The synthesis of papaya fruit flavor-related linalool was regulated by CpTPS18 and CpNAC56.

Papaya is a tropical fruit crop renowned for its rich nutrition, particularly pro-vitamin A. Aroma substances are a major component of fruit quality. While extensive research has been conducted on papaya aroma, there has been a notable lack of in-depth research into a specific class of substances. To bridge this gap, our study focused on analyzing the aroma components of various papaya varieties and their biosynthesis pathways. We compared the volatile components of three papaya varieties with distinct flavors at various ripeness stages. A continuous accumulation of linalool, a volatile compound, in the 'AU9' fruit was detected as it matured. The linalool content reached 56% of the total volatile components upon full ripening. Notably, this percentage was significantly higher than that observed in the other two varieties, 'ZhongBai' and 'Malaysian 7', indicating that linalool serves as the primary component influencing the papaya's odor. Subsequently, we identified CpTPS18, a gene associated with linalool biosynthesis, and demonstrated its ability to catalyze linalool production from GPP and enhance its accumulation through overexpression in papaya fruits, both in vivo and in vitro. Based on transcriptomic analysis, it was predicted that CpMYB56 and CpNAC56 may transcriptionally activate the expression of CpTPS18. Subsequent yeast one-hybrid assay and dual luciferase analysis revealed that CpNAC56 activates the transcription of CpTPS18. Transient overexpression in vivo demonstrated that this gene could upregulate the expression of CpTPS18 and promote linalool accumulation. These results uncovered the primary volatile molecule responsible for papaya fruit odor and identified two major genes influencing its biosynthesis. The genomic resources and information obtained from this study will expedite papaya improvement for fruit quality.

Characterization of odor-active compounds in moso bamboo (Phyllostachys pubescens Mazel) leaf via gas chromatography-ion mobility spectrometry, one- and two-dimensional gas chromatography-olfactory-mass spectrometry, and electronic nose.

The leaf of moso bamboo (Phyllostachys pubescens Mazel) is rich in odorant compounds, which is important natural materials for the production of flavor. It also contains phenolic acids, amino acids and peptides, which is a potential source of natural bioactive compounds. The study of odor-active compounds in bamboo leaves can provide a basis for the discovery of natural flavor. The leaf, stem, and powder of moso bamboo were analyzed by gas chromatography-ion mobility spectrometry (GC-IMS). Main odor-active compounds in moso bamboo leaf were analyzed and characterized by (1) a gas chromatography olfactory mass spectrometry (GC-O-MS), (2) two-dimensional gas chromatography olfactory mass spectrometry (GC × GC-O-MS) and (3) electronic nose (E-nose). Based on aroma extract dilution analysis (AEDA), 13 key odor-active compounds with high flavor dilution (FD) factor (≥27), including 3-methyl-1-butanol, (E)-2-hexenal, ethyl hexanoate, (Z)-4-heptenenal, 6-methyl-5-hepten-2-one, octanal, ethyl (Z)-3-hexenoate, 1-hexanol, (Z)-3-hexen-1-ol, (E, E)-2,4-heptadienal, (Z)-2-hexen-1-ol, 1-octen-3-ol and benzaldehyde, were further analyzed. The compounds detected by the above four methods were (E)-2-hexenal, 6-methyl-5-hepten-2-one, octanal, (E, E)-2,4-heptadienal, 1-octen-3-ol and benzaldehyde, and all of which were the main and potential odorants of moso bamboo leaf.

Sensory-Based Identification of Aroma-Active Compounds in Hotpot Seasoning before and after Boiling.

Boiling, the most frequent edible way to hotpot seasoning (HS), exerts a significant impact on the aroma of HS. The present study employed, for the first time, a novel switchable system between GC-O-MS and GC×GC-O-MS (SGC/GC×GC-O-MS) to study the aroma compounds of HS and hotpot seasoning boiling liquid (HSBL). A total of 79 aroma compounds and 56 aroma-active compounds were identified. The aroma extract dilution analysis (AEDA) was used to analyze the differences between the key aroma-active components in the HS and HSBL. The results showed that 13 aroma-active components were significantly affected by boiling, such as D-limonene, methional, and linalool. Moreover, a total of 22 key aroma-active components were identified through the odor activity values (OAVs) calculation. Of them, (E)-2-octenal (fatty) and linalool showed a significant difference, suggesting them to be the most critical aroma-active compounds in the HSBL, and HS, respectively. Finally, the correlation between key aroma-active compounds and the sensory properties of HS and HSBL was studied. These results demonstrated that the OAVs of key aroma-active compounds could characterize the real information of samples through bidirectional orthogonal partial least squares (O2PLS). The analysis results were consistent with the sensory evaluation results.