## 3 Results and Discussion
### Integration into Circular Protein Systems  
The soy-based products presented in this study--expanded soybean cake (ESC) and full-fat soy (FFS)--are derived from locally grown European soybeans, free from the environmental burdens associated with transatlantic transport. Our internal carbon footprint analysis of raw soybeans from field trials revealed a low emission level of 89 kg CO2\({}^{-\text{eq}}\) per ton of dry soybean matter. Moreover, the processing approach described here utilizes exclusively physical methods, such as mechanical treatment and steam conditioning, without the use of chemical solvents (e.g., hexane). The production of both FFS and ESC follows a zero-waste principle, as no by-products are generated. An additional systemic issue identified by the authors and an industrial partner is the lack of industrial-scale processing aimed at protein quality rather than maximum oil yield. In this context, protein should be prioritized as the main product, while oil should be considered a secondary fraction--reversing the conventional paradigm in soybean processing. The compositional and functional properties of expanded soybean cake (ESC) position it as a versatile ingredient for multiple food and feed applications. With a protein content ranging from 37.40% to 38.98%, ESC aligns with current formulation standards for high-protein extruded foods, nutritional supplements, and meat analogs. The moderate residual oil content (11.56-13.33%) provides favorable textural and sensory attributes, contributing to improved palatability and processing behavior, particularly in clean-label product development. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Soy** & **Month** &
\begin{tabular}{c} **MAM** \\ **at 30 °C** \\ \end{tabular} & _Coli_ & **Y \& M** & _Enterobacteriaceae_ & **CPS** & _Salmonella_ \\ \hline \multirow{3}{*}{FFS} & 1 & \textless{}100 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & nd 1 \\  & 3 & 129 & \textless{}10 & \textless{}100 & \textless{}10 & \textless{}10 & nd \\  & 6 & 1624 & \textless{}100 & 113 & \textless{}10 & \textless{}10 & nd \\ \hline \multirow{3}{*}{ESC} & 1 & \textless{}100 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & nd \\  & 3 & \textless{}100 & \textless{}10 & \textless{}100 & \textless{}10 & \textless{}10 & nd \\  & 6 & 1000 & \textless{}10 & \textless{}100 & \textless{}10 & \textless{}10 & nd \\ \hline \hline \end{tabular}  
* \({}^{1}\)—not detected. MAMs—mesophilic aerobic microorganisms, Y&M—yeast and molds, CPS—Staphylococcus aureus.  
\end{table} 
Table 10: Microbiological counts ( cfu g\({}^{-1}\)) in FFS and ESC during storage for 1–6 months. The digestibility profile and reduced anti-nutritional factors (low trypsin inhibitor activity and phytic acid levels) make ESC highly suitable for age-specific functional foods, including formulations targeting elderly populations, sports nutrition, and clinical nutrition [28; 51]. Additionally, the elevated dietary fiber content (15.84-16.30%) supports glycemic regulation, promotes satiety, and contributes to favorable gut microbiota modulation [29; 31; 43]. The clean-label profile of ESC--free from synthetic binders or emulsifiers--addresses the growing consumer demand for minimally processed, transparent ingredients [52]. Its functional composition also facilitates the development of hybrid protein products that combine plant and dairy protein fractions to achieve optimal textural and nutritional balance [53]. ESC exhibits favorable rheological behavior during extrusion and thermal processing due to its unique matrix composition, which combines residual lipids, proteins, and fibers. The porous structure and partial oil retention enhance expansion properties, fiber integrity, and emulsification capacity, making ESC highly suitable for extruded snacks, protein-enriched bakery products, ready-to-drink beverages, and savory applications [54; 55; 56].