Identification of Volatile Contributors to Bitterness in Chocolate
Open Access
- Author:
- Wiedemer, Aaron
- Area of Honors:
- Food Science
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Helene Hopfer, Thesis Supervisor
Chris Sigler, Thesis Honors Advisor - Keywords:
- Chocolate
Flavor Chemistry
Odor Induced Enhancement
Bitterness
Sulfur
Volatile Organic Compounds
GC-MS
GCxGC-MS
GCxGC-SCD - Abstract:
- Chocolate is a highly appreciated food around the world whose unique flavor is due to a complex mix of both volatile and non-volatile compounds. Bitterness is a basic taste that is extremely important to chocolate flavor and, although has been shown to be affected by other modalities, has been thought to have been primarily caused by non-volatile compounds in chocolate. Odor induced taste effects occur when odor-active volatile organic compounds in foods change the perception of specific tastes, and while odor induced taste effects have been well studied for tastes such as saltiness and sweetness, just a few studies report odor induced effects on bitterness. Therefore, the goals of this study are to 1.) investigate if and how chocolate odor affects overall perceived bitterness and 2.) present a list of potential chemical compounds that may be causing odor induced effects on overall perceived bitterness. This is the first time any volatile contributors to bitterness have been explored in chocolate. In addition, volatile sulfur compounds, particularly dimethyl disulfide (DMDS) and dimethyl trisulfide (DMTS) which are produced during the roasting process, have been noted for their importance to chocolate flavor. Despite this, the effect of roasting on these compounds has never been thoroughly studied, and so a third goal of this research was to investigate how roasting of cocoa affects volatile sulfur compound composition in chocolate. Using chocolate samples made from cacao from three different origins and roasted according to an experimental design (McClure et al., 2021) we found evidence for odor induced effects on perceived bitterness in chocolate through human sensory analysis. To identify potential volatiles causing this effect, chocolate samples were evaluated using gas chromatography-mass spectrometry (GC-MS) and raw data was analyzed using PARADISe to identify and semi-quantify compounds. Two primary lists of compounds were identified via correlation and partial least squares regression analysis, with 2,3-Butanedione and Ethyl Butanoate being the two compounds with significant correlation values to overall bitterness, VIP scores of over 1.5, and selectivity ratios of over 10. Volatile sulfur compounds were evaluated in the samples using comprehensive gas chromatography with mass spectrometry and sulfur selective detection (GCxGC-MS/SCD). Semi-quantified volatiles were analyzed by ANOVA and multivariate statistical methods to determine the effect of roasting and origin on sulfur compounds. Both the concentration and diversity of sulfur compounds increased significantly (p<0.05) by all three experimental factors, with roasting temperature by far exceeding the effects of roasting time and cacao origin. These findings warrant future investigations into the effect of sulfur compounds on the sensory perception of chocolate in the future.