Volatile and nonvolatile flavor chemical evaluation of USDA orange-mandarin hybrids for comparison to sweet orange and mandarin fruit

Authors: Bai, Jinhe; Baldwin, Elizabeth - Liz; DRIGGERS, RANDALL; HEARN, JACK - RETIRED ARS EMPLOYEE; STOVER, EDDIE

Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/31/2016
Publication Date: 7/31/2016
Citation: Bai, J., Baldwin, E.A., Driggers, R.E., Hearn, J., Stover, E.W. 2016. Volatile and nonvolatile flavor chemical evaluation of USDA orange-mandarin hybrids for comparison to sweet orange and mandarin fruit. Journal of the American Society for Horticultural Science. 141(4):339-350.

Interpretive Summary: This research evaluated three citrus hybrids for their qualification as "sweet orange", based on their aroma profile. Volatile profile and key aroma contributor comparisons alone and with cluster analysis were used for classification of three new citrus hybrids. FF-1-74-52 was essentially indistinguishable from sweet orange, while FF-1-75-55 and FF-1-76-52, each had some similar flavor attributes to sweet orange. The research provided critical information for the USDA sweet orange breeding program.

Technical Abstract: Three citrus hybrids, containing 50-75% sweet orange (Citrus sinensis) genome in their pedigrees and similar to sweet orange in fruit size, color and taste, were tested for their potential to be classified as new “sweet orange” cultivars. 'Hamlin', ‘Midsweet’, and three other early to mid-season sweet orange cultivars, along with ‘Dancy’ (C. reticulata), a typical mandarin, were used for comparison. Fruits were picked on Jan. 23, 2014, Dec. 30, 2014 and Jan. 27, 2015. A total of 114 volatiles were detected and separated into 7 groups by detection frequency: 3 groups with 43 volatile components did not show differences and had little information in classification of sweet orange from mandarin, and the remaining 4 groups with 71 volatiles contributed to distinctions between orange and mandarin. Among the hybrids, the pattern of volatile detection frequency in hybrid FF-1-74-52 was virtually identical to sweet orange, and cluster analysis agreed with the classification. The number of average peaks were 55-62 in sweet oranges, 67 in FF-1-74-52, and 17-37 in tangerine and other hybrids. Quantity analysis of individual volatiles and chemical classes indicated that, FF-1-74-52 and sweet oranges were rich in total volatile abundance, and almost all chemical classes including mono and sesquiterpenes, aldehydes, alcohols, ketones and esters. This was especially true for ethyl butanoate, which contributes a fruity top-note, and valencene and all sesquiterpene hydrocarbons, which only contribute to citrus flavor indirectly through their contribution to headspace partitioning. Two other hybrids, FF-1-75-55 and FF-1-76-51, each had some similarity to sweet oranges in several chemicals and classes, but not in the overall volatile profile. All three sweet-orange-like hybrids met the standards for mandarins and oranges in soluble solids contents (SSC), titratable acidity (TA) and SST/TA ratio. The above volatile and non-volatile flavor chemical profile comparisons strongly support a proposal to classify FF-1-74-52 as a ‘sweet orange’ commercially, and all three hybrids were previously shown to be more similar to sweet orange in their volatile profile than is ‘Ambersweet’. ‘Ambersweet’ was a hybrid that was legally classified as a sweet orange in 1995 based on its volatile profile.