superior overall quality. Further analysis of the effect of drying temperatures on ODTs quality exhibited that low temperature drying at 40 to 50 °C endowed ODT with lower bitterness and astringency, richer polyphenols, flavonoids, hesperidin, and free amino acids, also indicating better comprehensive quality. All the results indicate that hot air drying outperforms sunlight drying in improving ODT quality. This study provides a basis for process optimization of ODT.