Novel drying treatment to stabilize bilberry, blackcurrant, and cloudberry press cakes: Dryer performance and product quality characteristics
2020
Grimm, Alejandro | Nyström, Josefina | Mossing, Torgny | Östman, Ulla-Britt | Geladi, Paul
In this paper, continuous cyclone drying was compared to conventional batch fixed-bed convective drying of bilberry (Vaccinium myrtillus L.), blackcurrant (Ribes nigrum L.), and cloudberry (Rubus chamaemorus L.) press cakes from berry juice production. When the cyclone dryer was operated at a low feeding rate (2 kg/h), a drying air temperature of ~90 °C, and an inlet-air velocity of ~110 m/s, the dry matter content of the press cakes increased from 23.9 to 85.3 wt% for bilberry, 44.3 to 80.6 wt% for blackcurrant, and 36.4 to 68.4 wt% for cloudberry. The residence/drying time of feedstock particles inside the cyclone dryer when using the process variables mentioned above was approximately 2 s. The product from cyclone drying of cloudberry consisted mainly of seeds; therefore, only bilberry and blackcurrant press cakes were tested in fixed-bed drying. Average convective fixed-bed drying rates were lower than those for cyclone drying. The total polyphenol contents in fixed-bed and cyclone dried samples at the same drying air temperature was close. For bilberry ~8.6 freeze-dried, ~7 at 40 °C, ~5 at 90 °C, and for blackcurrant ~8 freeze-dried, ~7 at 40 °C, ~6 at 90 °C given as g GAE/100 g press cake d.b.
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