Analysis of Soybean Protein- Derived Peptides and the Effect of Cultivar, Environmental Conditions, and Processing on Lunasin Concentration in Soybean and Soy Products

Authors: WANG, WENYI - UNIV OF ILLINOIS; DIA, VERMONT - UNIV OF ILLINOIS; VASCONEZ, MIGUEL - UNIV OF ILLINOIS; Nelson, Randall; DE MEJIA, ELVIRA - UNIV OF ILLINOIS

Submitted to: Journal of Association of Official Analytical Chemists International
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/2/2008
Publication Date: 8/20/2008
Citation: Wang, W., Dia, V.P., Vasconez, M., Nelson, R.L., De Mejia, E.G. 2008. Analysis of Soybean Protein- Derived Peptides and the Effect of Cultivar, Environmental Conditions, and Processing on Lunasin Concentration in Soybean and Soy Products. Journal of Association of Official Analytical Chemists International. 91:936-946.

Interpretive Summary: Soybean is an important source of proteins for human foods. There is increasing interest in soybean protein because of its reported health benefits. These health benefits are attributed to a variety of components of soybean protein. Lunasin is one of those components that is reported to arrest cell division in cancer cells. This article provides a comprehensive review of the methods used in the analysis of these components with a special emphasis on techniques used to measure lunasin and the factors that can affect lunasin concentration. There are a wide variety of techniques available that can be used to identify the various components of soybean protein and it is important to choose the method most appropriate for the specific research objectives. Lunasin concentration in soybean protein is affected by both the soybean variety and the environmental conditions in which that variety is grown. High temperatures during the later stages of seed development reduces lunasin concentration. Lunasin concentrations can be increased by breeding and by selecting appropriate environments in which to grow the soybeans. These results will be of interest to scientists studying bioactive compounds of soybean protein and those that would like to increase the concentration of lunasin.

Technical Abstract: Soybean, an important source of food proteins, has received increasing interest from the public because of its reported health benefits. These health benefits are attributed to its components including isoflavones, saponins, proteins and peptides. Lunasin, Bowman-Birk inhibitor, lectin, and ß-conglycinin are some of the biologically active peptides and proteins found in soybean. This article provides a comprehensive review on the recently used techniques in the analysis and characterization of food bioactive peptides with emphasis on soybean peptides. The methods used to isolate and purify lunasin from defatted soybean flour were ion-exchange chromatography, ultrafiltration and gel filtration chromatography. The identity of lunasin was established by SDS-PAGE, Western blot, MALDI-TOF and LC/MS-MS. The results on the effect of soybean cultivar and environmental factors on lunasin concentration are also reported. The highest lunasin concentration, 11.7 ± 0.3 mg/g flour, was found in Loda soybean cultivar grown at 23°C; while the lowest concentration, 5.4 ± 0.4 mg/g flour, was found in Imari soybean cultivar grown at 28°C. Lunasin concentration was affected by cultivar-temperature, cultivar-soil moisture and cultivar-temperature-soil moisture interactions. The variation on lunasin concentration suggests that its content can be improved by breeding, and by optimization of growing conditions. In summary, bioactive peptides can be accurately identified and quantified using different techniques and conditions. In addition, lunasin concentration in soybean depends mainly on cultivar and to some extent on environmental factors particularly temperature. Lunasin concentration in soy products was also affected by processing conditions.