Dynamic characterization of volatile and non-volatile profiles during Toona sinensis microgreens growth in...

Toona sinensis microgreens (TSM) are popular for their aroma similar to Toona sinensis buds (TSB). This study characterized TSM across four developmental stages: sprout-appearing (M1), apical hook opening (M2), cotyledon unfolding and expansion (M3), and fully opened cotyledons (M4). Eighty-two volatile organic compounds (VOCs) were identified, with nineteen VOCs serving as key discriminators. Total VOC content increased during TSM development, with volatile sulfur compounds (VSCs) accounting for 71 %-81 %. Ter-4 (β-Cyclocitral), Ter-23 (α-Selinene) and Sul-13 (3-(Methylthio) propanoic acid ethyl ester) played a crucial role in balancing the overpowering odor-induced VSCs in M4. A total of 888 non-volatile metabolites were identified. Lipids, amino acids, phenolic acids, and flavonoids were the major components and regulated during TSM growth. Twenty-three non-volatile compounds were identified as potential biomarkers in M1, M2, and M4. Copaene, τ-cadinol, 2,3-dihydroxy-3-methylbutanoic acid, 9,10,11-trihydroxy-12-octadecenoic acid and 1-O-caffeoyl-β-d-glucose were screened as hub metabolites, making M1 stage had a woody, herbal aroma and potential bio-activities. Terpenoid (cis- and trans-caryophyllene, ursolaldehyde, sendanolactone, melianone lactone, meliasenin B) accumulation peaked at the M2 stage. Furthermore, cis- and trans-caryophyllene along with the only ester (10-Hydroxydecanoic acid, methyl ester), three dipeptides (L-leucyl-L-phenylalanine, Lysine-phenylalanine and Cyclo (Proline-Valine)) of M2 offered better sensory expectations for consumers. Sulfur metabolism was the most significant biological process in M4 compared to other stages, as all hub metabolites in M4 were VSCs and precursors related to VSC biosynthesis. These results provide insights into metabolic changes across TSM growth, offering valuable information for optimizing its cultivation and utilization.