Transforming the odor profile of perennial ryegrass protein and surplus bread crusts through solid-state fermentation

The growing demand for sustainable, high-quality protein sources is driving the development of novel foods. In this study, the underexplored combination of surplus bread crusts (BC), a major source of food waste, and perennial ryegrass (PRG), a traditional forage crop with underexploited potential for human nutrition, was used as a potential substrate in the production of protein-rich novel ingredients for human consumption. The BC substrate supplemented with crude PRG protein was fermented with Rhizopus oligosporus, Aspergillus oryzae or Neurospora intermedia for up to 72 h to enhance the nutritional and olfactory qualities biologically. After solid-state fermentation (SSF), the volatile organic compounds (VOCs) that were present were captured by solid-phase microextraction followed by gas chromatography-mass spectrometry. Over 150 compounds were identified at different stages of SSF and correlated to specific fungi or substrates via principal component analysis (PCA). These results provide an understanding of the composition of VOCs throughout fungal SSF and prove its capacity to improve the odor of forage crops for novel food production.