Optimization and Validation of a Simple Method for Mineral Potential Evaluation in Citrus Residue Joyce Grazielle Siqueira Silva 1 & Eduardo Adilson Orlando 1 & Ana Paula Rebellato 1 & Juliana Azevedo Lima Pallone 1 Received: 12 September 2016 /Accepted: 6 December 2016 # Springer Science+Business Media New York 2016 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 dur- ing the months when these fruits were harvested. The miner- alization 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 indi- cate that citrus residue has nutritional potential for use in hu- man food and can contribute significantly to the achievement of the RDIs, especially for calcium and iron, since their defi- ciencies are considered major public health problems. Keywords Iron . Calcium . Zinc . Magnesium . Experimental design . Lime Introduction The production of citrus fruits (orange/lemon) is one of the most important sectors of Brazilian agribusiness, with annual harvest of approximately 18 million tons of orange, which corresponds to 30% of the world production; 80% of the Brazilian production is intended for the juice industry (IBGE 2014; MAPA 2015). The lemon production is over 1 million tons, and the state of São Paulo accounts for most of the citrus produced in the country (IBGE 2014). In addition to juice, essential oils from peel, aromatic liq- uid, bran, and residue are generated from orange and lemon processing. Citrus residue is used in the composition of animal feed (Munhoz and Morabito 2010); it may also be used as coal for generation of energy (Rezzadori and Benedetti 2009). Some studies assess the use of orange and lemon residue as biomass for production of biogas, bioethanol, and bioenergy as a way to reduce the environmental impact caused by the disposal of such residue on the environment (Bożym et al. 2015; Choi et al. 2015; Vamvuka et al. 2014). Citrus residue has been used in fermentation processes for the production of enzymes, for the degradation of substances (Júnior et al. 2012), and for obtaining bioactive phenolics (Júnior et al. 2014). The fibers of some citrus were studied as potential functional ingredients in foods like ice cream, cookies, and cereal bar, undergoing evaluation as for physicochemical and technological properties (López-Marcos et al. 2015; Santos et al. 2011). The composition of citrus peel may vary depending on cultivar, fruit ripeness, climate, type of soil, and fertilization. Barros et al. (2012) reported that Pera orange and Tahiti lime * Juliana Azevedo Lima Pallone jpallone@unicamp.br 1 Department of Food Science, School of Food Engineering, University of Campinas, Monteiro Lobato Street, 80, Campinas, SP 13083-862, Brazil Food Anal. Methods DOI 10.1007/s12161-016-0748-3