Application of quantitative nuclear magnetic resonance spectroscopy to biological acidification of barley mashes

Abstract

Spontaneous biological acidification has long been a part of the German brewing tradition, and was historically used to optimize the pH of brewhouse mashes. By facilitating the growth of native barley flora, the production of lactic, acetic and succinic acids sours the mash, functioning in a similar way to the addition of food-grade acids, which are prohibited under the Reinheitsgebot of 1516. Traditionally, sour mashes have been performed at the 'optimum' temperature of 49°C. Quantitative proton nuclear magnetic resonance spectroscopy was used for the investigation and quantitation of organic acids produced by acidified mashes over a range of temperatures. All target metabolites demonstrated an inverse relationship with temperature, although lactic acid reached a relative maximum at 49°C, which is in agreement with the customary sour mash temperature. Therefore, it would seem that the optimization of a sour mash is dependent not on absolute acid concentration, which would give the greatest pH regulation potential, but on the relative acid concentration, an important factor influencing the final flavour profile of a beer.

Gas chromatography-mass spectrometric determination of organic acids by ion pair liquid extraction followed by in-situ butylation from aqua feed samples

“…Several studies were previously reported to identify and quantify the OAs in various food and beverage samples 13 and environmental matrices. 14 Different analytical techniques including Ion exclusion chromatography (IEC), 15 Capillary electrophoresis (CE), 16 Nuclear magnetic resonance (NMR) spectroscopy, 17 High performance liquid chromatography (HPLC), 18 LC-MS, [19][20][21] Gas chromatography-mass spectrometry (GC-MS) 13,22 have been applied for the quantification of OAs from food products. Among all the techniques, the GC-MS technique has certain advantages such as low equipment cost, little solvent requirement, ease of analysis, and data reproducibility.…”