Slicing a vegetable on the bias increases its surface area compared to slicing it straight across. This increased surface area allows for faster and more even cooking.
When you slice a vegetable straight across (perpendicular to its length), you create a circular or oval cross-section. The surface area of this slice is relatively small. However, when you slice on the bias (at an angle), you create an elongated, oval-shaped slice. This elongated shape inherently has a larger surface area than the straight-cut slice. The more acute the angle of the bias cut, the longer and wider the slice becomes, further increasing the surface area. This increased surface area is beneficial in cooking because it allows more of the vegetable to come into contact with heat, oil, or sauce, leading to faster and more even cooking. It also enhances the absorption of flavors.
When stir-frying vegetables, slicing them on the bias not only increases surface area for faster cooking but also creates visually appealing pieces that are more uniform in size, leading to a more consistent cooking result.