Chaozhou's three treasures are old citron, old medicine orange and yellow peel fruit. They are the best in Chaozhou preserves. 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 known as the three treasures of Chaozhou.

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, high quality and original fruit flavor, it was rated as "national new product" and praised by foreign businessmen as the treasure of preserved fruit.

With its unique flavor and many functions, such as promoting digestion, appetizing, reducing fat and weight, eliminating 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 the raw material-cleaning-peeling and pickling-preservation-drying-cleaning-steaming-softening-sugar-stained ingredients-sugar pot processing-glass threshing floor drying-warehousing-packaging. Among them, sugar tank treatment is the key control point. For example, sugar pot treatment before mixing sugar stains 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 products with sugar stains and ingredients at high temperature, but also make the original sugar and ingredients evenly distributed, but the temperature should not be kept at high temperature for a long time, and the high pressure and high temperature should be kept at about 20 minutes, otherwise the beneficial substances of the products will be easily lost.