Abstract
Citric acid is the most abundant organic acid present in fruits and is involved in influencing the taste, acidic properties, nutritional value, and preserving features. Quantitation of citric acid is vital in evaluating food quality, nutritional status, and analysis in pharmaceuticals. Though there are sophisticated analytical methods which yield accurate results, such as chromatography, their applicability can be hindered due to cost implications. The current experiment sought to establish the use of a rapid, cheap, and reliable method of UV-visible spectroscopy in the quantitation of citric acid in selected fruits and its relation to pH. Samples of lemon (Citrus limon), orange (Citrus sinensis), amla (Phyllanthus
emblica), pineapple (Ananas comosus), and tomato (Solanum lycopersicum) were subjected to the tests. Fruit extracts were prepared through a maceration method followed by filtration and centrifugation. A calibration curve was drawn from standard citric acid solution while UV-visible spectrophotometric analysis was performed using the wavelength of maximum absorption (λmax). Quantification was done at 210 nm using Beer-Lambert law. The pH of the fruits was measured in relation to citric acid. Based on the spectral results, the wavelength of maximal absorption was found to be 210 nm for citric acid. The calibration plot indicated linear relationship with R2 value of 0.9997, indicating that the proposed method is applicable for quantitative analysis. Comparing fruits for their citric acid concentrations, lemon has been found to contain the highest amount while tomato contains the lowest amount. The Pearson correlation test showed that there is high negative correlation between pH and citric acid concentration (r=−0.987). The proposed UV-Visible spectrophotometric method has been successfully used as an efficient, simple, and cost-effective technique for the determination of citric acid in various fruits.