• 作者： 秦道堅
• 作者服務機構： 中國文化學院
• 中文摘要： Pidans serve as a kind of Chinese favo-rite food, which is often sold in the markets.Traditionally, they are made by coating duckeggs with a mixture of wood ash, lime andclay etc. for one month. The author has thoroughly studied theformation of pidans on view of chemical as-pect more than thirty years. A new methodhas discovered for making pidans by immer-sing duck eggs as well as hen eggs in a solu-tion of sodium hydroxide (8-9%) and com-mon salt for four days· The product is asgood as traditional ones, and the egg-whiteis coagulated with yellowish, transparent andelastic characteristics. The taste is the samewonderful. However, the time of ripening ismuch shorter. The process is convienent andcheap. The product is clean and handy，with-out the dirty coating of earthern ash. The composition of pidans is chiefly con-sisted of denatured proteins, which is·for-med by the action of alkali upon proteins. Itis a kind of alkali-albuminate, which gives aspecial alkaline taste. Of course, other reac-tions are also included during the formation.For instances, primary and partial hydrolysisof albumin, deamination, decarboxylation，andsalts formation of proteins would also occur. From the chemical composition of pidans,it reveals that the percentage of oil and fatin the yolk is somewhat decreased, but theincrease of mineral salts and carbohydratecontents would balance the loss as comparedwith the fresh eggs. And the food value isalmost the same as the originals. The apparent difference between pidansand fresh eggs is that the former impartsspecial taste. It is taken raw. It can bepreserved for a longer time, and won't spoileven storing over one year. This is, too, anexcellent means for the preservation of eggsdevised by the ancient Chinese hundreds ofyears ago.
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