Roasting cocoa beans lessens bitterness which boosts chocolate liking, says research

The study was published in the journal 'Current Research in Food Science'. The study involved 27 100 percent-chocolate preparations made from cocoa beans roasted at various intensities and 145 people who came to the center on five consecutive days, evaluating five different samples each day. 

The research confirmed that bitterness and astringency were negatively correlated to consumer liking, and demonstrated that those qualities in chocolate can be reduced through optimizing roasting, according to research team member Helene Hopfer, Rasmussen Career Development Professor in Food Science in the College of Agricultural Sciences. 

"More and more people these days are eating darker chocolates with less sugar and more cacaos because they are trying to cut down on sugar intake or they want to take advantage of perceived health benefits," Helene Hopfer said.

"Dark chocolate is particularly high in flavonoids, particularly a subtype called flavan-3 and their oligomers, which are all considered functional ingredients due to their associated health effects," she added. 

However, unsweetened chocolate is too bitter for most people to enjoy, so researchers experimented with roasting treatments to modify the flavor -- investigating more than basic tastes such as sour and bitter -- making it more acceptable for consumers, Hopfer explained.

For the study, research team member Alan McClure, founder of craft chocolate company Patric Chocolate and related consultancy Patric Food & Beverage Development, partnered with Hopfer and Penn State to characterize the flavor and acceptability of the chocolates. 

Part of his doctoral degree dissertation research, McClure chose cocoa beans from three origins -- Madagascar, Ghana and Peru, harvested in 2018 and 2019. 

He roasted and ground all samples into cocoa liquor at his factory in Columbia, Missouri, and then shipped the solidified 100% chocolate to Penn State, where he and Hopfer remelted and portioned out the chocolates into small discs for sensory evaluation. 

McClure found the reaction of study participants to his 27 100% chocolate preparations especially interesting, and he suggested that what he learned from this research will guide him, and roasting staff at other chocolate manufacturing companies, in creating future products through an increased scientific understanding of the complex changes resulting from cocoa roasting. 

In findings published in Current Research in Food Science, the researchers reported that more intense roasting conditions -- such as 20 minutes at 340 degrees Fahrenheit, 80 min at 275 F, and 54 min at 304 F -- all led to chocolate consumers finding unsweetened chocolate the most acceptable. 

Conversely, research participants did not find 100 per cent chocolate acceptable when made from raw or lightly roasted cacao, such as beans roasted 11 minutes at 221 F, or 55 minutes at 147 F.