Recovering proteins from potato juice by complexation with natural polyelectrolytes

Summary Potato proteins ( PP ) in the lab‐made potato juice consists of patatins (38.1%), protease inhibitors (56.7%) and other high molecular weight proteins (5.1%) as characterised by Tricine‐ SDS ‐ PAGE and MALDI ‐ TOF / TOF ‐ MS . To recover PP from potato juice, the complex behaviours of PP with several natural polyelectrolytes as a function of pH and protein to polyelectrolyte ratio ( R PP /Polysaccharide ) were studied by turbidimetric titration. Results indicated that the turbidity curves of PP ‐polysaccharides displayed a shift to higher pH for chitosan and lower pH for anionic polysaccharides with the decreasing of R PP /Polysaccharide . Chitosan could be used to selectively recover patatin with the purity of 88.6%, and the highest protein yield (51.9%) was achieved at pH 6.0 and R PP/chitosan of 1:2. Carrageenan, one typical anionic polysaccharide, could recover all the PP in potato juice at pH 3.5 and R PP /carrageenan of 2.5:1 with no special protein selectivity.