Pelleting properties and pellet quality of apple pomace

Abstract

Apple pomace (AP) is the main by-product of apple juice production. It is a residue after pressing of apples for juice extraction. AP is an organic material, with high moisture and sugar content, therefore its direct disposal on landfills or land spreading causes serious environmental pollution. One of the solutions for further exploitation of AP could be its utilization as animal feed. However, fresh AP is quite perishable, and it must be preserved in order to be stored and used over a long period of time. The aim of this research was to investigate the possibility to transform AP to a stabile form which would be acceptable for feed manufacturers in terms of stability, storage and handling. For this purpose, pelleting process was used and pelleting properties of AP were evaluated. Before pelleting, dried AP was divided into three batches, which were conditioned only by water addition in order to achieve different moisture contents of the material: 10% of moisture for the first batch, 13% for the second batch and 16% for the third batch. According to the obtained values for Pellet Durability Index (PDI) and pellet hardness, pellet quality for all examined AP batches was very high. Increased moisture content of AP led to the reduction in energy consumption of the pellet press, thus providing energy saving in the pelleting process. Pelleting process also caused strong increase of AP bulk density which is positive in terms of transportation and storage.