Novel Character Impact Compounds in Yuzu (Citrus junos Sieb. ex Tanaka) Peel Oil

Abstract

Yuzu ( Citrus junos Sieb. ex Tanaka), a tree-grown fruit similar to a kind of sour orange, is widely used in Japanese food/cooking for its pleasant flavor. To clarify the odor-active volatiles that differentiate yuzu from other citrus fruits, sensory evaluations were conducted on yuzu peel oil. The results revealed that the polar part of yuzu peel oil was the source of the characteristic aroma of fresh yuzu fruit. By aroma extract dilution analysis (AEDA) of the polar volatile part of yuzu peel oil, seven odorants were newly identified as odor-active volatiles in yuzu peel oil in the highest flavor dilution (FD) factors of 128 and 32: oct-1-en-3-one, (E)-non-4-enal, (E)-dec-4-enal, 4-methyl-4-mercaptopentan-2-one, (E)-non-6-enal, (6Z,8E)-undeca-6,8,10-trien-3-one (Yuzunone), and (6Z,8E)-undeca-6,8,10-trien-4-ol (Yuzuol). Among the most odor-active volatiles in yuzu, (E)-non-6-enal and Yuzunone were identified for the first time solely in yuzu peel oil and not in the peel of other citrus species, and Yuzuol was identified for the first time in nature. Sensory evaluation of yuzu aroma reconstitutions revealed that the newly identified compound, Yuzunone, contributes greatly to the distinct yuzu aroma.

Aroma Character Impact Compounds in Kinokuni Mandarin Orange (Citrus kinokuni) Compared with Satsuma Mandarin Orange (Citrus unshiu)

“…The following compounds were purchased from commercial sources: hexanal, (Z)-hex-3-enal, 1,8-cineole, octanal, (Z)-hex-3-en-1-ol, nonanal, 2-isopropyl-3-methoxypyrazine, acetic acid, citronellal, decanal, (E)-non-2-enal, linalool, undecanal, (E)-dec-2-enal, dodecanal, (E)-undec-2-enal, citronellol, perillaldehyde, (2E,4E)-deca-2,4-dienal, geraniol, (E)-dodec-2-enal, eugenol, thymol, isothymol, indole, -pinene, myrcene, limonene, -terpinene, isoamyl alcohol, oct-1-en-3-one, (E)-hept-2-enal, (E)-oct-2-enal, benzaldehyde, (2E,6Z)-nona-2,6-dienal, 2-methylbutanoic acid, 2-acetyl-2-thiazoline, 2-phenylethanol, 4-hydroxy-2,5-dimethylfuran-3(2H)-one, methyl Nmethylanthranilate and vanillin (Sigma-Aldrich Japan, Tokyo, Japan); -damascenone (Firmenich, Meyrin, Switzerland); a mixture of 2-ethyl-4-hydroxy-5-methylfuran-3(2H)-one and 5-ethyl-4-hydroxy-2-methylfuran-3(2H)-one (Givaudan, Vernier, Switzerland); and tridec-1-ene (Tokyo Chemical Industry Co., Tokyo, Japan). The following compounds were synthesized by the methods reported in the literature: (3E,5Z)-undeca-1,3,5-triene, 26) (3E,5Z,8Z)-undeca-1,3,5,8-tetraene, 27) 6-methylheptanal, 28) 6-methyloctanal, 28) yuzunone ((6Z,8E)-undeca-6,8,10-trien-3-one), 29) yuzuol ((6Z,8E)-undeca-6,8,10-trien-4-ol), 30) (2E)-cis-4,5-epoxydec-2-enal, 31) (2E)-trans-4,5-epoxydec-2-enal, 32) (2E,7Z)-trans-4,5-epoxydeca-2,7-dienal 33) and wine lactone (3,6-dimethyl-3a,4,5,7a-tetrahydro-1-benzofuran-2(3H)-one). 34,35) All reagents and solvents were of analytical grade.…”

“…Seven attributes of fruity, sweet, floral, green, metallic, sour, and balsamic were used. These attributes had been previously selected by our laboratory to provide a suitable vocabulary for describing the aroma of citrus fruits 30) that is commonly used for sensory evaluations.…”

“…Since the preliminary experiments revealed the excessive presence of monoterpene hydrocarbons in the peel oil that prevented the identification and determination of small peaks on GC which might have some contribution to the odor of the samples, 30) the Kinokuni and Satsuma mandarin peel oils were fractionated by silica gel chromatography into two parts, a nonpolar fraction abundant in hydrocarbons and a polar fraction abundant in oxygenated compounds. The weight ratio of the fractionated polar components was almost double in Kinokuni mandarin (1.9) than that in Satsuma mandarin (1.0) ( Table 1).…”

Polymethoxyflavones, Synephrine and Volatile Constitution of Peels of Citrus Fruit Grown in Okinawa

“…Compounds that could not be identified by comparison to authentic standards were identified on the basis of results in the FFNSC and NIST08 libraries (Shimadzu Co.) and the retention index calculated using the retention time of co-injected n-alkanes. We also referred to previously published retention indexes of volatile citrus components (Akakabe et al, 2008a, b;Belsito et al, 2007;Choi andSawamura, 2001, 2002;Fanciullino et al, 2006;Gariele et al, 2009;Miyazawa et al, 2009;Phi et al, 2006Phi et al, , 2009.…”

High‐impact odorants in essential oils

“…The high price or scarcity of the natural oil is often the driver behind this work, but it can also simply be the search for new aroma compounds that impart the recognizable character of the natural oil. This applies equally in both fl avour and fragrance research and over time has led to the discovery of some important materials used in the fl avour and fragrance industry, such as the thio-esters in galbanum, [1] oxane from passion fruit, [2] grapefruit thiol [3] and 3-hexylpyridine from orange, [4] and continues to date with the discovery of Yuzuol [(6Z,8E)-undeca-6,8,10-trien-4-ol] [5] and (Z)-4-hepten-2-yl salicylate ( Figure 1). [6,7] The principal analytical technique used in the determination of odorants in essential oils is gas chromatography-olfactometry (GC-O), which is as old as the science of gas chromatography (GC) itself, since early experiments in GC involved smelling the effl uent from the column to detect the analytes.…”