Analytical Methods Analysis of bakery products by laser-induced breakdown spectroscopy Gonca Bilge a , _ Ismail Hakkı Boyacı a,b,⇑ , Kemal Efe Eseller c , Ug ˘ur Tamer d , Serhat Çakır e a Department of Food Engineering, Hacettepe University, Beytepe, 06800 Ankara, Turkey b Food Research Center, Hacettepe University, Beytepe, 06800 Ankara, Turkey c Department of Electrical and Electronics Engineering, Atilim University, 06836 Ankara, Turkey d Department of Analytical Chemistry, Faculty of Pharmacy, Gazi University, 06330 Ankara, Turkey e Department of Physics, Middle East Technical University, 06800 Ankara, Turkey article info Article history: Received 16 October 2014 Received in revised form 14 January 2015 Accepted 17 February 2015 Available online 24 February 2015 Keywords: Laser-induced breakdown spectroscopy (LIBS) Bakery products Detection of NaCl Detection of Na Titration Atomic absorption spectroscopy (AAS) abstract In this study, we focused on the detection of Na in bakery products by using laser-induced breakdown spectroscopy (LIBS) as a quick and simple method. LIBS experiments were performed to examine the Na at 589 nm to quantify NaCl. A series of standard bread sample pellets containing various concentra- tions of NaCl (0.025–3.5%) were used to construct the calibration curves and to determine the detection limits of the measurements. Calibration graphs were drawn to indicate functions of NaCl and Na concen- trations, which showed good linearity in the range of 0.025–3.5% NaCl and 0.01–1.4% Na concentrations with correlation coefficients (R 2 ) values greater than 0.98 and 0.96. The obtained detection limits for NaCl and Na were 175 and 69 ppm, respectively. Performed experimental studies showed that LIBS is a convenient method for commercial bakery products to quantify NaCl concentrations as a rapid and in situ technique. Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction 70–75% of the total sodium chloride (NaCl) intake in the human diet is obtained from processed foods (James, Ralph, & Sanchez Castillo, 1987), out of which cereal and cereal products constitute approximately 30% (FSAI, 2005). Hence, reducing the NaCl content in bakery products could decrease the overall NaCl intake in human diet. Since a large number of deaths related to excessive salt intake are due to the consumption of bread with high NaCl contents , this quantity must be reduced (He & MacGregor, 2007). Moreover, studies have shown that excessive dietary Na intake increases blood pressure (Elliott et al., 1996) and may cause strokes (Xie, Sasaki, Joossens, & Kestelool, 1992) and coronary heart diseases (Tuomilehto et al., 2001). However, many bakers are reluctant to reduce the salt content in bread because it may lead to insufficient dough strength and undesirable sensory profiles. NaCl is an impor- tant ingredient in bakery products as it contributes to the dough- making process by regulating the fermentation rate, strengthening the dough and adding to the taste of the bread (Salovaara, 1982). In addition, NaCl is a quality control indicator in bakery prod- ucts. The NaCl level in foods should adhere to Codex Alimentarius standards. Therefore, NaCl detection is critical in bakery products. Several methods are used to determine the NaCl content in bakery products. Some of these methods are based on the presence of Na ions, whereas others are based on that of Cl ions (Plácido et al., 2012). The potentiometric method, which utilizes ion selective Na or Cl electrodes, is most widely used to determine the amount of salt in food products. Other commonly used methods include titration to determine Cl levels and flame atomic absorption spec- trometry to determine Na content (Capuano et al., 2013; Smith & Haider, 2014). These methods are time consuming, and their appli- cation procedures are difficult. They also require sample prepara- tion, which makes them unsuitable for in situ and point detection analyses. Therefore, laser-induced breakdown spec- troscopy (LIBS) has emerged as a valuable tool for quick and in situ analyses (Choi, Lee, & Yoh, 2013; Singh et al., 2008). LIBS is an optical emission spectroscopy technique based on laser-produced plasma, in which a laser beam excites and intensively heats a small volume of the sample. The heated sample is taken to a gaseous plasma state and is broken down into atoms, which produces a characteristic light. This light is analyzed spectrally; and through calibration, the intensity of the spectra indicates the concentration of the elements in the sample (St-Onge et al., 2004). http://dx.doi.org/10.1016/j.foodchem.2015.02.090 0308-8146/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author at: Food Research Center, Hacettepe University, Beytepe, 06800 Ankara, Turkey. Tel.: +90 312 297 61 46; fax: +90 312 299 21 23. E-mail addresses: goncabilge@yahoo.com.tr (G. Bilge), ihb@hacettepe.edu.tr ( _ I.H. Boyacı), efe.eseller@atilim.edu.tr (K.E. Eseller), utamer@gazi.edu.tr (U. Tamer), cakir@metu.edu.tr (S. Çakır). Food Chemistry 181 (2015) 186–190 Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem