Bitterness is generally considered a negative attribute in food, yet many individuals enjoy some bitterness in products like coffee or chocolate. In chocolate, bitterness arises from naturally occurring alkaloids and phenolics found in cacao. Fermentation and roasting help develop typical chocolate flavor and reduce the intense bitterness of raw cacao by modifying these bitter compounds. As it becomes increasingly common to fortify chocolate with `raw' cacao to increase the amount of healthful phytonutrients, it is important to identify the point at which the concentration of bitter compounds becomes objectionable, even to those who enjoy some bitterness. Classical threshold methods focus on the presence or absence of a sensation rather than acceptability or hedonics. A new alternative, the rejection threshold, was recently described in the literature. Here, we sought to quantify and compare differences in Rejection Thresholds (RjT) and Detection Thresholds (DT) in chocolate milk spiked with a food safe bitterant (sucrose octaacetate). In experiment 1, a series of paired preference tests was used to estimate the RjT for bitterness in chocolate milk. In a new group of participants (experiment 2), we determined the RjT and DT using the forced choice ascending method of limits. In both studies, participants were segmented on the basis of self-declared preference for milk or dark solid chocolate. Based on sigmoid fits of the indifference-preference function, the RjT was ~2.3 times higher for those preferring dark chocolate than the RjT for those preferring milk chocolate in both experiments. In contrast, the DT for both groups was functionally identical, suggesting that differential effects of bitterness on liking of chocolate products are not based on the ability to detect bitterness in these products.

中文翻译：

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巧克力牛奶中的拒绝阈值：分割的证据

苦味通常被认为是食物的负面属性，但许多人喜欢咖啡或巧克力等产品的苦味。在巧克力中，苦味来自可可中天然存在的生物碱和酚类物质。发酵和烘焙有助于形成典型的巧克力风味，并通过改变这些苦味化合物来减少生可可的强烈苦味。随着用“生”可可强化巧克力以增加健康植物营养素的含量变得越来越普遍，重要的是要确定苦味化合物的浓度变得令人反感的点，即使是那些喜欢苦味的人也是如此。经典的阈值方法侧重于感觉的存在与否，而不是可接受性或享乐主义。一个新的选择，拒绝阈值，最近在文献中有所描述。在这里，我们试图量化和比较添加了食品安全苦味剂（蔗糖八乙酸酯）的巧克力牛奶中排斥阈值 (RjT) 和检测阈值 (DT) 的差异。在实验 1 中，使用一系列配对偏好测试​​来估计巧克力牛奶中苦味的 RjT。在一组新的参与者（实验 2）中，我们使用极限的强制选择升序方法确定了 RjT 和 DT。在这两项研究中，参与者根据自我声明的对牛奶或黑巧克力的偏好进行细分。基于无差异偏好函数的 sigmoid 拟合，在两个实验中，偏爱黑巧克力的人的 RjT 比偏爱牛奶巧克力的人的 RjT 高约 2.3 倍。相比之下，两组的 DT 在功能上是相同的，