Microstructure and mechanical properties related to particle size distribution and composition in dark chocolate

Abstract

Composition in dark chocolate was varied and the effects determined on microstructure, using light microscopy, and mechanical properties of molten and tempered chocolates, using a TA.HD Plus Texture Analyser. Compositional parameters were particle size distribution (PSD) (D90 of 18, 25, 35 and 50 μm), fat (25%, 30% and 35%) and lecithin (0.3% and 0.5%) contents. Micrographs revealed wide variations in sugar crystalline network structure and inter-particle interaction strengths related to PSD and fat level. Samples containing 25% fat had more crystal agglomerates, well flocculated with greater particle-to-particle interaction strengths than those with higher (30% and 35%) fat contents. Increasing the D90 to 35-50 μm caused broadening of the PSD, with particles becoming coarser, which were similar at all fat levels. Mechanical analysis showed that PSD, fat and lecithin content significantly influenced firmness of molten chocolate and hardness of solid (tempered) chocolate with significant interactions among factors. Particle size was inversely correlated with firmness (1235-173 g) and hardness (7062-5546 g). Greatest effect of PSD was with 25% fat and 0.3% lecithin. With higher fat and lecithin contents, the PSD influence was reduced. It was concluded that PSD, fat and lecithin contents and their interactions were central to mechanical properties of dark chocolates

Influence of calcium fortification on physical and rheological properties of sucrose-free prebiotic milk chocolates containing inulin and maltitol

“…Previous studies have also shown that SSA is inversely correlated with the different components of the PSD (Afoakwa et al 2009;Beckett 1999;Sokmen and Gunes 2006;Ziegler and Hogg 1999), as was observed in this study. As a result, it was concluded that a variation in PSD may occur depending on the CaCO 3 content of chocolate, and that it is possible to observe a variation in the rheological, sensory and textural properties of the product due to this PSD variation.…”

“…Traditionally, continental European chocolate has been described as having a fineness of 15-22 μm particle diameter, while North American chocolate has a corresponding value of 20-30 μm (Afoakwa et al 2009). Typically, values around 20 μm are used for standards (Schumacher et al 2009).…”

“…Smaller particle sizes in chocolates are known to improve sensory properties (Ziegler et al 2001). In previous studies, it has been reported that the rheological properties of chocolate are affected also by processing (refining, conching and tempering) as well as composition (amount of fat, amount and type of emulsifiers) (Afoakwa et al 2009;Schantz and Rohm 2005;Varveck 2004). …”

Sensory profiles of chocolates produced from cocoa cultivars resistant to Moniliophtora Perniciosa

“…According to the QDA, the chocolate samples from the PH16 cultivar were characterized by significantly (p<0.05) greater firmness than the other two samples. The texture is one of principal factors used to evaluate the quality of the products by the consumers, and two other important factors are the appearance and flavor (AFOAKWA et al, 2009).…”

Tensile Strength of Dark Chocolate

“…These properties are studied using many different experimental methods. A penetration test using a thin probe is an empirical method of assessing the mechanical properties of chocolate or confectionery products (Liang and Hartel, 2004;Do et al, 2007;Afoakwa et al, 2008Afoakwa et al, , 2009). This method has been used to study the effect of composition, particle size distribution, fat crystallization behaviour and tempering on the mechanical properties in chocolate bars (Afoakwa et al, 2008(Afoakwa et al, , 2009.…”