National Research Institute of Brewing, 3-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima, 739-0046, Japan.
Faculty of Food and Agricultural Sciences, Fukushima University, 1 Kanayagawa, Fukushima, Fukushima, 960-1296, Japan.
Sci Rep. 2019 Jul 30;9(1):11039. doi: 10.1038/s41598-019-47331-0.
The stable isotopic composition of oxygen (δO) in wine is often analysed to determine the geographic origin of the wine and the amount of water dilution. However, little is known regarding the effects of two major winemaking techniques (the addition of acid (acidification) and sugar (chaptalization)) on the δO value of water in wine. Here we show that acidification and chaptalization have minor direct effects on the δO value but indirect effects based on the ethanol yield, which causes isotopic variation of up to 0.6‰. During fermentation, δO values increase at low ethanol yields, suggesting that yeast release water with a high δO value into wine when consuming sugars. Additionally, the ethanol yield is negatively correlated with the consumption of amino acids by the yeast, indicating that yeast growth decreases the ethanol yield. We therefore identify ethanol yield, which is decreased by the consumption of sugars by yeast for non-alcohol-fermentation processes as a potential factor leading to variations in the δO value of water during the winemaking process.
葡萄酒中氧的稳定同位素组成（δO）通常用于分析葡萄酒的地理起源和水稀释的程度。然而，对于两种主要的酿酒技术（添加酸（酸化）和糖（加糖））对葡萄酒中水的δO 值的影响知之甚少。在这里，我们表明酸化和加糖对δO 值的直接影响较小，但基于乙醇产量的间接影响较大，这会导致同位素变化高达 0.6‰。在发酵过程中，当酵母消耗糖时，乙醇产量较低，δO 值会增加，这表明酵母会将高 δO 值的水释放到葡萄酒中。此外，乙醇产量与酵母消耗氨基酸呈负相关，这表明酵母生长会降低乙醇产量。因此，我们确定了乙醇产量，即酵母消耗糖进行非酒精发酵过程会降低乙醇产量，这可能是导致酿酒过程中水中δO 值变化的潜在因素。
