Submitted to: Journal of Agriculture and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/4/2010
Publication Date: 3/25/2010
Citation: Chen, P., Harnly, J.M., Lester, G.E. 2010. Flow injection mass spectral fingerprints demonstrate chemical differences in Rio Red grapefruit with respect to year, harvest time, and conventional versus organic farming. Journal of Agriculture and Food Chemistry. 58(8):4545-4553.
Interpretive Summary: Samples of Rio Red grapefruit (citrus paradisi) grown using conventional and organic cultivation methods at three distinct growing phases (early, mid, and late season harvest) during two sequential years (2005 and 2006) were collected and analyzed using two methods for mass spectrometry (MS) to get their MS spectral fingerprints. A special way of analyzing the data (analysis-of-variance principal-component-analysis) was performed to determine if a distinction could be made between the two cultivation methods and the three harvest dates (growing phases) by analyzing the MS spectral fingerprints. The chemical patterns of the fingerprints were statistically different depending on farming mode, growing year, and time of harvest, regardless of the method of MS used. This information is of use to consumers and regulators because it provides a rapid method to discriminate between not only time of harvest, but also conventional versus organic farming mode, important in validating claims when organic products are marketed.
Technical Abstract: Spectral fingerprints were acquired for Ruby Red grapefruit using direct injection-electrospray ionization with time-of-flight and ion trap mass spectrometry (DI-ESI-TOF-MS and DI-ESI-IT-MS). Rio Red grapefruits were harvested 3 times a year (early, mid, and late harvests) in 2005 and 2006 from conventionally and organically grown trees. Data analysis using analysis of variance-principal component analysis (ANOVA-PCA) demonstrated that, for both MS systems, the chemical patterns were different as a function of farming mode (conventional vs organic), as well as growing year and time of harvest. This was visually obvious with PCA and was shown to be statistically significant using ANOVA. The spectral fingerprints provided a more inclusive view of the chemical composition of the grapefruit and extended previous conclusions regarding the chemical differences between conventional and organic grown Red Rio graperfruit.