University of Missouri-Columbia student Alan McClure, PMCA’s 2018-2019 grant-in-aid recipient, has completed his research project, “Optimization of Bitterness in Chocolate Through Roasting with Analysis of Related Changes in Important Bitter Compounds.”

Chocolate is made from the fermented, dried and roasted seeds of the Theobroma cacao tree, an important agricultural food crop which contains bioactive flavonoid polyphenols with beneficial health effects. These include improvement of antioxidant status, positive impacts on cardiovascular health and endocrine system function, association with cancer prevention, LDL cholesterol reduction and correlation with reduction of obesity and related conditions. 

However, products which have the highest levels of cacao flavonoids of all eating-chocolate, such as high-cacao-percentage dark chocolate, are known to be quite bitter, a taste modality that is not readily appreciated by consumers.

Much was still to be learned about the variation in bitter-compound composition in cacao and related sensory characteristics, within and between different cacao origins and across different roast profiles. This, combined with a growing desire for healthy, functional versions of foods such as chocolate, made research into the impact of cacao roasting on consumer perceptions of bitterness, and overall liking in chocolate and the underlying chemical changes, all the more timely.

This research project has resulted in findings covering a significant range of chocolate topics. A new method for simultaneous extraction and analysis of important bitter compounds in cacao and chocolate was developed, and a custom response-surface methodology (RSM)-based design for roasting treatments, with emphasis on I-optimality for minimizing prediction variance, was created. Chemical and sensory analysis of the roasted chocolate treatments were carried out, followed by in-depth data analysis and interpretation of these data in the context of current chocolate science.

McClure’s advisor on this project is Dr. Ingolf Grün. PMCA members can visit to download the final paper.