# Comparison of the Chemical and Sensorial Evaluation of Dark Chocolate Bars
## 1 Introduction  
Flavor is undoubtedly the most important chocolate attribute in consumers' experience. As a complex combination of taste, aroma, and chemesthetic perceptions originating from the mouth and nasal area, many parameters concur to its development [1, 2]. The quality of the starting raw material is of the utmost importance; cocoa varieties are, indeed, characterized by enormous genetic diversity, which ultimately confers peculiar aromatic notes to the different cultivars, classified based on their overall quality as \"bulk\" and \"fine aroma\" beans [3, 4]. The cocoa market for chocolate mass production is dominated by the \"bulk\" cocoa, since these _Theobroma cacao_ L. varieties are more resilient to diseases and have larger yields. However, in recent years, especially in central Europe, chocolate is more and more consumed as \"gourmet\" food, with higher quality standard requirements from the average consumers' market, as well [5]. In general, consumers tend to perceive cocoa beans coming from a single geographical region as an indication of higher quality of the product, but this is considered misleading by a lot of chocolate manufacturers since the _terroir_ greatly varies within the same country, as well [5]. The subsequent manufacturing phases of the primary and secondary processing have a great influence on the quality of the final product. The flavor precursors are, indeed, developed during primary processing phases (pulp management, fermentation,and drying); the secondary phases (alkalization, roasting, grinding, etc.) complete the transformation of the precursors into the final flavor notes, commonly associated which chocolate [1,3]. Moreover, the processing method used determines other favorable sensory characteristics of chocolate, such as its appearance and texture, the latter perceived both on the lips and in the mouth [2]. Chocolate manufacturers and chocolatiers mainly rely on the percentage of cocoa solids to define the quality of chocolate, considering values of 75-85% as indices of a more sophisticated aroma [5]. The average consumers' preference, however, is more addressed by chocolate bars with a lower cocoa solids content, generally between 50% and 60% [6]. The analysis of volatile organic compounds (VOCs) by headspace solid phase micro-extraction (HS-SPME) is a fast, easy, and reliable method to assess their emission from chocolate bars of different origin. It allows identification of chemical compounds composing the aroma bouquet of the product, as perceived at room temperature as consumers' smell impression, reproducing the most similar olfactory perception conditions [7]. The starting material and the primary processing of the cocoa beans ensure the presence of aroma precursors, while the secondary processing develops the characteristic volatiles involved in chocolate aroma [1]. [PERSON] [8] identified over 600 volatile compounds involved in chocolate aroma, among which the vast majority belong to the pyrazines chemical class [9, 10, 11], followed by esters [9, 12, 13]. The aroma of chocolate, however, is quite complex, as it involves a wide variety of chemical groups, such as alcohols [4, 11, 14], aldehydes [9, 11, 15], and ketones [11, 12, 15]. Pyrones, furanones, and acids add depth to the bouquet composition, and are frequently reported as emitted volatiles, however their presence is generally perceived as pleasant only when in low relative abundances [9, 11, 16]. The chemical assessment alone, however, does not take into account the human perception, which is far more complex since it is the result of a combination of chemical and physical stimuli. Electronic noses are widely used in food analysis, but the obtained results generally do not correlate very well with the sensorial analysis performed by a panel test, unless used to look for a specific aroma note in a matrix [17].