Effect of pH-shift processing combined with black chokeberry press cake on the structure and function of chicken by-products

• Protein isolation (CBPI) generated from the cross-processing of black chokeberry press cake and chicken by-product. • CBPI formed more cohesive structure with alkaline treatment. • Alkaline treatment and BCPC addition improve functional properties of CBPI. The pH-shift method selectively separates proteins from complex materials based on their isoelectric points. In this study, the technique was applied to chicken by-products (CBP) for protein extraction. To reduce oxidation in the resulting CBP protein isolates (CBPIs), black chokeberry press cake (BCPC)—an agricultural by-product—was added during processing. The results showed that alkaline treatment produced a more cohesive structure in CBPIs, while the addition of BCPC improved their otherwise deteriorated microstructure. Further analysis revealed that this structural improvement was linked to BCPC’s ability to reduce free sulfhydryl content and surface hydrophobicity. Compared to acid treatment, alkaline extraction enhanced the functional properties of CBPIs, including emulsification, foaming, and texture. Among them, the foaming capacity and foam stability of CBPI-12 were improved by 30.0 % and 44.4 %, respectively, compared to the acid treatment. Overall, combining pH-shift processing with BCPC not only minimized oxidation in CBPIs but also optimized their protein structure and functionality. This approach presents a promising strategy for sustainable resource utilization and efficient protein extraction.