Determination Of Mango And Orange Fruit Juice Quality By UV-Visible And Fluorescence Spectroscopy.

Abstract

In this study, the quality of mango and orange juices was determined using UVvisible and a fluorescence spectrophotometer. The juice were extracted with a home juice extractor. Subsequently the juice were filtered and each sample were separated in to three portions. Juices sample that were measured immediately marked as ’Fresh’ those stored at 220C for 8 days ( were marked as stored ) and the other portion heated-stored in a water bath at (400,600,800)C for 10 min. Results of Uv-visible absorption spectra of fresh mango juice were had peak at 455 nm . The absorption spectra of stored mango juice had peaks at 270 nm and 460 nm. The heated-stored at (400) mango juices had peak at 320 nm but no peaks found in heated-stored at 600 and 800C because this could be the effect of temperature dependence. The peak appearing at 270 nm corresponds to polymethoxyflavons. The peak at 460 nm corresponds to chlorophyll. The absorption spectra of fresh orange peaks at 330 nm and 390 nm . The stored orange juice had peaks at 260 nm and 320 nm. The absorption spectra peaks of heated-stored at 400C and 600C were found in 320 nm and 260 nm respectively, but no peaks at heated stored at 800C. The peak at 260 nm corresponds to vitamin C. The peak at 330 nm and 390 nm were assigned to cuomerin and vitamin A respectively. The emission spectra of fresh mango juice had peaks on 454 nm ,540 nm and 700 nm. The stored mango juice had peaks at 460 nm and 700 nm. Heated-stored mango juice at 400C have bands at 420-500 nm and peak at 700 nm. The heated-stored at 600C and 800C mango juice had peak only at 700 nm. The peak at 454 nm corresponds to total carotenoids. The emission spectra peaks at 546 nm and 700 nm corresponds to polymethoxyflavons and chlorophyll respectively. The emission spectra of fresh orange juice had peaks at 455 nm, 500 nm and 700 nm. The stored orange juice band around 460-500 nm and peak at 700 nm ,but heated-stored orange juice had peak only at 700 nm. The absecence of some absorption and fluorescence peaks in heated orange and mango juice above 400C indicated that essential vitamins in the sample were degraded, but heating also resulted in emergence of new peaks that could result from oxidation and heat solubility of vitamins. The pH value of mango and orange juice were 4.02-4.72,3.52-3.73 respectively. The effect of pH value of mango and orange juice on fluorescence spectra were differ from portion to portion of fruit samples. The fluorescence quantum yield of chlorophyll found in mango and orange juice were 0.10 and 0.37 respectively. The fluorescence lifetime value of two fruit juices were measured. The measured lifetime of two samples were 102.8 ms.