Xuanwei ham, also known as Yuntui, is one of the three famous legs in China, and it is the second local specialty in Zhejiang that has been listed as "origin protection" after Shaoxing yellow rice wine [1]. Xuanwei ham is made of fresh pig hind legs from Wujin pig producing area, which are trimmed and shaped, pickled, laminated, washed and shaped, hung, air-dried and fermented. It is famous for its excellent color, fragrance, taste and shape, and has been widely praised by Chinese and foreign consumers. However, there are some white spots in some ham muscles, which affect the sensory quality of ham to some extent, and even some consumers worry that these white spots are parasites or microbial colonies [2], which significantly reduces the commodity value of products, has a direct adverse impact on product sales and harms the interests of enterprises. Studies at home and abroad show that white spots in dry-cured ham muscle are composed of degradation products of protein, mainly tyrosine [3-4]. Different scholars have different views on the formation mechanism of ham muscle white spot. Butz et al. [5] think that white spots are caused by tyrosine precipitation; Cantoni et al. [3] found that myofibrillar protein with less sarcoplasmic protein and tyrosine has a great relationship with the formation of white spots; Toldra et al. [6] found that the formation of white spots is due to the deposition of protein. The free amino acid content of these protein precipitates is 250μg/mg, in which 1 17μg/mg is tyrosine.