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Diacetyl (2,3-butanedione), a buttery flavored compound made during beer production, is formed from α-acetolactate via oxidative decarboxylation. Current analytical methods to detect diacetyl are time-consuming and expensive; however, measurements of carbon dioxide can be rapid and inexpensive. Attenuated total reflectance–Fourier transform infrared spectroscopy (ATR-FTIR) utilizing a flow cell and mid-range infrared energy (400 cm-1 – 4000 cm-1) is capable of measurements for dissolved CO2. An ATR-FTIR system was constructed using a Ge flow cell, an HPLC pump, and stainless-steel tubing. A method for analyzing a model reaction compared to a natural process in fermentation was developed. Exploring the effects of the different matrices provided a useful analytical tool. The limit of detection for CO2 was found to be as low as 22.5 ppm and the limit of quantification as low as 74.9 ppm. Concentrations of dissolved CO2 can be determined using the peak area or height of the asymmetric C=O signal at =2349 cm-1. A rate study of the decarboxylation reaction with ethyl acetoacetate revealed that the energy of activation was calculated for a pseudo-first-order decarboxylation of the model reaction was determined to be 54.1 kJ/mol.

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