The unpleasant stale note is a negative factor hindering the consumption of instant ripened Pu-erh tea products. This study focused on investigating volatile chemicals in instant ripened Pu-erh tea that could mask the stale note via sensory evaluation, gas chromatography-mass spectrometry (GC-MS), and gas chromatography-olfactometry (GC-O) analyses. GC-MS and GC-O analyses showed that linalool, linalool oxides, trans-β-ionone, benzeneacetaldehyde, and methoxybenzenes were the major aroma contributors to the simultaneous distillation and extraction (SDE) extract of instant ripened Pu-erh tea. Sensory evaluation showed that the SDE extract had a strong stale note, which was due to methoxybenzenes. By investigating suppressive interaction among flavour components, the stale note from methoxybenzenes was shown to have reciprocal masking interactions with sweet, floral, and green notes. Moreover, the validation experiment showed that the addition of 40 μg/mL of trans-β-ionone in the instant ripened Pu-erh tea completely masked the stale note and improved the overall aromatic acceptance. These results elucidate the volatile chemicals that could mask the stale note of instant ripened Pu-erh tea products, which might help to develop high quality products made from instant ripened Pu-erh tea.

Sensory evaluation, GC–MS and omission test were used to characterize aromas of noninstant Oolong tea (NIOT), original instant Oolong tea (OIOT) and its counterparts treated by two enzyme extracts from Aspergillus niger. The results showed that OIOT had stronger sweet, fruity, and roasted notes, but weaker grass and floral notes than NIOT. After treated by the crude enzymes extracted from the fermented broth from tea waste (TW) medium, the treated‐OIOT had an improved aroma similar to that of NIOT, due to the increases of 2‐pentyl‐furan and 3‐cis‐hexen‐1‐ol. In comparison, after the treatment of crude enzymes from wheat bran and orange peel (WBOP) medium, the treated‐OIOT showed significantly aroma difference from NIOT and OIOT, which was attributed to the increases of 3‐cis‐hexen‐1‐ol, γ‐terpinene, and β‐trans‐farnesene. These results revealed that the original aroma of OIOT could be effectively modified and improved by the enzyme extracts, particularly by that from the TW medium. Practical applications Tea is one of the most popular beverages all over the world. Instant tea is an important tea product that is processed from teas by extraction, concentration and drying. Instant tea is more convenient than teas for industrially producing tea foods such as tea beverage, tea break, and tea ice cream. However, the aroma profile of instant tea is always inferior to those of the original unprocessed noninstant teas, because the characteristic aroma of the original unprocessed tea could undergo significant changes during the preparation of instant tea. The present manuscript shows two enzyme extracts from Aspergillus niger could improve the aroma of instant Oolong tea, providing interesting information to promote the aroma of instant tea via enzymatic treatments, which may help to develop effective approaches to enhancing the quality of instant teas.

De novo transcriptome assembly for the five major organs of Zanthoxylum armatum and the identification of genes involved in terpenoid compound and fatty acid metabolism Abstract Background: Zanthoxylum armatum (Z. armatum) is a highly economically important tree that presents a special numbing taste. However, the underlying regulatory mechanism of the numbing taste remains poorly understood. Thus, the elucidation of the key genes associated with numbing taste biosynthesis pathways is critical for providing genetic information on Z. armatumand the breeding of high-quality germplasms of this species.Results: Here, de novo transcriptome assembly was performed for the five major organs of Z. armatum, including the roots, stems, leaf buds, mature leaves and fruits. A total of 111,318 unigenes were generated with an average length of 1014 bp. Additionally, a large number of SSRs were obtained to improve our understanding of the phylogeny and genetics of Z. armatum. The organ-specific unigenes of the five major samples were screened and annotated via GO and KEGG enrichment analysis. A total of 53 and 34 unigenes that were exclusively upregulated in fruit samples were identified as candidate unigenes for terpenoid biosynthesis or fatty acid biosynthesis, elongation and degradation pathways, respectively. Moreover, 40 days after fertilization (Fr4 stage) could be an important period for the accumulation of terpenoid compounds during the fruit development and maturation of Z. armatum. The Fr4 stage could be a key point at which the first few steps of the fatty acid biosynthesis process are promoted, and the catalysis of subsequent reactions could be significantly induced at 62 days after fertilization (Fr6 stage). Conclusions: The present study realized de novo transcriptome assembly for the five major organs of Z. armatum. To the best of our knowledge, this study provides the first comprehensive analysis revealing the genes underlying the special numbing taste of Z. armatum. The assembled transcriptome profiles expand the available genetic information on this species and will contribute to gene functional studies, which will aid in the engineering of high-quality cultivars of Z. armatum.