RESUMO
The impact of pH (6-9) and NaCl concentration (0-0.5 mol.L-1) on sunflower protein extraction was studied through design of experiments. The considered criteria were protein extraction yield (total proteins, helianthinin and albumins), chlorogenic acids covalently bound to proteins, and free chlorogenic acid concentration in the aqueous extract. Statistical analysis showed that the obtained by design of experiments the polynomial models of each extraction criteria were reliable for predicting the responses. They were employed in an original multi-objective optimization methodology. The optimal conditions revealed to be pH 7.3/0.3 mol.L-1 NaCl yielded 46.83% and 59.16% of total protein and albumin extraction yield, 1.730 and 1.998 mg.g-1 of chlorogenic acids covalently bound to helianthinin and albumins in aqueous extract, respectively. The sunflower protein isolate obtained after extraction in this condition had good solubility (40-80% at pH 5-8), functional properties (foaming and emulsifying) and a satisfying color.
Assuntos
Helianthus/metabolismo , Extração Líquido-Líquido/métodos , Proteínas de Plantas/isolamento & purificação , Extração em Fase Sólida/métodos , Albuminas/análise , Albuminas/isolamento & purificação , Albuminas/metabolismo , Ácido Clorogênico/química , Ácido Clorogênico/metabolismo , Concentração de Íons de Hidrogênio , Isomerismo , Extração Líquido-Líquido/instrumentação , Proteínas de Plantas/análise , Proteínas de Plantas/metabolismo , Polifenóis/análise , Polifenóis/metabolismo , Ligação Proteica , Cloreto de Sódio/química , Extração em Fase Sólida/instrumentaçãoRESUMO
The method described in the article aims at the quantification of both main storage proteins, globulins and albumins, in aqueous extract from rapeseed, as an alternative to the current reference methods, Kjeldahl and SDS-PAGE electrophoresis. The new method lies on the analytical separation of extracted compounds by Size-Exclusion High Performance Liquid Chromatography (SE-HPLC) (Biosep-SEC-s2000, 5⯵m). The elution of rapeseed extracts with water/acetonitrile/trifluoroacetic acid (45/55/0.1% v/v) during 30â¯min yields two distinct peaks for the main proteins of rapeseed. Based on the protein extinction coefficients, a calibrationless methodology was developed for their quantification on the basis of the UV signal. The SE-HPLC method was successfully compared to references: Kjeldahl and SDS-PAGE densitometry for the determination of the proportion of each protein. Then, it was successfully applied on two other oleoproteagineous plants, linseed and sunflower.
