Roasting and Cacao Origin Affect the Formation of Volatile Organic Sulfur Compounds in 100% Chocolate.

Chocolate is a highly appreciated food that develops its characteristic flavors in large part during the roasting of cacao beans. Many functional classes have been noted for their importance to chocolate flavor, including volatile organic sulfur compounds (VSCs). Despite this, the effect of roasting on the concentration of VSCs has never been thoroughly assessed. Here, we studied the effects of roasting temperature, time, and cacao origin on the formation of VSCs. Twenty-seven 100% chocolate samples made from cacao from three different origins and roasted according to an I-optimal experimental design were analyzed by comprehensive gas chromatography with sulfur-selective detection (GCxGC-SCD). For two compounds, dimethyl disulfide and dimethyl trisulfide, the effects of roasting time, roasting temperature, and cacao origin were modelled using response surface methodology and semi-quantified relative concentration. Overall, roasting increased the number of sulfur-containing volatiles present in chocolate, with a total of 28 detected, far more than previously thought. Increased roasting time and especially roasting temperature were found to significantly increase the concentration of VSCs (p < 0.05), while cacao origin effects were only seen for dimethyl disulfide (p < 0.05). The identity of most VSCs remains tentative, and more research is needed to unravel the impact of these volatiles on flavor perception in chocolate.

Optimizing consumer acceptability of 100% chocolate through roasting treatments and effects on bitterness and other important sensory characteristics.

Chocolate is a highly appreciated food around the world which is rich in polyphenols but usually sweetened to mask inherent bitterness and astringency. Here we aim to determine how roast time and temperature in cacao roasting affect bitterness intensity and consumer liking of chocolate. We have also determined the relationship between consumer liking and perceived bitterness, astringency, sourness, sweetness, and cocoa intensity. Unroasted cacao from three different origins was roasted according to a designed experiment into a total of 27 treatments which were evaluated for overall liking and sensory attribute intensities by 145 chocolate consumers. We demonstrate that bitterness, sourness and astringency of 100% chocolate can be reduced through optimizing roasting temperature and time. Reduction of bitterness, sourness and astringency were significantly correlated with increased acceptability of the unsweetened chocolate samples. Aside from roasting, cacao origin including base levels of bitterness, astringency, and sourness should also be considered when optimizing consumer acceptability. Perceived cocoa flavor intensity, being highly positively correlated to liking, is likely to also be an important consideration for raw material selection. As for optimal roast profiles, for the cacao origins in our study, more intense roasting conditions such as 20 min at 171 °C, 80 min at 135 °C, and 54 min at 151 °C, all led to the most acceptable unsweetened chocolate. Conversely, for the purposes of optimizing consumer acceptability, our data do not support the use of raw or lightly roasted cacao, such as 0 min at 24 °C, 11 min at 105 °C, or 55 min at 64 °C.

Quantitative analysis and response surface modeling of important bitter compounds in chocolate made from cocoa beans with eight roast profiles across three origins.

Eight different roast profiles for each of the three origins of cacao were prepared and made into unsweetened chocolate based upon an I-Optimal response-surface design for minimizing prediction variance. Quantitative chemical analysis of all chocolate treatments was performed with HPLC-DAD on six important bitter compounds (i.e., theobromine, caffeine, epicatechin, catechin, procyanidin B2, and cyclo(Proline-Valine)). Least-squares linear modeling was then performed. Using derived linear models, response-surface contour plots were produced to show predicted changes in the six bitter compounds over the entire experimental region. Significant and large decreases in concentration of epicatechin and procyanidin B2 were observed as roasting progressed, whereas for catechin and cyclo(Proline-Valine), significant increases were observed. Small yet significant theobromine and caffeine concentration increases were also observed with roasting, likely due to moisture loss. Some significant differences were also found between the cacao origins for all bitter compound concentrations except for cyclo(Proline-Valine), suggesting the importance of a survey encompassing a greater number of cacao origins in the future to obtain a more complete picture of the variation in bitter compounds in cacao due to origin. PRACTICAL APPLICATION: This research describes how roasting can be used to alter the concentration of bitter and sometimes astringent chemicals for several origins of cacao, which may be used to improve the sensory characteristics of dark chocolate.