The research team determined that the extra sweetness likely came from grape syrup, added to the champagne before corking.
研究小组确定额外的糖分很可能是瓶塞封住前加入的葡萄糖浆。
英语百科
Grape syrup
Grape syrup is a food produced (mostly in the past) in the United States, in ancient Rome, in Iranian cuisine, and in Greek cuisine. Along with other fruit syrups, it is sometimes used to top pancakes or waffles. It can be made from concentrated grape juice and one preparation is to boil grape juice.