Pistachio Hull As an Alternative Pectin Source: Its Extraction and Use in Oil in Water Emulsion System.

In this study, pectin was extracted from the pistachio hull using two methods: conventional extraction and ultrasound-assisted extraction. Water and citric acid solution were tested separately as extraction solvents in both conventional and ultrasound methods. The highest yield (32.3 +/- 1.44%) was obtained using a citric acid solution in the conventional extraction method. The pectin extracted with this method had 38.94 g acid per 100 g dry pectin extract. The galacturonic acid and ash contents were 65.81 +/- 1.51 and 1.57 +/- 0.03%, respectively. The pistachio hull pectin was under the low methoxy pectin group with a 19.29 +/- 0.41% degree of esterification. The emulsifying property of the pectin extracted was investigated in an oil-in-water emulsion system at six different pectin concentrations (2, 4, 5, 6, 8, and 10% w/w) and at a fixed oil ratio (20% w/w). Emulsion performance was investigated in terms of emulsion stability, microstructural characteristics, droplet size, and rheological properties. The most stable emulsion was obtained at a 6% pectin concentration. The emulsifying activity index, emulsion stability index, droplet size, consistency index, and flow behavior index were 172.85 +/- 0.59 m(2)/g, 158.28 +/- 3.41 min, 6.08 +/- 0.04 mu m, 0.72 +/- 0.001 Pa center dot s(n), and 0.752 +/- 0.005 at this concentration, respectively.