If we look in any traditional Western cookbook at the section on stews, rice dishes and soups, we will see that most recipes begin with an invariable litany: that of the preparation of a humble base of fried or sweated vegetables, known in Spanish as the 'sofrito'. The composition varies from country to country, but is essential in kitchens in Spain, Italy, France, Portugal, etc. In America it is found in all the Creole recipes, from Cajun cuisine, which came with the French, to Latin recipes (Brazil, Antilles and Caribbean, Colombia, Ecuador, Argentina ...).
Although umami was not defined until 1909 by the Japanese chemist Kikunae Ikeda, the ability of glutamate and other amino acids, present in many foods, to enhance and harmonise the flavours of other ingredients has been used since ancient times. In classical Rome, the base was usually garum, a fermented fish sauce which evolved into soya and fish sauce in oriental cooking. These cultures use short cooking periods (in a wok sautéed or lightly boiled), and these sauces provide body and highlight the rest of the ingredients.
The use of garum was discontinued after the fall of the Roman Empire, and the next great civilisation that influenced much of Mediterranean cuisine, the Arabs, resorted to spices instead of umami to enhance of flavours.
However, sofrito is mentioned in the 'Llibre de Sent Soví', an anonymous recipe book of Valencian cuisine dating from 1324. Light frying ('sofreir' is frying at temperatures between 120 and 150º C, lower than those of quick cooking in oil), originally used onions or leeks and fatty bacon. This method, ignored in the great recipes of the Golden Age, appears again in the humble recipe book by the Aragonese friar Juan de Altamiras, 'New art of cooking, taken from the school of economic experience', written in 1758, and incorporates a fundamental ingredient found today in Spanish sautéing: the tomato.
America contributed the tomato to the sofrito and the technique was taken overseas by the Spanish colonists. Curiously, the country from which the tomato originated, Mexico, did not use sofrito in its traditional cuisine.
What is the magic of sofrito in rice dishes, casseroles, soups and numerous stews? The key is in the Maillard reaction that is triggered in vegetables subjected to temperatures above 100º C. As Ali Bouzari sums up in his book 'Ingredients', the small proportion of proteins contained in vegetables in this process become "the wick that turns on the sugar pump". Thus, complex flavours are developed: sweet, toasted and umami, especially with tomatoes, which contain up to 0.3% of glutamic acid.
However, do not make the mistake of discarding the seeds, because they are where the glutamic acid is concentrated in greater quantities. Chemistry also explains why you have to follow a traditional order of frying the other ingredients first and leaving the tomato for last: once the tomato is added, its acids harden the rest of the vegetables and make cooking difficult.
British gastronomic writer Mina Holland in her book 'The Edible Atlas' states that the composition of sofrito is a signature of the kitchens that use it. So, while the Spanish use garlic, onion, pepper and tomato, France uses shallot and leek, celery and carrot; Italy, onion, carrot and celery; Portugal, only garlic and onion; American Creole cuisine, pepper, celery and onion, etc. So dedicate some time to making sofrito, you can always make large quantities and freeze it in portions, ready to make countless dishes.