Acid precipitation salting out as an efficient strategy for high purity potato trypsin inhibitor recovery

Potato trypsin inhibitor (PTI) is a high-value bioactive protein from potato processing wastewater with potential applications in functional foods and nutraceuticals. This study systematically compared three extraction strategies-acid precipitation-salting out, direct resin adsorption, and zinc ion precipitation-for PTI recovery from simulated potato processing wastewater. Acid precipitation-salting out emerged as the most effective approach, yielding PTI with high purity (63.62% protein), superior specific activity (533.06 TIU/mg), and enhanced structural stability evidenced by high β-sheet content (48.09%), narrow particle size distribution, and elevated zeta potential. The extracted PTI exhibited favorable emulsifying capacity (66.68%), foam stability exceeding 80%, broad pH stability, and moderate resistance to simulated gastrointestinal digestion (73.98% activity retention). In contrast, resin adsorption achieved higher yield but lower purity and functionality, while zinc ion precipitation introduced significant heavy metal residue risks. This work establishes acid precipitation-salting out as a scalable strategy for high-quality PTI extraction and highlights its dual functionality as a bioactive and techno-functional ingredient, supporting sustainable valorization of potato processing waste.