Lehrstuhl für Lebensmittelchemie und Molekulare Sensorik, Wissenschaftszentrum Weihenstephan für Ernährung, Landnutzung und Umwelt, Technische Universität München, D-85354 Freising, Germany.
Institut für Lebensmitteltechnologie und Lebensmittelchemie, Fachgebiet Brauwesen, Technische Universität Berlin, D-13353 Berlin, Germany.
J Agric Food Chem. 2021 Aug 18;69(32):9443-9450. doi: 10.1021/acs.jafc.1c03018. Epub 2021 Aug 5.
Styrene is a food-borne toxicant in wheat beer and due to its classification as possibly carcinogenic to humans by the International Agency for Research on Cancer in 2002, mitigation strategies had to be developed. Aiming at understanding the impact of the barley to wheat malt ratio (grain bill) during mashing on the contents of soluble and free (i) cinnamic, (ii) -coumaric, and (iii) ferulic acid, precursors of (i) styrene and the desired vinyl aromatics (ii) 4-vinylphenol and (iii) 2-methoxy-4-vinylphenol in wheat beer, wort was prepared at four different barley to wheat malt ratios of 100:0, 25:75, 50:50, and 0:100 (w/w). Additionally, the malts were produced at different germination temperatures and aeration rates (12/32, 18/35, 18/25, 24/18, and 26/25 (°C; L/min)) to consider these two further parameters as well. Thereby, soluble and free phenolic acid contents in wort showed linear correlations to the percentage of wheat in the grain bill, highlighting the absence of synergistic effects when mixing barley and wheat malts. In contrast, the results described the phenolic acid contents as a function of the concentrations in the respective barley and wheat wort, multiplied by their percentage in the grain bill. However, a clear recommendation for favorable barley to wheat malt ratios leading to a decrease of soluble and free cinnamic acid in wort could not be made, as the contents in the present study proved to be highly dependent on the barley and wheat varieties used during mashing and the parameters applied during malting. This was not the case for -coumaric acid for which a clear decrease of the soluble and free forms was found with increasing wheat malt contents. Differently, the soluble form of ferulic acid increased with an increasing percentage of wheat malt, while the free form decreased. The malting parameters clearly recommended high germination temperatures and low aeration rates when aiming at a reduction of undesired cinnamic acid in wort. Fortunately, soluble and free -coumaric and ferulic acid contents were only slightly affected, indicating that the formation of the characteristic wheat beer aroma might not suffer when applying these favorable conditions for styrene reduction.
苯乙烯是小麦啤酒中的食源毒性物质，由于 2002 年国际癌症研究机构将其归类为可能对人类致癌物质，因此必须制定缓解策略。本研究旨在了解糖化过程中大麦与小麦麦芽比例（谷物配方）对可溶性和游离（i）肉桂酸、（ii）-香豆酸和（iii）阿魏酸含量的影响，这些酸是（i）苯乙烯和所需的乙烯基芳烃（ii）4-乙烯基苯酚和（iii）2-甲氧基-4-乙烯基苯酚的前体，在小麦啤酒中，用四种不同的大麦与小麦麦芽比例（100:0、25:75、50:50 和 0:100（w/w））制备了麦芽汁。此外，还在不同的发芽温度和充气率（12/32、18/35、18/25、24/18 和 26/25（°C；L/min））下生产麦芽，以考虑这两个进一步的参数。因此，麦芽汁中可溶性和游离酚酸含量与谷物配方中小麦的百分比呈线性相关，这表明当混合大麦和小麦麦芽时不存在协同效应。相比之下，结果将酚酸含量描述为各自大麦和小麦麦芽汁中浓度的函数，乘以其在谷物配方中的百分比。然而，由于本研究中证明酚酸含量高度依赖于糖化过程中使用的大麦和小麦品种以及麦芽生产过程中应用的参数，因此无法给出有利于降低麦芽汁中可溶性和游离肉桂酸的大麦与小麦麦芽比例的明确建议。对于-香豆酸，情况并非如此，随着小麦麦芽含量的增加，其可溶性和游离形式明显减少。相反，随着小麦麦芽比例的增加，阿魏酸的可溶性形式增加，而游离形式减少。当旨在减少麦芽汁中不期望的肉桂酸时，发芽温度高和充气率低的麦芽生产参数是明确推荐的。幸运的是，可溶性和游离-香豆酸和阿魏酸含量受影响较小，这表明在应用这些有利于降低苯乙烯的有利条件时，不会影响小麦啤酒特征香气的形成。
