Detection threshold of chocolate graininess: machine vs human

Purpose Literature indicates that those solid chocolate particles cannot be detected by human beings that are smaller than a critical value between 25 and 35 mu m. Chocolate containing particles larger than this range is thought to be perceived as grainy. However, there does not seem to be any publication which justifies this threshold. Hence, the main aim of this work is to determine if the threshold at which particles can be detected is indeed 30 mu m. Design/methodology/approach Three dark chocolates containing solid particles of expected D-v,D-90 of 30 mu m, 40 mu m and 50 mu m were produced. Particle Size Distribution (PSD) was determined using static light scattering while hardness and melting behaviour were characterised using a penetration test and Differential Scanning Calorimetry (DSC), respectively. Sensory analyses were performed with a trained panel (n = 9). Findings PSD analyses indicated that the solid particle D-v,D-90 of the three chocolates were around 30 mu m, 40 mu m and 60 mu m, respectively. DSC measurements showed no significant difference in melting behaviour between the chocolates. Hardness measurements showed that the "30 mu m chocolate" was significantly harder than both the "40 mu m chocolate" and the "60 mu m chocolate", while trained panellists found that the graininess of the 60 mu m chocolate was significantly higher than that of the 40 mu m and 30 mu m chocolates. Practical implications These results suggest that particle size detection threshold is higher than 40 mu m. Chocolate manufacturers could thus increase the size of the biggest particles from 30 mu m to 40 mu m, leading to a decrease in production cost. Originality/value This is the first study to examine the particle detection limit of chocolate.