Submitted to: Proceedings of Symposium Fertilizing Crops for Functional Foods
Publication Type: Proceedings
Publication Acceptance Date: 11/1/2002
Publication Date: 11/1/2003
Citation: PATIL, B.S., ALVA, A.K. FUNCTIONAL COMPONENTS IN CITRUS: ALTERATION BY MINERAL ELEMENTS. PROCEEDINGS OF SYMPOSIUM FERTILIZING CROPS FOR FUNCTIONAL FOODS, PP. 44-50. 2003. Interpretive Summary: The health benefits of fruits and vegetables are due to the presence of phytonutrients. Grapefruit contains carotenoids, flavanones, limonin glucopyranoside, and vitamin C, which are known to prevent and/or reduce the risk of cancer and cardiovascular disease. The production management factors influence the levels of some functional compounds were investigated. In this study, effects of different rates of potassium additions to grapefruit trees on the content of functional compounds. The treatments included application of 0, 93, 140, 186, and 233 kg/ha K. In order to maintain 1:1 ratio of N:K2O, N was also varied at 0, 112, 168, 224, and 280 kg/ha, respectively. The concentration of naringin decreased significantly in fruits sampled from trees which received the highest K rate as compared to that in the no K amended treatment. The contents of beta carotene, lycopene, and vitamin C were not influenced by different rates of fertilization. Increased rates of K application decreased ascorbic acid content, while increased dehydroascorbic acid content.
Technical Abstract: Grapefruit functional compounds such as carotenoids, flavanones, limonin 17-b-D glucopyranoside (LG), and vitamin C have been shown to have potential human health benefits including cancer and cardiovascular disease prevention. This study was conducted to determine different levels of potassium (K) on functional compounds. Field and laboratory studies were conducted at the University of Florida, Citrus Research and Education Center (CRES) in Lake Alfred, FL and Texas A&M University-Kingsville Citrus Center (TAMUK-CC) in Weslaco, TX, respectively. `Ray Ruby¿ grapefruits on Carrizo citrange rootstock were harvested from a N and K rate effect study conducted in CREC and shipped to TAMUK-CC. Fifteen fruits each from three replications per treatment were stored. Reverse phase high performance liquid chromatography was used to quantify the functional compounds. The highest levels of N/K rate significantly decreased naringin concentration compared that of fruits sampled from the tree which received no supplemental N or K. Although there was no significant differences in levels of beta carotene and lycopene due to different levels of K applied, total carotenoids levels were significantly higher in control fruits compared to that in the fruits from 186 kg K/ha treatment. Higher levels of K application decreased ascorbic acid while increased dehydroascorbic acid concentration as compared to those in the fruits from N and K unamended treatment. Total vitamin C concentration was not significantly influenced by different levels of K. Grapefruits sampled from the trees which received 93 kg K/ha had significantly lower LG concentrations compared to that of the fruits in the N and K unamended treatment. Since this study was conducted with variable rates of both N and K, further studies with variable rate of single elements are necessary to understand the effects of each element on the phytonutrient contents in the fruits.