Choosing the Right Potatoes for Gnocchi
The first step when making potato gnocchi is choosing the right potatoes. There are many different types and varieties and not all potatoes make great gnocchi. You also want to choose potatoes that are all of the same size so that they cook uniformly.
Different Types of Potatoes
When buying potatoes, this is what you don't want to buy: potatoes with damaged skin, greenish potatoes (when they turn green, they can be toxic), potatoes that have a black tinge or mold.
Potatoes come in different colors with a yellow, red, or purple outer skin or with white, yellow, red, or even blue flesh. However, the most important quality for culinary purposes is its density, in other words, the amount of total solids (starch, sugar, fiber, protein, salt) compared to the amount of water. Some qualities are best for certain dishes and not great for others.
Mealy or starchy potatoes are high density potatoes and have high levels of starch. These potatoes are great to make baked potatoes or potato puree (and, therefore, gnocchi!). When they are cooked, they become soft. When they are boiled, they tend to fall apart. Mealy varietals are usually large (like Russet or Idaho potatoes).
Waxy potatoes are low density potatoes and they have low levels of starch. When boiled, these potatoes don't fall apart and remain somewhat hard in texture. Waxy varietals tend to be small (like Yukon Gold potatoes).
There are also potatoes that are somewhere between mealy and waxy, with medium levels of starch and medium density. They can be used in many different recipes but this all-purpose quality makes them actually not great for any dish.
The Best Types of Potatoes for Gnocchi
To make gnocchi, our grandmothers and mothers prefer mealy potatoes, rich in starch, and slightly aged as they lose more of their water content over time. Old potatoes does not mean germinating potatoes, but drier potatoes which provide a dry and compact dough.
Stay away from waxy potatoes that have a hard pulp. And avoid new potatoes due to their high amount of water content.
The perfect gnocchi are made with starchy and aged potatoes and here's why. The higher the water content of your potato, the more flour you will have to add when making potato gnocchi. Adding excess flour will make your gnocchi hard and rubbery and you that's not what you want.
How to Store Potatoes
Once you find the perfect quality for gnocchi, make sure you store the potatoes properly. Potatoes have a very low cellular respiration, so they can last up to months on end! Place them in a dry and dark place at room temperature.
Potatoes must stay away from sunlight as it triggers the production of a toxic substance called solanine. Do not store potatoes in the refrigerator as some of their starch will turn to sugar causing your potatoes to turn brown when cooked at high temperatures.