1. Why Is the Inside of Pasta Different After Short and Long Cooking?
Take two pieces of pasta from the same pot of water boiling at about 100°C (212°F). Cook one for a short time and the other for a long time. If you cut them open, the shorter-cooked one is said to have a hard center [2]. Dry pasta cannot be eaten as it is. It must absorb water from the hot water to become soft. However, water does not enter all at once. It moves slowly from the outside toward the center. If the cooking time is short, the water does not reach the middle.
The secret to softness is starch in the wheat flour. When starch grains absorb water and swell, this change is called gelatinization [8]. Gelatinization happens first on the outside of the pasta and last in the center. This is not just imagination; it has been measured. The National Agriculture and Food Research Organization (NARO) used MRI to look inside dry spaghetti. They reported that cooked noodles have a part in the center where gelatinization is incomplete and moisture is low [2]. So, how does this "hard center" affect eating?
2. What Does "Al Dente" Mean for Pasta Cooked with a Hard Center?
In Italian cooking, cooking pasta so that a slight hardness remains in the center is called "al dente." The heat has reached it, but there is still a bite to it. A Japanese study looked at this difference. Researchers compared spaghetti cooked for different times. They reported that the longest-cooked sample was soft because the ungelatinized part in the center had disappeared [1].
On the other hand, the shortest-cooked sample changed its properties greatly when mixed with sauce. It seems less of the sauce components entered the center. The study states that whether there is an ungelatinized part in the center is one factor affecting ease of eating [1]. So, cooking time affects not just hardness, but how well it goes with sauce. Deciding when to take the pasta out of the pot is a choice about stopping when water and heat have reached a certain point inside the noodle.
This was the story about "time." Now for another mystery: does the salt in the water affect this change in the center?
3. Does Adding Salt Make Boiling Water Hot Enough to Cook Pasta Faster?
Some people think adding salt makes the water hotter, so pasta cooks faster. It is true that dissolving salt raises the boiling point slightly. But how much? Let us calculate. If you dissolve 10g of salt in 1L of water (1%), the amount of salt is about 0.17 mol (calculated as 10 divided by 58.44). Salt splits into two parts when dissolved, so there are about 0.34 mol of particles. Multiplying this by the boiling point elevation constant for water (0.52°C·kg/mol) gives about 0.18°C (0.32°F). This is an approximation for an ideal solution, so real values may differ slightly.
Cooking guides also say that even if the temperature rises by about 0.5°C (0.9°F), it does not affect the pasta [3]. Since there is a difference between the calculated 0.2°C and the mentioned 0.5°C, we can consider the rise to be "less than 1°C." Therefore, boiling water with household amounts of salt stays at about 100°C (212°F). The rise in boiling point is small [3]. So, why do we add salt?
4. Does Salt in Pasta Water Only Add Flavor, or Does It Change Texture?
The reason most often given for adding salt is to season the pasta. A guideline is 5–10g of salt per 1L of water (0.5–1%), with 1L of water for 100g of pasta per person. However, this is a guideline from cooking experts, not an official standard. Views on its effect on "firmness" differ among commentators [7].
There is research suggesting salt affects texture and structure, not just taste. A study published in *Physics of Fluids* in 2022 reported that the hardness (elastic modulus) of cooked pasta was very sensitive to the amount of salt in the water [5]. However, this study did not explain how salt concentration affects cooking time.
A study published in *Food Hydrocolloids* in 2025 used X-ray and neutron scattering. It suggests that in regular spaghetti, wheat gluten acts like a "safety net" protecting starch grains, making it relatively strong against overcooking or too much salt [6]. Salt is said to help maintain structure only at the right concentration and time. The study also compares pasta without gluten.
Note that a study on boiling spinach found that higher salt made it softer, with good texture at 0.25–0.5% but too soft at 2% [4]. Since vegetables and noodles are different things, this result cannot be directly applied to pasta. Research shows salt may affect texture and structure beyond taste, but many questions remain.
5. How Can You Compare the Center of Pasta by Changing Cooking Time?
You can check the changes inside yourself by varying the cooking time. Use a guideline from the pasta package. Cook three pieces of pasta in the same pot. Take one out after about half the listed time, one at the listed time, and one slightly longer. Let them cool, then cut them. Compare the color and hardness of the center and the bite when chewing. Check with your eyes and teeth if the inside is different even though the water temperature was the same.
If you want to read more, NARO's report on food research is available in Japanese [2]. It shows diagrams of moisture distribution inside spaghetti for each cooking time. Start there to follow how the center changes.