The three treasures of Chaozhou are old citron, old medicine orange and yellow peel fruit. They are the best among Chaozhou preserved fruit specialties. They occupy an important position in the preserved fruit industry in Chaoshan area, are favored by hipsters and are well-known at home and abroad, so they are called Chaozhou Sanbao.

The production technology of old citron (bergamot) is a traditional food technology in Chaoshan area of Guangdong Province. Because of its mellow or crisp taste, excellent quality and original fruit flavor, it was rated as "national new product" and praised by foreign businessmen as a treasure in preserved fruit.

With its unique flavor and many functions, such as promoting digestion, appetizing, reducing fat and weight, resolving phlegm and relieving cough, it is praised by consumers as "a must in China". In 2009, it was selected into Guangdong Intangible Cultural Heritage List.

Compared with the traditional and ancient processing route, the old citron (bergamot) is raw material-cleaning-peeling and pickling-preservation-drying-cleaning-cooking and softening-sugar stain ingredients-sugar can processing-glass threshing floor drying-warehousing-packaging and delivery. Among them, sugar tank treatment is the key control point. For example, if sugar can treatment is carried out before sugar stains are mixed, it will lead to the disadvantages of low sugar intake, uneven composition, poor taste, low yield and high consumption.

Therefore, sugar pot treatment can not only sterilize the product at high temperature after sugar stains and ingredients, but also make the original sugar and ingredients evenly distributed, but the temperature should not be too high for a long time, and the high pressure and high temperature should be kept at about 20 minutes, otherwise the beneficial substances of the product will be easily lost.