Effect of the particle size of spray-dried milk powder on some properties of chocolate

Spray-dried milk powders have a median particle size of 30-80 mum. Roller-dried powder particles, which are larger (about 150 mum), are preferred for chocolate making. Spray-drying variables were therefore studied to produce larger powder particles for chocolate. The particle size of the spray-dried powders increased with increasing size of the spray nozzle orifice used. The free-fat content, vacuole volume and insolubility index of the powders increased at the above normal air outlet temperatures used to dry the large powder particles. Vacuole volume and moisture contents typical for spray-dried powders were obtainable at air outlet temperatures up to 90degreesC. The particle size of the chocolate mix after refining and the Casson yield value of the chocolate after conching reached minimum values using spray-dried powders with median particle size values of 132-162 mum. These minimum values in the chocolates were also correlated with higher contents of free-fat and lower vacuole volumes in the powders. The spray-dried powders produced good quality British-style chocolates, where the particle size after refining is conventionally <26 μm, but not continental chocolates, where the particle size should be <20 mum.