坊间一直认为,血燕是金丝燕咳血的产物,营养价值比普通燕窝高。其实,血燕所呈现的颜色是燕窝中所含的矿物质因长期氧化而变色。变色的原因主要有以下三个方面:1.金丝燕以海边藻类、深山昆虫飞蚁等为食,这些食物中富集了大量的矿物质,因此其唾液中也含有较多的矿物质;2.金丝燕筑巢的岩壁中含有的矿物质会通过燕巢与岩壁的接触面 Square has always believed that blood swallows are the product of the Swiftlet hemoptysis, nutritional value higher than ordinary bird’s nest. In fact, the color presented by Xue Yan is the mineral contained in the bird’s nest discolored by long-term oxidation. The causes of discoloration are as follows: 1. Swiftlet feeds on seaside algae, mountain insects, ants and other insects. These foods are rich in minerals and therefore contain more minerals in their saliva. 2. Swiftlet nests contain minerals that pass through the nest’s interface with the rock wall