Extraction Of Sunflower Head Pectin And Its Application In Macrocapsule

Sunflower head is a byproduct of sunflower seed oil producing process. It contains 15%~25%(w/w) low methoxyl pectin(LMP). So far, acid method with chelators such as hexametaphosphate or ammonium oxalate is the mainly way to extract pectin from sunflower head. The extract is subsequently treated with alcohol, whereby pectin precipitates can be developed and later isolated by filtration. The pectin extracted by hexametaphosphate has a low quality.Ammonium oxalate will result in food security risk. Alcohol treatment is fast and ready-to-operate, however, sewage discharge and alcohol recycle are problems in scale-up production. In the present paper, focus is emphasized on the conditions of the extract with sodium citrate, and the extract was purified by ultrafiltration aiming to develop a clean and safe method. Preparation of the pectin-Whey Isolate Protein(WPI) compounds used the extract pectin and WPI, and the properties of the compounds were studied.Firstly, based on single factor experiments, the optimal extract conditions were as follows: After pretreatment, the sunflower head powders was subjected to extraction which was performed using 0.6%(w/v) sodium citrate solution at 85℃, p H 2.50 for 3.5 h with solid-to-liquid ratio(SLR) of 1:40(w/v), and the galacturonic acid content was 16.90%(w/w). The membrane used in the ultrafiltration with a surface of 1.77m2 and a molecular weight cut-off of 8000 Da to purified the extract until the conductivity of the retentate below 2500 μs/cm. After ultrafiltration, the salt residue in retentate were further adsorbed by using a strong-basic anion-exchange resin(717) and a strong-acidic cation-exchange resin(732).The final conductivity was less than 400 μs/cm. Finaly, pectin powders was subsequently obtained by spray-drying.Secondly, the extract pectin was characterized. The DM and the DA of the pectin were 22.56% and 3.42%, separately. The Mw was 256.4 k Da and the Mn was 56.3 k Da which were lower than the pectin extracted by ammonium oxalate. This proved that the extracted pectin had a deeper degradation. The main monosaccharide unit constituting the extracted pectin was Gal A(49.4%), followed by rhamnose(14.9%) and galactose(11.4%). The high value of RG-? region might be the result of ultrafiltration. During ultrafiltration, the HG and RG fragments with MW>8000 Da were remained in retentate and small fragments were removed with permeation. In the case of alcohol treatment(50%~70%, v/v), big fragments could be precipitated out and small HG and RG fragments still dissolve in aqueous. The shape of pectin was spheroid with slight shrinkage. Pectin powders had the size range of 2 μm~5 μm. As a result, the product could rapidly dissolve in water at ambient temperature. The mechanism of the aggregation of pectin in aqueous with different concentration was studied. With the increase of pectin concentration, the flexible filaments became stronger and rigid.Finally, different ratio(LMP:WPI=2:1, 3:2, 1:1, 2:3, 1:2,(w/w)) of LMP-WPI compounds were prepared. The properties of LMP-WPI compounds as wall material in macrocapsule with the core of β-carotene(dissolved in edible oil) were studied. When LMP:WPI=3:2, the volum of the contained oil reached a maximum value(18 m L/g). The macrocapsules had the size range of 1 μm~5 μm. The macrocapsules could disperse in water rapidly but were destroyed in n-hexane. The macrocapsules gathered in the disperse aqueous under 85℃ for 1 h and some free oil could be observed when heating for 3 h. The disperse solution was stable in p H 5.0~7.0 at ambient temperature but unstable in p H 3.0~4.0 and p H 8.0~10.0. In p H 3.0~4.0, the disperse solution had a deeper destruction.