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Identification of Bitter Compounds in Raw American Hazelnuts

Wang, Xue
http://rave.ohiolink.edu/etdc/view?acc_num=osu1610062397743891

Abstract Details

2021, Doctor of Philosophy, Ohio State University, Food Science and Technology.
As the second most popular tree nuts in the world, hazelnuts are widely used as key ingredients in the bakery, chocolate, and snack market, with global production of more than 528,000 metric tons in 2019-2020. With the increasing global demand of hazelnuts, US hazelnut producers are developing commercial American hazelnuts (C.Americana) to support the local market. However, American hazelnuts are considered to have inferior flavor quality, including increased bitterness, compared to European hazelnuts. One of the main product attributes that influence food choice is flavor quality. Therefore, an improved understanding of the molecular basis for the lower flavor quality of American hazelnuts is needed for commercial success. The overall aim of this project was to characterize the compounds that contribute to aversive bitterness in raw American hazelnuts. Initial sensory screening of a subset of American hazelnut varieties grown in the Midwest indicated bitterness was a main off-flavor present in the raw nuts. Compared to European varieties, less is known regarding the chemical drivers of bitterness formation in American hazelnuts, hindering the development of high flavor quality American hazelnuts. A targeted sensory-guided multi-dimensional Liquid Chromatography / Mass Spectrometry (LC-MS) fractionation approach was used to select compounds contributing to the bitterness in native American hazelnuts (C. americana). Accurate MS - QTof and mono- and bidimensional Nuclear Magnetic Resonance (NMR) spectroscopy were used to identify compounds responsible for bitterness in the selected fractions. Four bitter compounds were identified and reported for the first time in American hazelnuts, including Carpinontriol B (compound 1), 2-(3-hydroxy-2-oxoindolin-3-yl)acetic acid 3-O-6’-galactopyranosyl-2”-(2”oxoindolin-3”yl) acetate (compound 2), Giffonin 2-O-[(α-D-glucopyranosyl)-6′-O-(3-hydroxy-3-methylglutaric acid)] (compound 3), and Kaempferol-3-rhamnoside (compound 4). Their sensory impact was further evaluated by determining the sensory recognition threshold for each compound. The bitter recognition thresholds for compounds 1, 2, 3 and 4 were 1.5, 234.3, 6.1, and 19.7 mg/kg, respectively. The concentrations of the bitter compounds were further quantified in the American hazelnuts and across the 88 American hybrid hazelnuts. Only compound 1 in the American hazelnut was reported to be above the threshold value, however, the concentrations of compounds 1, 2, and 3 were determined to be above the bitter recognition threshold values for 96%, 75%, and 25%, respectively of the 88 hybrid hazelnut samples. Additionally, the levels of compounds 1 and 3 can be degraded significantly under forced air drying at 50℃, providing opportunities to optimize post-harvest processing. In summary, four aversive endogenous bitter compounds were reported for the first time in C. americana hazelnuts. The identified bitter compounds provide molecular targets for US hazelnut producers to improve the flavor quality by breeding and postharvest handling strategies to improve consumer liking and commercial success.
Devin Peterson (Advisor)
120 p.
Food Science

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Citations

  • Wang, X. (2021). Identification of Bitter Compounds in Raw American Hazelnuts [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1610062397743891

    APA Style (7th edition)

  • Wang, Xue. Identification of Bitter Compounds in Raw American Hazelnuts. 2021. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1610062397743891.

    MLA Style (8th edition)

  • Wang, Xue. "Identification of Bitter Compounds in Raw American Hazelnuts." Doctoral dissertation, Ohio State University, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=osu1610062397743891

    Chicago Manual of Style (17th edition)

osu1610062397743891
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