To characterize the key odorants and elucidate the flavor profiles of compound fermented beverages after fermentation, single-compound fermented beverages (GW, AW) and a compound fermented beverage (CW) were prepared using Italian Riesling grapes and SirPrize apples as raw materials. The flavor and metabolite profiles were systematically analyzed by integrating flavoromics (comprehensive two-dimensional gas chromatography–time-of-flight mass spectrometry, GC × GC–TOF MS) and metabolomics (LC–MS/MS). The results demonstrated that CW exhibited the most favorable acid/reducing sugars (2.18), imparting a drier taste and superior stability. Compounds with relative odor activity values (rOAV) greater than 1—including 3-methyl-1-butyl acetate, ethyl hexanoate, ethyl butanoate, and ethyl octanoate—collectively contributed prominent fruity, floral, and sweet aromas to all three wine types. Ethyl decanoate provided an additional distinctive traditional fruity note specifically to AW, while 1-octen-3-ol contributed a mushroom-like aroma to both GW and CW. Moreover, 3-methylbutanal, 4-ethyl-2-methoxyphenol, and ethyl 3-methylbutanoate added additional significant aroma contributions to CW, imparting floral, clove-like, and fruity notes, respectively. Notably, ethyl hexanoate (fruity aroma) exhibited a remarkably high rOAV of 27.43 in CW, significantly surpassing its levels in the single-substrate fermentations. Lipid metabolism and the phenylpropanoid pathway were significantly activated in CW, facilitating the coordinated synthesis of esters and phenolic compounds. Sensory attribute network analysis further confirmed that CW possessed more pronounced “sweet”, “fruity”, and “floral” characteristics. Correlation analysis revealed significant relationships between volatile organic compounds (VOCs) and total soluble solids (TS), titratable acidity (TA), the TA/TS ratio, and metabolite levels, underscoring the close connections among physicochemical properties, precursor/intermediate metabolites, and flavor formation. Comprehensive analysis of non-volatile metabolites and flavor-associated VOCs revealed variety-specific characteristics and compounding effects, providing valuable insights for enhancing the quality of compound fermented beverages.

We investigated the dynamic changes in volatile aroma compound profiles (types and concentrations) and associated gene expression patterns in both the peel and pulp tissues of apples during fruit maturation. This study aimed to elucidate the metabolic regulatory mechanisms underlying volatile aroma biosynthesis in Malus domestica “Ningqiu” apples, thereby providing theoretical support for the comprehensive utilization of aroma resources. Our methodological framework integrated headspace solid-phase microextraction gas chromatography–mass spectrometry (HS-SPME-GC-MS), ultra-high-performance liquid chromatography–orbitrap mass spectrometry (UHPLC-OE-MS), and Illumina high-throughput sequencing to generate comprehensive metabolomic and transcriptomic profiles of peel and pulp tissues. Critical differential aroma compound classes were identified, including esters, aldehydes, alcohols, terpenoids, and ketones, with their metabolic pathways systematically mapped through KEGG functional annotation. Our findings revealed substantial transcriptomic and metabolomic divergence across carotenoid, terpenoid, and fatty acid metabolic pathways. Integrative analysis of multi-omics data revealed 26 and 31 putative biologically significant hub genes in peel and pulp tissues, respectively, putatively associated with the observed metabolic signatures. Among these, five core genes—farnesyl diphosphate synthase (FDPS1.X1), alcohol acyltransferases (AAT1 and AAT3), alcohol dehydrogenase (ADH3), and carotenoid cleavage dioxygenase (CCD3)—were recognized as shared regulatory determinants between both tissue types. Furthermore, terpene synthase (TPS7) emerged as a peel-specific regulatory factor, while hydroperoxide lyase (HPL2), alcohol dehydrogenases (ADH2 and ADH4), and alcohol acyltransferase (AAT2) were identified as pulp-exclusive modulators of metabolic differentiation. The experimental findings provide foundational insights into the molecular basis of aroma profile variation in Malus domestica “Ningqiu” and establish a functional genomics framework for precision breeding initiatives targeting fruit quality optimization through transcriptional regulatory network manipulation.

The aim of this study was to identify the aromatic compounds present in different apple varieties and to gain insights into the changes in the aromatic compounds during ripening. Three apple varieties (“Red Astrachan”, “Ning Qiu”, and “Golden Delicious”) at different stages of ripening were selected for this study; their peel and pulp were analyzed via headspace solid-phase microextraction (HS-SPME)–gas chromatography–mass spectrometry (HS-SPME-GC-MS), and 30 volatile compounds were identified. The samples’ differences were analyzed using heat map cluster analysis, principal component analysis (PCA), and an independent samples t-test. The results showed that the content of aromatic compounds in the peel was higher than that in the pulp. The relative content of esters in the aromatic compounds of the three apple varieties followed the order of pulp > peel and “Ning Qiu” > “Golden Delicious” > “Red Astrachan”. This suggests that “Ning Qiu” combines the advantages of its parents in terms of its aroma content. The highest concentrations of aroma compounds in “Red Astrachan” and “Ning Qiu” accumulate before the ripening stage, and care should be taken to choose an appropriate harvesting time according to the different needs during production. The main compounds of “Red Astrachan” are aldehydes and C8 esters, while those of “Ning Qiu” and “Golden Delicious” are alkenes and esters. After analyzing the relative odor activity values (rOAVs) of key volatile compounds and their aroma descriptors during the harvest period, acetic acid pentyl ester, butanoic acid hexyl ester, hexanoic acid hexyl ester, and 2-ethyl-1-Hexanol were found to contribute the most to the overall flavor of the peel and pulp. “Ning Qiu” combines the parental advantages of the concentrated peel of “Red Astrachan” and the astringent pulp of “Golden Delicious”, with compounds in its composition that give a pleasing aroma. Mature “Ning Qiu” fruits have a more intense aroma and fruity flavor. The development of flavor-specific varieties has provided the theoretical basis for future research in molecular hybridization, molecular-assisted breeding, and the molecular biology of apple flavor synthesis and metabolism.

Flower bud formation in the apple tree life cycle is associated with multiple biological processes. To explore the physiological and molecular mechanisms underlying the protein and metabolite changes in buds with different flowering capabilities, axillary buds with no flowering (Ab), long-shoot buds with a low flowering rate (Lb), and spur buds with a higher flowering rate than the Lb (Sb) were analyzed using a Tandem Mass Tag™ proteomic technique in combination with nLC–MS/MS analyses. We identified 471 (88 up- and 383 down-regulated), 459 (176 up- and 283 down-regulated), and 548 (387 up- and 161 down-regulated) differentially expressed proteins in Sb vs. Lb, Sb vs. Ab, and Lb vs. Ab, respectively, that were involved in carbohydrate, amino acid and lipid transport, and metabolism. Additionally, 110 (91 increased and 19 decreased), 89 (71 increased and 18 decreased), and 99 (37 increased and 62 decreased) metabolites having significantly different levels were identified in Sb vs. Lb, Sb vs. Ab, and Lb vs. Ab, respectively. The identified metabolites were related to amino acids and their isoforms, sugars and polyols, and organic acids, and occurred at significantly greater levels in the Sbs than the other buds. Thus, flower bud formation is a complex process that involves various biochemical materials and signals, such as carbohydrates, amino acids and their isoforms, and organic acids.

There has been growing interest in examining the potential of non-bagging patterns due to the decline of fruit inner quality and the increase in labor force cost and ecological pollution. Spraying a non-bagging film agent is an important method for non-bagging cultivation. This paper aims to study the effects of non-bagging film agents on the contents of mineral elements and flavonoid metabolites in apple fruits and determine the feasibility of this method. Fuji apples were used as the sample material and treated individually with two non-bagging film agents, namely, humic acid film (ABM) and Pirrio calcium film (CAM). Also, two control groups, namely, the clear water spraying without bagging group (CK) and the bagging group (TCK), were set in this study to measure the contents of mineral elements and flavonoid metabolites in these apples. Compared with those two control groups, the spraying treatment groups with two kinds of non-bagging film agents present a significant difference between their total contents of mineral elements, with the total content of mineral elements of apples in the ABM treatment group being 1.36 times the content of apples in the CK group. In terms of the flavonoid metabolites, only Astragalin, Tiliroside, Homoplantaginin, Phlorizin, Apigenin, Hesperidin, Oroxin A, and Kaempferol present significant differences in their proportions in apples, and there are no significant differences among the proportions of other compounds. Individual spraying of two kinds of non-bagging film agents can significantly increase the total contents of mineral elements in apples, with slight effects on the contents of flavonoid metabolites in these fruits. Therefore, both film agents can be used for cultivating Fuji apples.

The ‘Opal’ apple, a crossbreed between the ‘Topaz’ and ‘Golden Delicious’ varieties, has a unique crunchy, a tangy flavor, slow browning rate that can keep long-lasting freshness after being sliced up. With ‘Fuji’ apples as reference controls, the content of mineral elements, and their key metabolites in the pulps of two kinds of apples were analyzed to clarify nutritional properties and slow browning features in ‘Opal’ apples. In this study, the differential metabolites of the two cultivars of apple were statistically analyzed with the differential principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) using UHPLC-LTQ-Orbitrap MS, combined with non-targeted metabolomics technology, to identify the key differential metabolites in the two varieties of apple. The results showed that there was a total of 147 significantly differential metabolites in 10 categories, of which phenylpropanoids and polyketides account for the highest proportion, Through KEGG pathway analysis, the differential compounds in the two apple cultivars were annotated into 52 pathways, and they were significantly enriched in the two pathways ABC transporters and Flavonoid biosynthesis. The results can lay a theoretical basis for researches on apple quality and provide data support for the indepth development of different apple products.