Isoelectric protein precipitation from mild-acidic extracts of de-oiled sunflower (<Emphasis Type="Italic">Helianthus annuus</Emphasis> L.) press cake |
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Authors: | Claudia Pickardt Thomas Hager Peter Eisner Reinhold Carle Dietmar R Kammerer |
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Affiliation: | (1) Institute of Food Science and Biotechnology, Chair Plant Foodstuff Technology, Hohenheim University (150d), Garbenstrasse 25, 70599 Stuttgart, Germany;(2) Fraunhofer Institute for Process Engineering and Packaging (IVV), Giggenhauser Strasse 35, 85354 Freising, Germany; |
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Abstract: | Sunflower protein extraction using sodium chloride solutions allows high extraction yields at pH ~6 while preventing oxidation
and covalent binding of phenolic compounds to the proteins, which usually occurs under alkaline conditions. Since protein
solubility is enhanced at high NaCl concentrations, isoelectric precipitation had to be adapted in the present study besides
developing subsequent desalting steps. Precipitation losses decreased from 62 to 31% with increasing NaCl (0.6–2.0 mol/L)
and protein concentrations of the solution (6–14 mg/mL) and decreasing pH of precipitation (pH 4.5–3.0). Maximum yields were
achieved at low temperature (8 °C) and upon instant acid addition. After adsorptive removal of co-extracted phenolics from
the protein extracts, overall protein yields were considerably higher after precipitation at pH 3.5 compared with 4.5, but
only slightly higher after washing of the precipitates. The physico-chemical properties of the protein isolates did not differ
significantly except for the marked protein denaturation upon precipitation at pH 3.5. From the proposed process, light-coloured
protein isolates of high purity (>98%) are obtained, which are suitable for food use. |
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