Bravi Elisabetta, Perretti Giuseppe, Buzzini Pietro, Della Sera Rolando, Fantozzi Paolo
Department of Economic and Food Sciences, Section of Food Technology and Biotechnology, University of Perugia, 06126 Perugia, Italy.
J Agric Food Chem. 2009 Jul 22;57(14):6279-84. doi: 10.1021/jf9007423.
Knowledge of lipid content and composition in the brewing process enables the quality control of the final product. Lipids have a beneficial effect on yeast growth during fermentation as well as deleterious effects on end-product quality. The lipid content of a beer affects its ability to form a stable head of foam and plays an important role in beer staling. Lipid oxidation during wort production is of great interest because of its effect on beer quality: both lipids and their oxidation products are known to have adverse effects on beer flavor, whereas interactions between lipids and protein films stabilizing the gas bubbles are thought to cause the collapse of foam. In this background, the aim of this research was the characterization of the lipid content during a brewing process for evaluating the influence of both technological steps and yeast biomass in the lipid composition of beer. Lipid contents and their fatty acid profile were evaluated in brewing raw materials, wort, and beer. A high-resolution gas chromatography-flame ionization detector (HRGC-FID) system was used for fatty acid determination in lipid extracts. The results of the present study highlighted that the main technological steps influencing the lipid content in brewing byproduct and beer were clarification in a whirlpool and filtration. Moreover, the presence of metabolically active yeast cells (used as starter culture) were found to have a great influence on the fatty acids composition of lipids.
了解酿造过程中的脂质含量和组成有助于对最终产品进行质量控制。脂质在发酵过程中对酵母生长有有益影响，但对最终产品质量也有有害影响。啤酒中的脂质含量会影响其形成稳定泡沫头的能力，并且在啤酒陈化过程中起着重要作用。由于麦芽汁生产过程中的脂质氧化对啤酒质量有影响，因此备受关注：已知脂质及其氧化产物都会对啤酒风味产生不利影响，而脂质与稳定气泡的蛋白质膜之间的相互作用被认为会导致泡沫破裂。在此背景下，本研究的目的是表征酿造过程中的脂质含量，以评估工艺步骤和酵母生物量对啤酒脂质组成的影响。对酿造原料、麦芽汁和啤酒中的脂质含量及其脂肪酸谱进行了评估。采用高分辨率气相色谱 - 火焰离子化检测器（HRGC - FID）系统测定脂质提取物中的脂肪酸。本研究结果表明，影响酿造副产物和啤酒中脂质含量的主要工艺步骤是在回旋沉淀槽中的澄清和过滤。此外，发现代谢活跃的酵母细胞（用作起始培养物）的存在对脂质的脂肪酸组成有很大影响。
