Extraction of sunflower head pectin with superfine grinding pretreatment.

Effect of superfine grinding on pectin extraction was investigated. Sunflower heads were grinded into microparticles of ~50 μm, thus pectin chains were fully exposed due to cell wall breakdown. A good pectin yield of 14.5 ± 0.36% (w/w) was subsequently achieved at mild conditions (pH 5.0, 25 °C, 2 h) associated with 0.8% (w/v) sodium citrate (SC). However, the molecule weight of pectin was greatly reduced (Mw = 7.87 ± 0.21 kDa) due to the action of endo-pectinases. With heating (pH 5.0, 85 °C for 20 min, 25 °C for 1.5 h) the endo-pectinases were effectively inhibited, thus Mw was increased to 338.07 ± 12.37 kDa. With superfine grinding, pectin extracted with different conditions presented various properties. Pectin extracted at pH 2.5 had higher esterification degree (DE, ~40%) and gelled at 3% (w/v) concentration. In contrast, pectin extracted under mild condition with low DE (21%) cannot gel at the same concentration. Conclusively, superfine grinding has potential application in pectin extraction.