Why boiled potatoes go mushy.
Different varieties of potatoes are suitable for different uses. Some are grown for baking, other varieties for boiling etc.. A baking potato will not be a very good boiling potato, and vice-versa.
But, sometimes a ‘boiling’ potato gives poor results, collapsing or ’sloughing’ in the pan, to produce a mush. This is because growing conditions (particularly the nutrition and irrigation) have a greater effect on the cook-ability than variety. Where, when and how the potatoes were grown accounts for about two-thirds of the variation in cooking qualities, with variety only causing one-third of the variation.
The low solids potatoes, the guaranteed stay-whole boilers, probably need more irrigation and higher N applications. Soil should be well fertilised or have a good dressing of farmyard manure before potatoes are sown.
The texture of a cooked potato is directly related to dry matter content. Potatoes are described as moist to wet if they have a low dry matter content, or mealy when dry matter is high. Potatoes, such as Norland, with a low dry matter hold together well when boiled, but tend to be wet when baked. Potatoes such as Russet Burbank, which have a high dry matter content, may slough or break up when boiled, but have a dry, mealy texture when baked.
Research into the culinary quality of potatoes indicates that sloughing and mealiness of steamed potatoes increases with tuber Specific Gravity. This relationship means that the likelihood of steamed tubers having particular textural characteristics can be predicted from their Specific Gravity.
Do-it-yourself Specific Gravity Test for Potatoes
Add 225gm table salt to 1775 gm water and stir until dissolved. The temperature should be around 20C. This produces a salt solution with a specific gravity of about 1.080.
Place the potatoes into the solution, one at a time. If they float, they will be good, firm boilers. If they sink, they will probably be mealy when boiled. These are high dry matter potatoes, and probably best steamed.
The culinary quality of potatoes can be influenced by crop management, particularly irrigation and nutrition.
