ESR as a testing tool for the oxidation performance of beer, it can monitor the changes of free radicals in beer brewing process, predict the flavor preservation period, and evaluate the beer flavor stability.
The determination of the Endogenous Antioxidative Potential (EAP) and the Beverage Antioxidative index(BAX) using Electron Spin Resonance Measurements(ESR) is an ideal tool for the evaluation of the beer’s oxidative flavor stability and shelf time. The benchtop ESR Spectrometer MS 5000 along with the novel Autosampler unit allows a fully automated measurement of these values.
Fully automated handling of samples
Up to 30 samples per analysis
Temperature control up to 70°C
Automatic EAP and BAX calculation
State-of-the-art and user friendly software
Beer Analysis Technique
Due to the chain reaction of beer-derived free radicals, carbonyl end products like aldehydes and ketones are created,which cause the staling of beer. However, the endogenous antioxidants inhibit the free radical oxidation until they are depleted. Hence this free radical oxidation can be minimized by optimizing brewery operations and storage conditions to provide maximum antioxidant content on the packaged beer
At each stage of the brewing process the comprehensive antioxidant status of the beer can be determined by ESR measurement and the determination of the EAP- and BAX value.In this way, the shelf life and flavor stability of a finished beer can be determined at the initial stages of brewing process i.e. before packaging and distribution.
ESR EAP and BAX evaluation
The EAP measurement is based on the indirect detection of the radical generation in beer during accelerated beer ageing at raised temperatures (60 °C). The formed short-lived reactive radicals can be monitored by trapping them with spin trap reagents (POBN) and the detection of the long-lived spin trap adducts using the MS 5000 Bench-Top ESR spectrometer.For a certain period of time, the radical generation is delayed or prevented by the beer’s endogenous anti-oxidative activity (lag-phase). After the lag phase the amount of spin adducts begins to increase rapidly. The EAP value is a measure for the duration of the lag phase and hence a beer with a high EAP value has a long flavor stability and vice versa.
Figure 1 demonstrates such an EAP determination of beer after the addition of different amounts of SO2. The novel EAP value is linear dependent of the SO2 content (Fig. 2) and offers a new beneficial index number for the evaluation of the flavor stability; the so called Beverage Antioxidative index (BAX). The BAX provides additional information about the anti and prooxidative properties of the beer matrix regardless of the SO2 content and gives information of the consumption rate of the existing Antioxidative potential during storage.With the MS 5000, its Autosampler unit and the comprehensive software both values (EAP and BAX) can be measured fully automated and with high precision.
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