Rapid and Simultaneous Measurement of Organic Acids and Amino Acids in Cheddar Cheese Using Spectroscopy
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Date
2009-03-31T17:49:51Z
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Abstract
The flavor of Cheddar cheese influences its acceptance, price and application. Organic acids and amino acids are important flavor compounds and hence their quantification is essential. Chromatographic methods are complicated, time-consuming, and expensive. The potential of using Fourier transform infrared (FTIR) spectroscopy to rapidly and simultaneously measure organic acids and amino acids was investigated.
Twelve different Cheddar cheese samples were sampled on days 7, 15, 30, 45 and 73 during ripening and the water soluble compounds were extracted using organic solvents. The extracts were analyzed by reverse phase liquid chromatography for 3 organic acids, gas chromatography for 15 amino acids, and FTIR to collect the spectra (4000-700 cm-1). The organic acid and amino acid concentrations were correlated with the FTIR spectra and analyzed by multivariate regression analysis to build prediction models.
The developed models showed excellent fit with coefficient of correlation >0.95 and could simultaneously determine the levels of organic acids and amino acids in cheese samples in less than 20 min. The estimated standard errors for predicting unknown samples were less than 4%. Absorptions from organic acids and amino acids (1800-900 cm-1) were found to be very important factors influencing the PLS models. Lactic acid, glutamic acid, leucine, asparagine, phenylalanine and valine are some of the compounds that exhibited significant changes during ripening.
This method shows great promise as a rapid analytical tool for simultaneous determination of organic acids and amino acids in cheese. It can save time, labor and operational costs for the industry and cheese research.
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Infrared Spectroscopy, Cheddar Cheese, Amino Acids, Organic Acids