until后面直接加形容词

请问老师们，这句话的until后面为何可以直接加形容词呢，是省略了什么嘛？

The potato cakes can be shallow or deep-fried until crisp outside andmeltingly soft inside.

薯饼可以微煎或熟炸，直到变得外脆内软。

还有这个短语 cook the patties until crisp and freckled on bothsides

The potato cakescan be shallow or deep-fried until crisp outside and meltingly soft inside.

薯饼可以微煎或熟炸，直到变得外脆内软。

——这是时间从句省略了主语和 be 动词。等于：

The potato cakescan be shallow or deep-fried until （they are）crisp outside and meltingly soft inside.

还有这个短语 cook the patties until crisp andfreckled on both sides

——同理。 Cook the patties until （they are）crisp andfreckled on both sides.