Birds’ Nest Colors
Swiftlet’s nests exist in three different colours: white, yellow (gold), or red (sometimes called “blood” nest). The colour of the edible birds’ nest (EBN) showed major differences following the place they are harvested, either from caves or houses. In caves, the two projections by which the nest’s cup is attached to the cave wall are usually stained with blood colour in fresh EBN but darken to brown with time, upon harvesting.
Some people believed that the EBN become red due to the saliva of the swiftlets building their nest were laced with blood, whereas some believed the swiftlets consumed lotus seeds, seaweeds or molluscs where the reddish hue mixes with the bird’s saliva. Studies were done on the red EBN, where it turns out that the red colour was due to the oxidation of nitrate in swiftlets’ droppings. The redness of EBN is strongly related to nitrate and nitrite, where the cave EBN has a higher content of the minerals, which gives the cave EBN, a slightly yellowish to reddish or darker coloured compared to the house EBN. The sodium nitrite within the EBN might cause the formation of aryl-C-N and NO2 side groups in aromatic amino acids of white EBN, which makes the white EBN transformed into red colour. House EBN usually appears whitish due to lower nitrate and nitrite contents.
Golden and Red types are rarer as they can be harvested only from certain caves in South East Asia and many connoisseurs believe that these types of nests have richer mineral content and higher quality, and therefore command a premium price.
