Physicochemical and structural characterisation of protein isolate, globulin and albumin from soapnut seeds (Sapindus mukorossi Gaertn.)

Shou-Wei Yin; Ji-Cheng Chen; Shang-De Sun; Chuan-He Tang; Xiao-Quan Yang; Qi-Biao Wen; Jun-Ru Qi

doi:10.1016/j.foodchem.2011.03.046

Physicochemical and structural characterisation of protein isolate, globulin and albumin from soapnut seeds (Sapindus mukorossi Gaertn.)

Food Chem. 2011 Sep 15;128(2):420-6. doi: 10.1016/j.foodchem.2011.03.046. Epub 2011 Mar 12.

Authors

Shou-Wei Yin¹, Ji-Cheng Chen², Shang-De Sun³, Chuan-He Tang⁴, Xiao-Quan Yang⁴, Qi-Biao Wen⁴, Jun-Ru Qi⁴

Affiliations

¹ Department of Food Science and Technology, South China University of Technology, Guangzhou 510640, PR China; State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou 510640, PR China. Electronic address: feysw@scut.edu.cn.
² Institute of Plant Protection and Microbiology, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, PR China; Department of Food Science and Nutrition, Zhejiang University, Hangzhou 310029, PR China.
³ Lipid Technology and Engineering, School of Food Science and Engineering, Henan University of Technology, 140 Songshan South Road, 4, Zhengzhou 50052, PR China.
⁴ Department of Food Science and Technology, South China University of Technology, Guangzhou 510640, PR China.

PMID: 25212151
DOI: 10.1016/j.foodchem.2011.03.046

Abstract

The amino acid (AA) composition and physicochemical and conformational properties of protein isolate (SNPI), globulin (SNG) and albumin (SNA) fractions from soapnut seeds were evaluated. The essential AA of SNG, SNA and SNPI (except sulfur-containing AA) are sufficient for the FAO/WHO suggested requirements for 2-5year old infants. SNG and SNPI showed similar electrophoresis patterns and AA compositions, the subunit of those proteins consisted of two polypeptides linked by disulfide bonds. In contrast, SNA showed a different AA compositions and SDS-PAGE pattern. Both SNG and SNPI presented a typical U-shape protein solubility (PS)-pH profile, SNA showed a completely different PS-pH profile, especially at pH 2.0-4.0. The near-UV circular dichroism (CD), differential scanning calorimetry (DSC) and tryptophan fluorescence spectra analyses indicated that the flexibility in tertiary conformations decreased in the order: SNA>SNPI>SNG, while soapnut proteins had a similar secondary conformation, with a highly ordered structure (the β-types), as evidenced by far-UV CD spectra.

Keywords: Albumin; Conformation; Globulin; Physico-chemical property; Protein isolate; Soapnut (Sapindus mukorossi Gaertn.).