The reason and prevention of four kinds defects including surface wrinkled skin (carbon built-up), chock, blow hole, deformation, was introduced in this part of the article.
本部分主要介绍表面皱皮（积碳）、呛火、气孔、尺寸超差及变形等缺陷的产生原因和防止方法。
3
As Americans were encouraged to cut sugar intake and eat more fiber and antioxidants, the sweet potato - chock full of vitamins - began to show up on plates again.