Application of Laser-Induced Breakdown Spectroscopy Technique for Studying Salt Diffusion in Model Cheese Matrices

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Journal/Book Title/Conference

American Dairy Science Association 2020 virtual annual meeting



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Salt dissolved in the aqueous phase of cheese, plays vital roles during cheese manufacture by manipulating protein-protein and protein-water interaction and during ripening by contributing to the flavor of cheese, controlling the growth of microorganisms, and helping with enzymatic breakdown of cheese. Salt diffusion in the cheese moisture phase is a slow process. Conventional methods used for tracking salt migration within cheese matrices involve wet chemistry, tedious sample preparation and longer estimation times. Laser-induced breakdown spectroscopy (LIBS) is a novel technique which is currently used for mineral analysis in different food materials. The technique gives spatial distribution (at macroscopic level) of minerals (Na, K, Ca) on a surface; it requires no sample preparation; it is a non-invasive and quick method and it doesn't involve hazardous chemicals and procedures. The current work examined the ability of LIBS technique to capture sodium/salt migration in cheese systems. Cheese samples with different contact time (0, 30, 60 min) with brine (23%) solution were cut into half cubes (2.5x2.5x2.5 cm3). Spatially distributed LIBS spectra were collected from interior cut surfaces/cross sections by applying laser shots in 45x45 square grid patterns. The emission peaks of plasma light at 589.05, 393.339 and 769.826 nm in each spectral data moment were used to generate sodium, calcium and potassium distribution images, respectively. A clear difference in spatial distribution of Na was observed in the control as compared with brined model cheeses dipped for 30 and 60 min. With brining time, the relative area of pixels indicating higher Na concentration levels increased significantly. Progressive diffusion of salt within model cheese matrix was clearly evident in spatial distribution mapping plots for Na. This work highlights a novel application of LIBS technique for generating spatially distributed salt concentration maps within cheese matrices. This technique may be applied for studying salt diffusion kinetics.

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