Material properties of cocoa butter emulsions: Effect of dispersed phase droplet size and compression speed on mechanical response

Abstract

Sample H/d = 1.6 Deformation mode Schematic CB fat crystal Dispersed water droplet Applied Load Fat crystaldroplet intact solid bond Fat crystaldroplet broken solid bond: Fracture Initiation Fracture propagation lineWater-in-cocoa butter (CB) emulsions material properties were investigated using uniaxial compression test. Emulsions containing 20% (wt%) water and with a range of droplet size were manufactured to assess the role of defect size on emulsions mechanical properties. Although differences were not significant within the tested droplet size range, results showed a decreasing trend in the values of mechanical parameters at fracture with increasing structural defect size. The mechanical response of bulk CB and emulsions was also investigated at different compressive rates. Materials visco-elastic behaviour was confirmed by their strainhardening behaviour at increasing test speed with bulk CB always displaying the highest mechanical strength. In the light of these results and microscopy evidences, it was hypothesised that droplets are only partially bonded to the CB network therefore playing a stressconcentration role by promoting fracture initiation. The addition of water droplets also resulted in a reduction of the overall network internal degree of connectivity: when large deformations are applied, droplet-matrix de-bonding occurs at the particle-fat network interface promoting fracture propagation and thus explaining the weakening structural effect of droplets.

Influence of Emulsifiers and Dairy Ingredients on Manufacturing, Microstructure, and Physical Properties of Butter

“…Presence of non-fat components and emulsifier additives in bulk fat or emulsions has been known to induce a heterogeneous nucleation process and a mechanism of secondary nucleation [19][20][21]. Besides, depending on the molecular structures and mobility, emulsifiers at the water/oil interface can affect the droplet-matrix interactions, and in consequence, mechanical properties of the product, which has been examined in water-in-oil emulsions [17,22,23] and protein gels [24,25]. However, the role of dairy-derived ingredients has not been explored much in the same light for their impact on the macroscopic consistency of butter.…”