Understanding the shear and extensional properties of pomace-fibre suspensions prior to the spray drying process

Pomace fibre is the left-over plant from juice processing which has several health-promoting properties. Fibre has potentially been recognized as a drying aid in the spray drying of fruit juice. In the present work, shear and extensional properties of different fibre suspensions were assessed and compared. Unlike fruit juice, which displays Newtonian behaviour, fibre suspensions exhibit shear thinning behaviour with dependence on the fibre fraction and aspect ratio and significant extensional properties as measured with a capillary break-up rheometer. The extensional properties of the fibre suspensions make it more difficult to atomize them. This study shows the importance of assessing both shear and extensional properties of fibre suspensions before incorporating them in spray drying.