Soybean meal is a class of by-products obtained from the processing of soybean products. Despite its high nutritional value, the presence of glycoside isoflavones limits human use of soybean meal. This study evaluated the effect of solid-state fermentation (SSF) with different edible mushroom mycelia (Pleurotus ostreatus, Hericium erinaceus, and Flammulina velutipes) on the proximate composition, antioxidant properties, and physicochemical properties of fermented soybean meal powder (SP). The results revealed that fermented SP had a higher nutritional value when compared to SP. P. ostreatus was the most pronounced among the three species. Crude protein content was found to have increased by 9.49%, while the concentration of glutamate and aspartic acid increased by 23.39% and 23.16%, respectively. SSF process significantly increased the total polyphenol content (TPC) and aglycone isoflavone content by 235.9% and 324.12%, respectively, resulting in increased antioxidant activity (evaluated by the DPPH, •OH, ABTS⁺ assays). Microstructural changes in fermented SP and nutrient degradation and utilization were observed. Thus, fermented SP can be used as a raw material with enhanced nutritional properties to develop new functional foods, such as plant-based foods represented by plant meat. It provides a promising approach for increasing the added value of soybean meal.

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.

The tiger nut (Cyperus esculentus L.) is an ideal raw material for oil extraction, but the starch-rich tiger nut meal, a by-product of oil extraction, has not been fully utilized. For this, starch was isolated from the tiger nut meal, then starch nanoparticles were prepared by gelatinization, ultrasonication and nanoprecipitation under different conditions. The preparation parameters were optimized by measuring the particle size with dynamic light scattering, and the physicochemical properties of native starch and nano starch were evaluated. The result showed that, compared to native starch, starch nanoparticle (nano starch) has a higher amylose content (39.05%), solubility (56.13%), and swelling power (58.01%). Furthermore, native starch and nano starch were esterified with octenyl succinic anhydride (OSA) respectively, conferring them amphiphilic properties. The effects of OSA modification on the resistant starch content, thermal properties, and microstructure of starches were characterized. The resistant starch content of tiger nut native starch increased by 10.81% after OSA modification, while the resistant starch content of OSA nano starch increased to 37.76%. Compared to native starch, gelatinization temperature of OSA nano starch decreased by 2.7 ℃ and nano starch decreased 5.68 ℃. Thereinto, OSA modified nano starch showed a unique microstructure, as a slender fiber structure and a regular oblate. The hydrophobic OSA groups aggregated to form hydrophobic cavities with a hydrophilic surface in the aqueous phase. The findings presented in this investigation would give a better understanding of the design and development of OSA nano starch and provide valuable guidance to further enhance the added value of tiger nuts and future applications in the food industry.