What's the difference between yellow and black when buying preserved eggs? Which is better?

From the production technology, the difference between yellow preserved eggs and black preserved eggs lies in the content of edible soda ash and external lime. The former has a lower content and the latter has a higher content, so there are two results when making. A yellow heart or a red heart and a black heart, but there is no problem with both, so you can safely eat them. At the same time, yellow preserved eggs are mostly made of eggs, with few egg whites and yolk components and short storage time, which is called "preserved eggs". Black preserved eggs are mostly made of duck eggs. Egg whites and egg yolks have heavy components and long storage time. Adding pine branches and cypress branches to the ingredients is called "preserved egg".