If you add butter to pasta sauce, the butter makes the pasta sauce richer and smoother as well as glossier.
The butter added to the pasta sauce, makes the pasta sauce richer, smoother and glossier by emulsifying the liquids and fats, while also mellowing the acidity for a more balanced and luxurious flavor and silky texture which clings better to the pasta.
The butter in the pasta sauce also transforms the lower fat sauces like the tomato based sauces, by adding body and preventing them from becoming starchy or pasty.
The key affects of adding butter to pasta sauce are emulsification, gloss and sheen, acidity reduction, texture and creaminess and richness and flavor.
The butter binds the sauce and starchy pasta water together and helps the sauce cling to the pasta perfectly.
The butter in the pasta sauce also gives the finished pasta dish a beautiful and appealing gloss.
The fat in the butter, helps to soften the sharp and abrasive taste from the tomatoes or onions and rounds out the sauce.
Butter added to pasta sauce also creates a velvety, smooth consistency, which makes the pasta sauce feel more decadent as well.
And the butter in the pasta sauce adds a rich and delicate flavor and also enhances other tastes in the pasta sauce.
To add butter to your pasta sauce, cook the pasta until al dente and reserve a cup or two of starchy pasta water.
Then add the drained pasta directly to the sauce in it's pot and turn off the heat and stir in cold butter and a splash of pasta water.
Next toss the pasta in the buttered pasta sauce until the butter melts and emulsifies, which creates a cohesive glossy sauce that coats the noodles.