求翻译：将葡萄推迟采收，当气温低于-7℃以下，使葡萄在树枝上保持一定时间，结冰，然后采收、压榨，用此葡萄汁酿成的酒。是什么意思？

To defer grape harvest, when the temperature falls below-7 ° c, make the grapes remain some time in the branches, icing, and then harvesting, pressing and juice made from this grape wine.