Polyphenol oxidase (PPO) is one of the most important factors affecting the browning of fresh-cut fruit and vegetable products. In this research, the effect of aromatic hydrosol on the activity of PPO and its biological antioxidant effect were studied. Aromatic hydrosol extracted from 12 kinds of aromatic plants by steam distillation all inhibited the activity of PPO. Eight of the 12 aromatic hydrosols had a significant scavenging effect on 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2’-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cation, and 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxide-1-oxyl (PTIO) radicals. Total antioxidant capacity assay showed that they had strong antioxidant activity. Analysis by electronic nose and gas chromatography-mass spectrometry (GC-MS) showed that terpenoids and aromatic compounds were the major volatile components of aromatic hydrosol. The efficacy of aromatic hydrosol was evaluated in preserving the quality of fresh-cut mushrooms (Agaricus bisporus). The results showed that compared with the control group, the PPO activity in mushrooms treated with aromatic hydrosol was inhibited, and the increase in browning index (BI) was delayed. In addition, total phenol content, hardness, mass loss and total microbial load were effectively controlled. These results indicate that aromatic hydrosol treatment has a positive effect on maintaining the quality of fresh-cut mushrooms.

The contents of taste and flavor compounds of Xingning Dancong tea at different processing stages were determined by headspace solid-phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS), high performance liquid chromatography (HPLC), and spectrophotometry to explore the effect of each processing stage on tea quality. The results showed that during the production process of Xingning Dancong tea, the contents of taste substances such as water extracts, tea polyphenols, catechin compounds, proteins, free amino acids, theanine, caffeine, and soluble sugars showed a decreasing trend. The astringency and bitterness of tea were reduced, while the fresh and brisk taste was enhanced. In terms of volatile components, the relative contents of alcohols, alkenes, and esters decreased, while the relative contents of alkanes, ketones, aldehydes, and heterocyclic substances increased. Terpene and β-pinene, contributing to a grassy flavor, gradually dissipated, while the relative contents of compounds contributing to floral and fruity aromas such as dihydroactinidiolide, linalool oxide Ⅱ, linalool oxide Ⅳ, benzaldehyde, and phytone increased significantly. The changes in tea flavor substances occurred mainly during the shaking, fermentation, high-temperature fixation and baking stages, ultimately forming Xingning Dancong tea with a rich floral and fruity flavor and a strong and mellow taste.