Flavonoid contributors to bitterness in juice from Citrus and Citrus hybrids with/without Poncirus trifoliata in their pedigree

Authors: Jeffries, Kristen; FAN, ZHEN - University Of Florida; Mattia, Matthew; Stover, Eddie; Baldwin, Elizabeth; Manthey, John; Breksa Iii, Andrew; Bai, Jinhe; Plotto, Anne

Submitted to: Food Chemistry: X
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/15/2025
Publication Date: 2/18/2025
Citation: Jeffries, K.A., Fan, Z., Mattia, M.R., Stover, E.W., Baldwin, E.A., Manthey, J.A., Breksa Iii, A.P., Bai, J., Plotto, A. Flavonoid contributors to bitterness in juice from Citrus and Citrus hybrids with/without Poncirus trifoliata in their pedigree. Food Chemistry: X. 26:102289. 2025. https://doi.org/10.1016/j.fochx.2025.102289.
DOI: https://doi.org/10.1016/j.fochx.2025.102289

Interpretive Summary: Breeding citrus trees that are tolerant to the devastating Huanglongbing (HLB) disease has been a priority in recent years. However, citrus fruits may exhibit a wide range of flavors, including mild to unacceptably high levels of bitterness. There is still a gap in the knowledge of bitterness inducing compounds in citrus, due to the complexity of flavonoids that contribute to taste. In this study, we used a diverse sample of citrus fruit showing a range of bitterness (low to extreme) by taste. An in-depth analysis of volatile and non-volatile compounds was performed, and some compounds not previously reported being bitter were found in this study. The knowledge of the chemistry of bitterness will help breeders to select fruit with acceptable eating quality.

Technical Abstract: In the Huanglongbing (HLB) era, the quality of citrus juice has declined, resulting in undesirable off-flavors and increased bitterness. Additionally, bitterness and off-flavors are problematic in some HLB-tolerant genotypes, such as Citrus hybrids with Poncirus trifoliata in their pedigrees. Comprehensive chemical profiling combined with sensory analysis of bitterness were used to determine bitter compounds in citrus juice, other than the well-known contributors, such as the limonoids, limonin and nomilin, and the flavonoid naringin. A diverse selection of genotypes including orange, grapefruit, pummelo, tangelo, mandarin hybrids with and without P. trifoliata in their pedigrees, as well as pure P. trifoliata, were analyzed due to their broad range in bitter intensity. Given reports that volatile compounds can affect taste, both volatile and non-volatile components were analyzed. The volatile compounds camphene, trans-alloocimene, '-muurolene, and d-elemene were positively correlated with bitterness while esters were negatively correlated with bitterness. Widely targeted LC-MS/MS analysis of flavonoids and limonoids confirmed the role of limonin, nomilin, neohesperidin and poncirin in bitterness perception, as indicated by their correlations with sensory data. Other flavonoids, mainly rhoifolin, apigenin, and tricin also correlated with bitterness. Notably, rhoifolin was more strongly correlated with bitterness than the previously known bitter compounds. Identifying the compounds that contribute to bitterness in citrus is a crucial first step for future breeding efforts aimed at reducing these compounds biosynthetically. These data could also be useful in making debittering technologies more targeted and effective.