Controlled fluidized bed drying of dairy gel granules using in-line monitoring of the moisture content

Smart and dynamically controlled drying enables processing of challenging materials. Dairy gel granules are an intermediate material during cheese production, which can be dried for more flexibility regarding place and time of production. However, agitation is necessary during drying due to the granules’ tendency to build agglomerates, as well as low temperatures due to risk oiling-out and plasticizing at high temperatures. The resulting long and inefficient fluidized bed drying process shall be improved by using in-line monitoring of the moisture content via a near-infrared (NIR) sensor calibrated with partial least squares (PLS) regression. Using that moisture content and the correlation to a changing temperature of the irreversible gel sol transition, the drying temperature can be adapted in-line to be just below that temperature. Comparison of these dynamically controlled drying trials to reference trials with a static drying temperature showed drier products within the same drying time, ergo higher drying rates. Thereby, the feasibility of the concept could be proven.