What change occurs during the pre-cook of fries?

During the pre-cook of fries, one of the key transformations is that they change color slightly. This process involves par-cooking the potatoes, which helps to remove some moisture and kickstarts the cooking process. The color change indicates that the starches are beginning to gelatinize, which contributes to their texture and flavor when they're finished cooking.

The other choices do not accurately describe the initial phase of fry preparation. For instance, fries do not become crispy during this stage; that crispiness develops during the final cook, where they are cooked at higher temperatures. Similarly, although they do soften somewhat during the pre-cook, the noticeable aspect is the slight color change. They don't significantly increase in size during this phase either, as the size increase generally happens when they are fully cooked and moisture is lost, creating that characteristic fluffy interior.