To address the poor extensibility of cellulose nanocrystal (CNC)/starch composite film, tiger nut starch (TNS), dialdehyde starch (DAS), and CNC were prepared from tiger nut meal and used to fabricate CNC/TNS composite films incorporated with different concentrations of DAS. The effects of different concentrations of DAS on the structure and properties of CNC/TNS composite films were investigated. The results showed that the characteristic peak corresponding to the aldehyde group appeared at 1730 cm^-1 in the Fourier transform infrared spectroscopy (FTIR). DAS exhibited an amorphous flake-like structure with a relative aldehyde content of 85.35%. The characteristic peak for aldehyde groups disappeared in the FTIR of the composite film, accompanied by a decrease in the hydroxyl absorption peak. The X-ray diffraction (XRD) pattern showed a reduction or disappearance of the crystallization peak corresponding to CNC, indicating that DAS was crosslinked with both CNC and TNS. After crosslinking, the intermolecular interactions in the composite films were enhanced, resulting in changes in the internal molecular structure and a 21.16%–83.31% increase in elongation at break. The films with DAS concentrations of 0.2% and 1.0% showed improved compatibility between CNC and TNS, as well as reduced roughness and thickness, and the oxygen barrier capacity increased by 14.14% and 51.37%, respectively. These findings demonstrate that DAS, at an appropriate concentration, can significantly enhance the overall properties of CNC/starch composite film.

Rice protein residue (RPR) and corn germ meal (CGM) are industrial by-products that are commonly applied as animal feed with low economic benefits. In order to develop a new approach for the resource utilization of grain protein residue, this study converted grain protein residue into edible mushroom protein through solid-state fermentation (SSF). To increase the biological efficiency of biotransformation, this study used Box Behnken design, combined with single factor experiments and response surface methodology, to optimize the SSF process parameters of edible mushroom mycelium. Optimal fermentation conditions were established considering both protein content and operational feasibility: RPR to CGM ratio of 4:1, utilizing the Pleurotus ostreatus strain, a fermentation duration of 14.5 days, a solid-to-liquid ratio of 1:0.8, and a loading capacity of 65.59 g. Fermentation under these optimized conditions yielded 73.34 g of protein per 100 g of RPR/CGM blend, which is 98.71% of the predicted value and represents a 1.28-fold increase from the initial protein content of 56.96 g/100 g. The amino acid evaluation results showed that the total amino acid content of the fermented protein residue increased by 12.88%, with a significant increase in the concentrations of glutamic acid and aspartic acid, which increased by 19.53% and 24.27%, respectively. In addition, the amino acid ratio coefficient score (SRC) and nutritional index (NI) were slightly higher, indicating a more balanced proportion of essential amino acids after fermentation. Additional research on the physicochemical properties of the protein residue post-fermentation revealed that the emulsifying capacity improved by 3.5% compared to the non-fermented sample. Edible mushrooms are a promising method for converting RPR and CGM into high-protein raw materials.