Quantitative analysis of hydrocolloids in food systems by methanolysis coupled to reverse HPLC. Part 2. Pectins, alginates and xanthan

A procedure for quantitative determination of pectins, alginates and xanthan, in complex food systems, is presented. It involves three main steps: (i) homogenization and freeze-drying of food sample; (ii) direct methanolysis of dried sample; (iii) reverse HPLC analysis of specific constituent sugars released from hydrocolloids. The proposed method allows the determination of hydrocolloids in the presence of the other ones, namely in the presence of gelling carrageenans. Recoveries were generally higher than 80% with a detection sensitivity of about 0.03%. Hydrocolloids may be directly determined in complex food products such as yoghurt, gelling milk or pâte without need for prior delipidation, deproteinization or hydrocolloid extraction.