Elucidating the Formation Pathway of the Off-Flavor Compound 6‑Propylbenzofuran-7-ol

• Published in: Journal of agricultural and food chemistry 2012-10, Vol.60 (40), p.9967-9973
• Main Authors: Sakamaki, Kensuke, Ishizaki, Susumu, Ohkubo, Yasutaka, Tateno, Yoshiyuki, Nakanishi, Akira, Fujita, Akira
• Format: Article
• Language: English
• Subjects: Aldehydes - chemistry; apples; ascorbic acid; Ascorbic Acid - chemistry; Benzofurans - analysis; Benzofurans - chemical synthesis; beverages; Beverages - analysis; Biological and medical sciences; byproducts; citric acid; Food industries; Fruit; Fruit and vegetable industries; Fundamental and applied biological sciences. Psychology; Gas Chromatography-Mass Spectrometry; heat; Hot Temperature; isotope labeling; Malus; mixing; off flavors; Solutions; Taste
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf302762j

In a previous work, we identified 6-propylbenzofuran-7-ol as an off-flavor compound formed from ascorbic acid and (E)-hex-2-enal in a test apple beverage. In this study, we elucidate the pathway by which 6-propylbenzofuran-7-ol formed. Isotope labeling studies revealed that the propyl group of 6-propylbenzofuran-7-ol derives from (E)-hex-2-enal and that 6-propylbenzofuran-7-ol contains carbons 2–6 of ascorbic acid. Two compounds, namely, 2,3-dihydro-6-propylbenzofuran-3,7-diol and 3-(2-furoyl)hexanal, were identified as byproducts of a model reaction of ascorbic acid and (E)-hex-2-enal. Each of these compounds was dissolved in an aqueous solution of citric acid and stored at 60 °C for 1 week. After storage, 6-propylbenzofuran-7-ol was detected from a solution of 2,3-dihydro-6-propylbenzofuran-3,7-diol, but not from 3-(2-furoyl)hexanal. 6-Propylbenzofuran-7-ol was formed by isolating tricyclic hemiacetal lactone derived from the Michael addition of ascorbic acid to (E)-hex-2-enal, mixing the tricyclic hemiacetal lactone with the aqueous solution of citric acid, and applying heat. This confirmed that 6-propylbenzofuran-7-ol was formed via the Michael adduct.