Microwaved pasta tends to become mushy and soft because of the way microwaves heat food. Unlike cooking on a stove top or in an oven, where the heat is transferred through direct contact with a hot surface or through hot air circulation, microwaves work by emitting electromagnetic waves that excite water molecules in the food, generating heat from within.
When pasta is cooked on a stove top or in an oven, the heat is evenly distributed throughout the cooking vessel, allowing the pasta to cook more uniformly. This leads to the desired result of al dente pasta, which has a firm texture. On the other hand, when pasta is microwaved, the heat is primarily absorbed by the water molecules within the food, including the moisture present in the pasta itself.
As the water molecules become heated, they turn into steam, creating a moist environment around the pasta. The steam contributes to the softening and moistening of the pasta, which can result in a mushy texture. Additionally, the lack of direct heat and the relatively short cooking time in a microwave can contribute to uneven cooking, further affecting the texture of the pasta.
To achieve a crispy and crunchy texture with pasta, methods that involve direct heat or exposure to dry heat, such as cooking in a pan or baking in an oven, are more effective than using a microwave. These methods promote evaporation of moisture from the pasta, leading to a drier and firmer texture.