In a paper published in the Journal of Food Science, IFT scientists investigated how those preferring milk chocolate and those preferring dark chocolate were able to tolerant bitterness in chocolate.
The rejection threshold: how much is too much?
The researchers applied a new psychophysical method called the rejection threshold, which determines levels of tolerability. It differs from other methods that simply detect off-flavors.
Study author John Hayes told ConfectioneryNews.com that the method could benefit chocolate manufacturers in two ways.
“First, we believe this technique has broad application for quality control in chocolate. It could be applied to any potential off flavor (aka 'taint') becomes undesirable with increasing concentrations, such as bitterness, sourness, smokey, hammy, etc.,” he said.
“Second, we demonstrate that this technique can distinguish between market segments. This may inform product development efforts by enabling developers to target specific segments based on their rejection thresholds,” he continued.
He gave an example of a chocolate product with enriched cocoa polyphenols that could be tailored for ‘dark chocolate lovers.’
“Downstream, this method could also be using to inform marketing efforts of these specialized products,” he said.
Rejection vs detection
The rejection threshold differs to commonly used ‘detection thresholds’, which simply identify off-flavours without specifying how much of an off-flavor is acceptable.
For example, a wine with a hint of cork may give a strange flavor, but it may only be a small amount and still tolerable.
“Using a detection threshold to try to determine acceptability ignores subtle but important distinction,” said the authors.
Method & findings
Eight-five adults were given samples of milk chocolate compound coating, with a bitter flavor added through different concentrations of sucrose octaacetate (SOA), a highly bitter compound.
The concentrations of SOA varied from 0 μM (micromolar) to 120 μM.
Participants were asked to identify a preference for either dark or milk chocolate and their eating style: chewer, quick chewer or melter.
Those preferring dark chocolate had higher rejection thresholds, meaning they were less likely to reject high concentrations of SOA-embued chocolate compare to milk chocolate lovers.
Dark chocolate connoisseurs could handle two times the SOA concentrations (113 μM) of milk chocolate lovers.
The overall average rejection threshold was 81.5 μM.
The study authors found no link between eating style and the rejection threshold.
The research was funded by the Pennsylvania Manufacturing Confectioners Association (PMCA).
Journal of Food Science, Vol. 77, Issue 10, S390–S393, Oct 2012
‘Rejection Thresholds in Solid Chocolate-Flavored Compound Coating’
Authors: Meriel L. Harwood, Gregory R. Ziegler, John E. Hayes