someone says that temperature is the most reliable way to know if a food is done is or not
they say that there are various signals to know but none of these are actually that reliable
(source: How can I ensure that scrambled eggs will be fully cooked?)
they do not mention the most reliable way, they only mentioned time. the 'suggested time' given on recipes, as we know, is also not very reliable because few recipes are well-tested by the person that made that recipe, but many (a very large percentage) are not tested and or based on significant evidence
(source: How can I tell if the food inside a pressure cooker is done cooking?)
Best Answer
Unfortunately, temperature is not a good way to determine when pasta is cooked. It's great for some things that are simply done when they reach a given temperature, without time being a factor. Meat is the most common example, but it will certainly work for eggs too as noted on the question you linked.
Pasta is different - cooking involves hydrating it, not just heating it. If you're cooking it in boiling water, it will most likely all reach 100C/212F before it's done, and then still be at that same temperature when it's done. On top of that, it'd be very difficult to actually stick a thermometer into pasta to get a reliable temperature reading, and it's so small that it'd be cooling down rapidly once you take it out of the water to do that.
The most reliable way to tell if your pasta is done is to simply test it directly - bite through it and see what the texture is, or I suppose cut it with a knife if you don't want to bite possibly underdone pasta for whatever reason. If it's not done yet, you'll see an opaque, whiter bit in the middle. For far more detail, see What's the best way to tell that pasta is done (when boiling)?
The times given on packages are also fairly accurate, though there's some room for personal preference in doneness.If you cook it as instructed, it will definitely be done - but it might be either softer or more "al dente" than you prefer, depending on the brand and your preferences. (Some packages may actually give an "al dente" time and a "fully cooked" time, if you're really lucky.)
If you're looking for consistency, and not having to test every time, you can just time it once. That time will keep on working for you, if you cook it the same way. As a bonus, you can also compare that time to what's on the package. If it matches, you can probably use the time on the package for all types of pasta from that brand, and if you like it cooked 10% less, you can extrapolate a very good guess for other types, and so on.