## 1 Introduction  
Balsamic vinegar produced in Modena and Reggio Emilia, Italy, is one of the most widely known vinegars on the European continent. The name \"balsamic\" comes from the word balm (medicinal ointment) because its miraculous medicinal abilities were assumed, for example, in the fight against the plague. The first mention of this vinegar dates to the 11 th century, when it was given to the Emperor of the Holy Roman Empire, [PERSON]. In the following centuries, it was a gift to other important personalities [1]. At the end of the 16 th century, the [PERSON] of Este used this vinegar as a gift for the nobles. The Napoleonic Wars, during which Duke [PERSON]'s supplies were stolen, may have been responsible for spreading balsamic vinegar into the world. Another act, spreading balsamic vinegar throughout the world, occurred in 1862, when an Italian lawyer, [PERSON], revealed in a letter the secret of making balsamic vinegar to his friend, from whom the recipe spread next [2]. To preserve its tradition and origin, balsamic vinegar received a protected designation of origin in the year 2000, which allows products called \"traditional balsamic vinegar of Modena\" (TBVM) or \"traditional balsamic vinegar of Reggio Emilia\" (TBVRE) and \"balsamic vinegar from Modena\" (BVM) to be produced only in these two Italian provinces [3]. Vinegars, known as \"balsamic vinegars\" (BV), do not bear any protected designation of origin and can be produced anywhere in the world [4]. The TBVM and TBVRE production process (Figure 1) is completely unique and includes the concentration of grape must (the most used varieties are Trebbiano Modenese, and Lambrusco) on an open fire (for at least 30 min and at a temperature higher than 80 \({}^{\circ}\)C) followed by the first fermentation, in which the sugars of the grape must are oxidized to ethanol by means of yeast. Then, ethanol is bacterially oxidized to acetic acid in the second fermentation, mainly by the genera _Acetobacter_ and _Gluconacetobacter_ species [5]. Thisusually occurs in a series of five wooden barrels, where the final product passes in sequence through all barrels. The material for barrel production is, for example, mulberry, cherry, chestnut, oak, or juniper wood. Each of these barrels gives the vinegar a unique property. Traditional balsamic vinegas mature in barrels for at least 12 years (TBVM--affinato) or 25 years (TBVM--extravecchio). During this time, a replenishment process occurs, which means maintaining a constant level of intermediate in the barrels by transferring the liquid from one barrel to another. Liquid losses during evaporation are compensated by adding fresh must to the first barrel. Vinegar ages in a factory with uncontrolled temperature changes, while high summer temperatures support microbial activity and low winter temperatures support the evolution of taste. Grapes and all steps in the production process, including the aging of vinegar, must occur in the Italian provinces of Modena and Reggio Emilia. No other additives may be added during the maturation process and no techniques may be used to speed up the production process. The result is a dark brown liquid with a high density, sweet and sour, fruity, and complex taste [6; 7; 8; 9]. There are many differences between BVM and TBVM, including production, organoleptic properties, and economic aspects of the production. The production of BVM is simpler and involves mixing cooked grape must with wine vinegar, and with the possibility of adding a small amount of dye or caramel, which can give dark color and a sweeter taste to the product. As for the production time of BVM, the producers have a free hand here and it only depends on them how long they will let the vinegar mature. While BVM shows a variable degree of acidity and tastes more fruity and sweeter than regular wine vinegas, TBVM is characterized by low acidity and unique aroma, which is given by aging in wooden barrels. Another difference is in the volume of the bottle available in a store.