Effect of milk composition on spray-dried high-fat milk powders and their use in chocolate

High-fat and skim-milk powders were produced under constant processing conditions from Spring and Autumn herd milks. The influence of the seasonal variation in protein and solid-fat contents at 10degreesC of these milks on some properties of the milk powders was determined. The free-fat content and the median particle size of high-fat milk powders were significantly (P<0.05) affected by the protein content and solid-fat content of the milk. There was a curvilinear relationship between the median powder particle size and solid-fat content at 10°C of the milks. Milk composition did not significantly affect the properties of the skim-milk powders studied. The results showed that it is possible to predict the free-fat content of high-fat milk powders from the protein and solid-fat content of the milks used. Relationships between the spray-dried high-fat milk powder properties and the rheology of milk chocolate at the end of conching and its final hardness were then determined. Eleven spray-dried high-fat milk powders were blended with skim-milk powders to give a 26% fat ingredient for chocolate manufacture. The Casson viscosity (Pas) of the chocolate at 40°C at the end of conching decreased as the free-fat content increased (P<0.01) and as the powder median particle size increased (P<0.05). The Casson yield value (Pa) at 40°C at the end of conching decreased (P<0.01) as the solid fat contentat 10degreesC increased. The hardness of the tempered milk chocolate was significantly reduced as the free-fat content increased (P<0.05) and as the particle size increased (P<0.05). It was concluded that spray-dried high-fat milk powders with different properties can be used to make chocolates with a range of viscosities and yield values for different end uses.