2 ethylfuran

The furan standard was procured from Alfa Aesar Co. (Ward hill, MA, USA), while 3-methylfuran was from Acros Co., (Carlsbad, CA, USA), and 2-pentylfuran from Tokyo Chemical Industry Co. (Tokyo, Japan). The other furan derivative standards, including 2-methylfuran, 2,3-dimethylfuran, 2,5-dimethylfuran, 2-ethylfuran, furfural, furfuryl alcohol, 2-butylfuran, and 2-acetylfuran, were from Sigma-Aldrich (St. Louis, MO, USA). The internal standard d4-furan was from Dr. Ehrenstorfer GmbH Co. (Augsburg, Germany). The HPLC-grade methanol was from Merck (Darmstadt, Germany), and the sodium chloride was from Uni Region Bio-Tech (Los Altos, CA, USA). The sodium chloride was purchased from UNI-ONWARD CORP (New Taipei City, Taiwan).

Water used in the experiments was purified by a Milli-Q purification system (Millipore Sigma, Burlington, MA, USA), and solvents used were of HPLC-isocratic grade or higher. The chemicals used as standards in the experiments were purchased from several different vendors. From Acros Organics (Antwerp, Belgium), we purchased 2-hexenal. From Chem Service Inc. (West Chester, PA, USA), we purchased acetophenone, fructose, glucose, and sucrose. From Fluka (Steinheim, Switzerland), we purchased chlorogenic acid and eucalyptol. From Merck (Darmstadt, Germany), we purchased quinic acid. From Polyphenols AS (Sandnes, Norway), we purchased cyanidin-3-O-galactoside. From Sigma-Aldrich (St. Louis, MO, USA), we purchased benzaldehyde, catechin hydrate, citric acid, o-cymene, p-cymene, 2-ethyl furan, ethyl octanoate, (E,E)-2,4-heptadienal, (E,E)-2,4-hexadienal, hexanal, hexanoic acid, 1-hexanol, hexyl acetate, linalool, d-limonene, malic acid, methylbutanal, 3-methyl-1-butanol acetate, 6-methyl-5-hepten-2-one, 4-Methyl-2-pentanol, n-alkane mixture (C7–C30), neryl acetate, 1-octen-3-ol, 1-pentanol, quercetin-3-O-rutinoside, 2-α-pinene, shikimic acid, and γ-terpinene.

Alkane standard solutions from C₈ to C₂₀ (40 mg/L each in hexane) and C₂₁ to C₄₀ (40 mg/L each in toluene) were purchased from Sigma-Aldrich. A standard solution from C₅ to C₁₀ was prepared using pure substances in a ratio resulting in narrow and symmetric peak shapes as described by Weingart, et al.^{35 (link)}.
Pure VOCs were selected according to the SPME/GC-MS results, such as Benzenethanol, β-caryophyllene, trans-2-pentenal, 2-ethylfuran and β-cyclocitral (Sigma-Aldrich); cadinene (a mixture of ɣ-cadinene and δ-cadinene; (BOC Sciences); β-selinene and ledol (Xiamen Freede Industry). Pure VOCs were used in functional assays and for identity confirmation with HS-SPME/GC-MS analysis (Supplementary Fig. S2)