I am a chef, and I often encounter the same problem in restaurants. My personal suggestion is that you'd better add more soup when cooking braised pork. When stored in the refrigerator, because the meat will be covered with soup and condensed oil, it is not easy to come into contact with the air. In addition, when heated, braised pork is colored with sugar, and the colored meat will be rolled down by the boiled soup, which looks very dull.

dull

Black, you'd better add some water when heating.

When cooked for a while, the meat will thicken with the heating of the soup.

Slowly recolor.

The above personal experience, I hope to answer your questions.