Impact of roasting on the physicochemical characteristics of cacao beans and dark chocolate flavor profile

Chocolate flavor complexity depends on many factors, such as cacao bean genotype, environmental growing conditions, postharvest management, and chocolate production. It has been an object of study for more than 100 years, and over the years, more than 600 volatiles have been identified in cocoa flavor. However, it has been demonstrated that not all volatiles contribute significantly to the characteristic chocolate aroma. The cacao and chocolate market scenario has changed during the past fifteen years; product availability, diversity, and increase in quality contributed to structural changes in the chocolate industry, resulting in the specialty niche market development. Minimally processed chocolate, especially in terms of roasting and alkalization, has gained particular interest since it can potentially have positive health benefits. This trend in the chocolate industry will open new chocolate flavor profiles, where the inherent flavor and quality of cacao beans will play an essential role in consumer's preferences. However, there has been negligible research oriented to understanding the effect of the addition of minimally processed ingredients, such as unroasted cacao, on flavor, aroma, and physicochemical characteristics of dark chocolate. The overall objective of this project was to understand the effect of roasting on flavor aroma profile, physicochemical properties, and sensorial characteristics of dark chocolate. Cacao beans were roasted or dried to produce roasted and unroasted dark chocolate samples for analysis. Instrumental methods for physicochemical analyses included color evaluation, texture profile analysis (TPA), melting characteristics (DSC), rheology (Casson yield value and viscosity), and particle size. For flavor (aroma) analysis, the methods implemented included direct solvent extraction-solvent assisted flavor evaporation (DSE-SAFE), gas chromatography-olfactometry (GC-O), gas chromatography-mass spectrometry-olfactometry (GC-MS-O), and stable isotope dilution analysis (SIDA) coupled with headspace-solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). Additionally, Quantitative Descriptive Analysis (QDA) and Time-Intensity measurements were used for sensory evaluation. The roasting trial with the desired physicochemical characteristics received a thermal treatment of 2254.3 ± 331.1oC×min with 750 g mass load and 20 minutes roasting. The differences in aroma profile between roasted and unroasted chocolate included increased concentration of thermally generated volatile compounds and odor potency of odor-active aroma compounds in roasted samples. The main differences were observed in furanones, Strecker aldehydes, and pyrazines, which presented higher values in roasted chocolate. Additionally, volatiles developed during fermentation and drying, such as acetic acid, were preserved in minimally processed (unroasted) chocolate. Roasting also impacted physicochemical characteristics. Unroasted chocolate was brighter in color with lower red values compared to roasted samples. There was a significant effect of chocolate type (roasted or unroasted) for Casson yield stress, and a significant effect of both chocolate type and batch for Casson viscosity, where higher yield stress and viscosity measurements were observed in unroasted than roasted samples. Particle size was not impacted by chocolate type but was different among processing batches. For TPA, there was a significant interaction between chocolate type and production batch for hardness and chewiness. Sensory results revealed that roasting impacted aroma, texture, taste, and aroma-by-mouth characteristics in dark chocolate. Unroasted samples received higher intensity ratings for vinegar and cranberry aroma, sour and sweet taste, and cranberry aroma-by-mouth. In contrast, roasted chocolate was characterized by a higher intensity for roasted aroma, hardness, and roasted and cocoa aroma-by-mouth, compared to unroasted samples.LimitedAuthor requested closed access (OA after 2yrs) in Vireo ETD syste