Vacuum contact drying of dairy gel granules supported by in-line monitoring of the moisture content

By producing a storable intermediate during cheese processing by drying new flexibility is gained. Thereby, cheese can be produced detached from the production of intermediate granules and whey. The dairy gel granules tend to agglomerate without agitation and oil-out or plasticise at high temperatures making them a highly challenging product for drying. Contact drying in a modified Lödige ploughshare mixer was performed due to the possibility to apply sufficient agitation and to operate under vacuum. A design of experiments with varying granule types and jacket temperatures was performed and different responses analysed regarding drying efficiency. A higher drying temperature resulted in higher drying rates and consequently lower final moisture contents and a W values. For more insight into the drying process, two different in-line measurement techniques were installed and calibrated for monitoring of the moisture content. While the capacitive moisture measurement could not be calibrated, the near-infrared spectroscopy was successfully calibrated with a data selection via partial least squares regression with 2 nd derivative pre-processing and seven factors as a first step to a smart and dynamic drying process, where the drying parameters can be adapted to the current product properties of the granules. • A storable intermediate in the cheese production is received via vacuum contact drying in a modified Lödige ploughshare mixer. • Calibration of in-line monitoring system enables future control of the drying process of a highly challenging product. • Calibration of the near-infrared to the moisture content with partial least squares regression was successful using a selection of the data set.