Cardoon seed oil cake proteins as substrate for microbial transglutaminase: Their application as matrix for bio-based packaging to extend the shelf-life of peanuts

Abstract

In this study, microbial transglutaminase (mTGase), an enzyme that can alter the biological properties of various proteins by creating isopeptide bonds between glutamine and lysine residues, was tested for the first time on proteins from cardoon oil cakes (CPs). mTGase crosslinked CPs were used as matrix for preparing bio-based materials further evaluated for their technological characteristics, such as mechanical and hydrophilicity behavior, gas barrier and thermal properties, color and opacity. All the performed analyses demonstrated that the microbial enzyme affected the film features by making them more resistant (Young's modulus and tensile strength were 52 MPa and 1.7 MPa for the film manufactured in the absence of enzyme and 98 MPa and 3.3 MPa for the crosslinked film, respectively), less hydrophilic and permeable to gases likely due to the formation of a more compact structure due to isopeptide bonds formed by mTGase as demonstrated by scanning electron microscope analyses. For example, the water vapor permeability of neat films was 8.37 g mm m−2 d−1 kPa−1, whereas that performed by mTGase-crosslinked material was equal to 5.16 g mm m−2 d−1 kPa-1. Bio-disintegration test proved that the materials were able to be decomposed under soil-like conditions. Thermal analyses also showed that the crosslinked materials had a matrix more stable over different temperatures, as a function of enzyme concentrations. Finally, the prepared bioplastics were used as sachets to protect peanuts chosen as an example of a high-oil content snack. The findings revealed that during a 30-day period, peroxidase levels and water content of peanuts packed in sachets manufactured from mTGase-crosslinked CP were lower than those packed in neat film and unpacked, and similar to those packed in LDPE, indicating that the novel bioplastics may be employed as biodegradable materials to prolong the shelf-life of such food goods.