Effects of different drying methods on drying characteristics and quality of silage Broussonetia papyrifera L.

Abstract

The effects of hot air drying (HAD), vacuum drying (VD) and pulsed vacuum drying (PVD) on moisture ratio, drying rate, effective diffusion coefficient, activation energy, color, ash, protein, acid detergent fiber, neutral detergent, fiber total digestible nutrients ( TDN ) and relative feeding value ( RFV ) of silage paper mulberry were investigated, and optimal drying processes were developed using entropy weight method. Results show that the drying characteristics of silage paper mulberry, which can be seen as particle packed porous media, undergoing different drying methods exhibit similarities to those of conventional hygroscopic porous media. In terms of quality, noticeable browning occurs when the silage paper mulberry is subjected to HAD at 70 °C or higher, whereas no significant color change is observed under VD at temperatures of 80 °C or lower. Increasing the material thickness leads to higher TDN and RFV after HAD, but higher pressures and drying temperatures resulting in reducing in RFV after VD or PVD. The optimal drying process for HAD is 3 cm, 70 °C, 20%, 1 m/s and it is recommended to use 3 cm, 7 kPa and 70 °C for VD. As for PVD, the conditions are same as VD and using pulsation ratio of 50:5 min. • PVD does not further improve drying ratio for particle packed porous media than VD. • Noticeable browning occurs when drying temperature over 80 °C. • Increasing the thickness leads to higher TDN and RFV for HAD. • Higher pressures or drying temperature resulting in RFV reducing undergoing VD or PVD. • Optimal HAD process is 3 cm, 70 °C, 20%, 1 m/s, for PVD is 3 cm, 7 kPa, 70 °C, 50:5 min.