Chocolate rheological properties during storage and processing : A study examining yield value, viscosity and particle size distribution of chocolate duringstorage and processing

The aim of this project was to measure and analyze yield value, viscosity and particle size distribution for two types of chocolate. Based on the results the project would then set limit values for rheological parameters, yield value and viscosity for two types of chocolate, chocolate A and chocolate B. Furthermore, the project would also examine particle size distribution and how the particle size distribution is influenced when chocolate batches are stored in a tank. Chocolate mainly consists of cocoa butter, cocoa powder, milk powder and sugar. Cacao butter and cacao powder originates from the cocoa bean which comes from the Theobroma cacao tree in central and south America. Chocolate manufactory is a five-step process and involves dosage, mixing, refining and couching of products. For this project, rheological parameters for chocolate directly after production and finished chocolate products were compared. For measuring yield value and viscosity, a rheometer was used and for measuring particle size distribution, a laser diffraction analyzer was used. The results showed that yield value increases and viscosity decrease after storage and pumping and the limit values for chocolate A for yield value was 8.5-11 Pa and for viscosity was 1.5-1.9 Pa·s. For chocolate B limit values for yield value was 8-10.5 Pa and viscosity was 1.4-1.9 Pa·s. Furthermore, yield value, viscosity and particle size distribution showed clear trends between the values when chocolate is produced and after storage in tanks. In figures 17-20,22 and 24, the results also show that changes in chocolate production affect chocolate even in the process of making finished chocolate products.