Optimization and Validation of a Simple Method for Mineral Potential Evaluation in Citrus Residue

Abstract

The aim of this study was to optimize and validate a simple method for determination of the potential of important minerals for health (calcium, iron, zinc, and magnesium) in residue from orange and lemon juice industries and determine whether there are differences concerning these nutrients during the months when these fruits were harvested. The mineralization was optimized using an experimental design and then validated. Dried residue samples of Pera orange, Hamlin orange, Tahiti lime, Sicilian lemon, and a mixture composed of oranges and lemons were digested and analyzed by flame atomic absorption spectrophotometry (FAAS). Citrus fruit samples, harvested in different months, were also analyzed. The most appropriate condition for mineralization was the use of the highest values of sample mass (0.6 g) and nitric acid volume (8.0 mL). All the parameters of validation were met. The average mineral content levels found were 6.8 mg/g for calcium and 116.4, 915.5, and 7.4 μg/g for iron, magnesium, and zinc, respectively. Thus, a portion of 100 g of residue can provide 68.3% of the Recommended Daily Intake (RDI) for calcium, 35.2% for magnesium, 83.1% for iron, and 10.6% for zinc. The principal component analysis showed no clear separation among oranges, lemons, and the mixture as for their composition. The mineral content levels found indicate that citrus residue has nutritional potential for use in human food and can contribute significantly to the achievement of the RDIs, especially for calcium and iron, since their deficiencies are considered major public health problems.