Solubilization and Electrophoretic Characterization of Select Edible Nut Seed Proteins

Abstract

The solubility of almond, Brazil nut, cashew nut, hazelnut, macadamia, pecan, pine nut, pistachio, walnut, and peanut proteins in several aqueous solvents was qualitatively and quantitatively assessed. In addition, the effects of extraction time and ionic strength on protein solubility were also investigated. Electrophoresis and protein determination (Lowry, Bradford, and micro-Kjeldahl) methods were used for qualitative and quantitative assessment of proteins, respectively. Depending on the seed, buffer type and ionic strength significantly affected protein solubility. The results suggest that buffered sodium borate (BSB; 0.1 M H(3)BO(3), 0.025 M Na(2)B(4)O(7), 0.075 M NaCl, pH 8.45) optimally solubilizes nut seed proteins. Qualitative differences in seed protein electrophoretic profiles were revealed. For a specific seed type, these differences were dependent on the solvent(s) used to solubilize the seed proteins. SDS-PAGE results suggest the polypeptide molecular mass range for the tree nut seed proteins to be 3-100 kDa. The results of native IEF suggested that the proteins were mainly acidic, with a pI range from >4.5 to <7.0. Western immunoblotting experiments indicated that rabbit polyclonal antibodies recognized substantially the same polypeptides as those recognized by the corresponding pooled patient sera IgE.

Bioactive, functional and edible film-forming properties of isolated hazelnut (Corylus avellana L.) meal proteins

“…These authors solubilized nut proteins from defatted nut flour and then investigated their SDS-PAGE profiles without applying isoelectric precipitation of proteins. There were some differences in the band intensities and profiles obtained by these authors and those obtained by the current study for hazelnut proteins, but concentration of most intensive protein bands determined by Sathe et al (2009) between 20 and 30 kDa (close to 20 kDa) compared well with the results of current study.…”

“…Moreover, these authors did not determine any minor hazelnut protein fractions between pI 7.0 and 8.5. However, it is hard to understand the reasons of differences between results of Sathe et al (2009) and the current work which uses different material (defatted and acetone treated meal) and different methods for extraction, purification and isoelectric focusing of protein. On the other hand, the MW pattern of HPI-AW proteins obtained by a Different letters in each column show significant differences at P < 0.05. the 2D electrophoresis was quite similar with that obtained with the classical SDS-PAGE.…”

“…However, it seems that the significant differences in bioactivity, functionality and film making properties of protein extracts are not due to major differences in MW of their monomeric fractions but due to differences in their conformations caused by the acetone washing and/or hot extraction. The SDS-PAGE of different nut proteins including hazelnut proteins has been previously studied by Sathe et al (2009) with details. These authors solubilized nut proteins from defatted nut flour and then investigated their SDS-PAGE profiles without applying isoelectric precipitation of proteins.…”

“…The majority of the high MW proteins had pI between 5.0 and 5.4, while low MW fractions concentrated between pI 7.0 and 8.5. Sathe et al (2009) applied isoelectric focusing of hazelnut proteins extracted from defatted flour with TriseHCl buffer at pH 8.1 found that these proteins migrated mainly around pI 5.85 (between pI > 5.2 and pI < 6.55). Moreover, these authors did not determine any minor hazelnut protein fractions between pI 7.0 and 8.5.…”

Allergenicity attributes of different peanut market types

“…The samples extracted 1:10 (w/v) should have contained a theoretical concentration of 25 mg/mL if all of the protein in the kernel was solubilized and subsequently extracted. Sathe et al also found that extractable protein for peanut as determined by the Bradford method was somewhat lower that the theoretically expected value based on the nitrogen content of peanut kernels (Sathe et al, 2009). This can be due to incomplete extraction (Leco analysis measures the nitrogen content in the solid material of peanut, independent on extractability or solubility of different proteins), or because the two methods are calibrated by different means.…”