Effect of pH on phosphorylation of potato protein isolate

Potato protein isolate (PPI) was phosphorylated with sodium trimetaphosphate (STMP) at ambient temperature and various reaction pH (5.2, 6.2, 8.0 and 10.5) to improve the functional properties without impairing the nutritional availability. Changes in chemical composition (total and coagulable protein content, ash and minerals content and amino acid composition), functional properties (protein solubility index, emulsifying activity and foaming capacity, water and oil absorption capacity) and phosphorus were determined. The chemical composition and functional properties of phosphorylated potato protein isolate (PP-PPI) were significantly different (p < 0.05). The PP-PPI at pH 5.2 was characterised by the highest content of all amino acids, whereas, PP-PPI under alkaline conditions (pH 10.5) caused decrease in these compounds. PP-PPI at pH 8.0 had the highest oil absorption capacity, emulsion activity and foam capacity, whereas, PP-PPI at pH 10.5 had the highest WAC.

► PP-PPI modified at pH 5.2 was characterised by the highest content of amino acids.
► PP-PPI at pH 8.0 had the highest phosphorus content.
► The highest WAC was observed for PP-PPI, phosphorylated at pH 10.5.
► PP-PPI phosphorylated at pH 8.0 showed the highest emulsion activity.