Tomato puree is the heart of many Italian recipes, yet a pinch of extra acidity is enough to put even the most passionate cook into crisis. The taste of tomato and puree is a delicate balance between sugars and acids present within it: the natural presence of acids, such as malic and citric acid, and the state of ripeness can in fact influence the final flavour. Furthermore, other compounds can form during cooking, such as pyroglutamic acid (PCA), which can increase the acidity of the puree and give an unpleasant taste. There are two main home methods to correct acidity. Sodium bicarbonate (NaHCO3) reacts with acids through neutralization, forming carbonic acid which then decomposes into water and carbon dioxide, reducing Really the acidity. Sugar, on the other hand, does not react directly with acids but masks the flavor: sucrose balances the presence of acids and binds to the receptors of the taste buds, compensating for the acidic sensation. Both methods make the pass more balanced, but through different mechanisms.
Tomato puree: between sugars and acids
Tomato puree is a typical food of Italian cuisine, obtained from the processing of fresh tomatoes. Traditionally it is prepared by cooking ripe tomatoes, removing the skin and seeds and then pureeing them – that is, sieving them – until a smooth, dense and homogeneous sauce is obtained. Tomatoes are fruits that contain high levels of sugars and organic acids. Among the main sugars we find fructose and glucose, while for acids we have malic acid and citric acid, with the latter tending to decrease its quantity as maturation progresses, while the quantity of malic acid tends to remain almost unchanged. The balance between these two classes of substances influences the final flavor of the puree, and strongly depends on the stage of development and ripeness of the tomatoes used.
Furthermore, an overall increase in the amount of organic acids can occur during the heat treatment of tomatoes. For example, the degradation of glutamine (an amino acid) leads to the formation of an acid called pyroglutamic acid (PCA), which can affect the final flavor of tomato puree, also giving it a sour and unpleasant taste.
How sugar works to cover the acidity of the sauce
One of the best known remedies for too acidic tomato puree is to add sugar. The classic table sugar is nothing more than sucrose, a disaccharide made up of the union of two simple carbohydrates, glucose and fructose. When it comes into contact with our tongue, sucrose binds to its specific receptors present in the taste buds, making us perceive a sweet taste and reducing acidity. Therefore sucrose and acids do not “cancel” each other, but compensate sensorially, creating a more harmonious and pleasant balance, leaving the concentration of the acids present in the puree unchanged.
How to use baking soda to neutralize acidity
Another technique involves adding a little bit of baking soda to neutralize the acids naturally present in the tomato. From a chemical point of view, it is a reaction between two classes of substances: acids and bases. Acids, including those naturally present in tomatoes, tend to release protons into solution (H ions+), while bases, such as sodium bicarbonate, tend to capture these released protons. When we add bicarbonate to tomato puree, we are causing a base to react with all the acids present in the food: acids and bases establish a specific reaction between them known as the neutralization reaction. In this process, the H+ Some acids react with bicarbonate to form carbonic acid (H2CO3), which then decomposes into water and carbon dioxide.
The acids are thus transformed into neutral substances (this is why we speak of “neutralization”) and the total amount of acidity present in the puree decreases.
