Thermoplastic biofilms obtained from an arabinoxylan-rich fraction from brewers' spent grain: physicochemical characterization and thermal analysis

Brewers' spent grain is an important source of non-starch polysaccharides, such as arabinoxylans. In this paper, a fraction rich in arabinoxylans was extracted from brewers' spent grain (BSG-AX) by alkaline medium; was characterized by FTIR spectroscopy, scanning electronic microscopy (SEM), and zeta potential; and was used to prepare fourteen thermoplastic films by addition of two plasticizers (glycerol and polypropylene glycol) and a defoamer agent (coconut oil). All films were characterized by FTIR spectroscopy, SEM, and thermogravimetric analysis (TGA). Activation energy (E-a) of the thermal film's degradation were determined using four models (Broido, Horowitz-Metzger, Coats-Redfern, and Kissigner-Akahira-Sunose), which provide overall kinetic data. Likewise, microbiological analysis of films was performed for assessing their safety. FTIR spectra of BSG-AX films confirm the presence of distinctive functional groups for arabinoxylan, whereas their morphology shows a homogeneous surface structure. Zeta-potential measures suggest that BSG-AX can be considered as a neutral polysaccharide between pH 3 to 10 (values from - 3.44 to - 9.17 mV). Two stages of mass loss were observed in the plasticized films and three for the control (at 113-174 degrees C, 215-350 degrees C, and 487-598 degrees C). The addition of the plasticizer and defoamer agents increases the E-a of the films; namely, the films show greater thermal stability. Besides, the microbiological analysis suggests that the BSG-AX films are safe (absence of total coliforms and 10(2) CFU g(-1) of aerobic mesophylls). In conclusion, plasticized films prepared with BSG-AX have characteristics such as resistance to a wide range of temperatures and can be used as packaging materials.