Department of Viticulture and Enology, University of California Davis, One Shields Ave., Davis, CA 95616-5270, USA.
The Australian Wine Research Institute, PO Box 197, Glen Osmond, SA 5064, Australia.
Food Chem. 2019 Nov 1;297:124923. doi: 10.1016/j.foodchem.2019.05.197. Epub 2019 May 30.
Red wines injected with nitrogen or oxygen during fermentation were used to identify the effect of gas exposure on tannin structure and reactivity with poly-l-proline. Tannin was purified from wine after fermentation and after three years of bottle storage. Tannin from nitrogen-treated wine had a lower percentage of galloylation and were less pigmented than tannin from oxygen-exposed wine. Self-aggregation of tannin was measured by nanoparticle tracking analysis and a larger particle size was observed for the oxidized treatment. The interaction of tannin and poly-l-proline was measured by isothermal titration calorimetry, and involved more hydrogen bonding than hydrophobic interactions in the case of nitrogen-treated wine tannin. Conversely, oxidized tannin was more hydrophobic and the association with poly-l-proline was entropy-driven due to a change of solvation. The results show meaningful changes in the structure and reactivity of tannin as a result of oxygen exposure during fermentation, which may impact astringency perception.
红葡萄酒在发酵过程中注入氮气或氧气，以研究气体暴露对单宁结构和与聚-l-脯氨酸反应性的影响。单宁在发酵后和经过三年瓶储后从葡萄酒中纯化出来。与暴露于氧气的葡萄酒相比，经氮气处理的葡萄酒中的单宁酯化程度较低，颜色较浅。通过纳米颗粒跟踪分析测量单宁的自聚集，观察到氧化处理的颗粒尺寸更大。通过等温滴定量热法测量单宁与聚-l-脯氨酸的相互作用，结果表明，氮气处理的葡萄酒单宁中的氢键相互作用比疏水相互作用更多。相反，氧化的单宁疏水性更强，与聚-l-脯氨酸的缔合是熵驱动的，这是由于溶剂化的变化。研究结果表明，发酵过程中氧气暴露会导致单宁结构和反应性发生有意义的变化，这可能会影响涩感。
