We often hear that common to add sugar, sucrose, to a food with strong sour feelings will lessen the same. What is the acidity of a food? Of course the answer is obvious: is defined as the presence of high concentration of acids in its composition. It is an intrinsic characteristic of the food itself.
The free acidity, ie the presence of these acids as is "without any link with other molecules, is present in almost all foods. It is the concentration, then the quantity, quality and acid itself, out the power of perception. For example, the tomato has a good concentration of citric acid and malic acid. These acids, whether in free form and in high numbers, contributing to the sour taste the vegetable. Usually, as a practice of cooking, add sugar to lower that common feeling during cooking. According to this custom is generally believed that sugar lowers the acidity of the sauce and then change the pH of the same. We could do other instances like sweetened lemonade or sweet and sour mixture of vinegar and sugar. Even knowing the pH of the solutions do not undergo any alteration in the presence of sugar, we wanted to check with a laboratory test the behavior of the pH of a solution acetic acid and sucrose, reproducing the steps that take place in the kitchen.
we poured 10 ml of red wine vinegar in a flask and its pH measured with an electronic pH meter, setting the value of 3.10 at room temperature about 20 ° C.
Weigh a quantity of sucrose (common sugar) is equal to 1.12 g and add the vinegar. Sugar dissolved, check pH recording the same value, 3.11 at 20 ° C approx.
From this first test, the pH of the solution has not undergone major changes remaining unchanged.
Increase the amount of sucrose 5 g in the same amount of vinegar, adjusting the pH. We bring the solution to a temperature of 50 ° C to simulate the early stages of cooking. Expect that the temperature is restored to the initial course of 20 ° C, because we know that high temperature (heat) affects K to the solution (K = to acid dissociation constant), staggering slightly from the value 3.11 is increased up to a pH of 3:49, we waited for the solution to return to room temperature by detecting the pH value of 3.11.
Increase the amount of sugar a 10 g per 10 ml di aceto e, procedendo come prima, rileviamo il valore del pH invariato di 3,10.
Possiamo affermare che lo zucchero, a qualsiasi concentrazione, non altera il pH di una soluzione acida.
La percezione dell'acidità in presenza di zucchero, per un processo fisiologico ancora sconosciuto, è inferiore. La limonata zuccherata, o l'agrodolce, pertanto, risultano meno acidi non per trasformazioni chimiche ma per esclusive caratteristiche percettive.
Il nostro cervello elabora i segnali trasmessi dalle papille gustative in tali termini. 
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