laboratory dryer at 60 C and ground in a universal shredder
with 5 mm mesh size;
- from the fruit and vegetable processing industry e apple
pomace and strawberry pomace from a hydraulic press, strawberry
pomace from a drum filter, orange and grapefruit peel,
carrot pomace from a screw extruder and beetroot peels. The
wastes were dried in a laboratory dryer at 60 C and ground in a
universal shredder for 30 s;
- from the oil industry e rapeseed cake obtained by cold extraction
in a single-screw extruder with a 8 mm nozzle diameter, at
screwspeed of 40 rpm. Rapeseed cake did not require additional
pretreatment;
- from the potato industry e peels of potatoes cv. Irga and Verona
and potato pulp. The materials were dried and ground as
described above;
- from confectionery and fat industries e walnut and hazelnut
shells, which were ground in a ball mill for approximately 2 min.
The moisture content of stored food wastes ranged from 3.4 to
7.4%.
The analyzed food wastes were supplied by industrial plants in
Poland (spent grain, apple and strawberry pomace, potato peel and
potato pulp), they were produced in laboratories of the Warsaw
University of Life Sciences (rapeseed cake) and households (beetroot
peel, carrot pomace, nut shells, orange and grapefruit peel).