ARS | Publication request: Functional Properties of Soybean and Lupin Protein Concentrates Produced by Ultrafiltration-Diafiltration

Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 9, 2004
Publication Date: December 1, 2004
Citation: Hojillaevangelist, M.P., Sessa, D.J., Mohamed, A. 2004. Functional properties of soybean and lupin protein concentrates produced by ultrafiltration-diafiltration. Journal of the American Oil Chemists' Society. 81(12):153-1157

Interpretive Summary: Extrusion-expelling (E-E) is a simple, inexpensive, and solvent-free process that is rapidly gaining popularity in the oilseed industry. The meal from E-E is believed to have good functional properties owing to less severe conditions in the process, and, therefore, can be used as the starting materials for the production of the higher-value flours, protein concentrates or protein isolates. There is very limited research on the production of soy flours from E-E meal. There has been no investigation yet on the preparation and quality of concentrates or isolates from E-E meal. Our research explored ultrafiltration (UF) followed by diafiltration (DF, a method of de-salting) as a means of producing protein concentrates or isolates from E-E soybean meal, as well as, from lupin seeds. Lupin (genus Lupinus) is a legume that has a composition similar to that of soybeans, making it a good source of oil and protein for human and animal consumption. It thrives in areas where soybeans can not grow, and tolerates frost, drought and poor soil. Despite these attractive qualities, lupin has had limited utilization because of its alkaloid levels and low agronomic yield. Breeding programs, however, have now overcome these problems and there is renewed interest in developing lupin as a protein or fiber source. Our study then was conducted to determine the effects of UF-DF on functional properties of extracted proteins from E-E soybean meal and undefatted lupin (Lupinus albus L.2043N) meal and compare the results with those of proteins prepared by conventional acid-precipitation. We found that UF-DF produced only protein concentrates (at least 70% crude protein content), while acid-precipitation produced protein isolates (at least 90% crude proteint). We found that soy protein concentrate produced by UF-DF showed improved functional properties, such as solubilities up to pH 7.0, surface hydrophobicity, emulsifying capacity, foaming capacity and heat stability. With lupin proteins, UF-DF did not produce a comparable improvement in their functional properties as it did for soybean protein. Our results showed that it is technically feasible to produce soy protein concentrates from E-E meal by using UF-DF. The concentrates possess functional properties that are useful for a variety of both food and non-food applications. Production of protein concentrates from E-E soy meal may help boost the utilization of E-E, a more environmentally-safe process for oil extraction, and will certainly add value to soybeans, thus potentially generating additional income to soybean farmers.

Technical Abstract: Ultrafiltration followed by diafiltration (UF-DF) was evaluated for the production of protein products from partially defatted soybean meal or undefatted lupin (Lupinus albus L.2043N) meal. This study determined the effects of UF-DF on functional properties of the extracted proteins and compared the result with those of protein prepared by acid-precipitation (AP). UF-DF produced only protein concentrates (73% crude protein, dry basis, db), while AP produced protein isolates (about 90% crude protein, db). Soybean protein produced by UF-DF showed markedly higher values for solubilities up to pH 7.0, surface hydrophobicity index, emulsion activity index and foaming capacity than did the acid-precipitated soybean protein. UF-DF soy protein was also the most heat-stable among all protein samples tested. With lupin proteins, only emulsion activity index was significantly improved by using UF-DF. UF-DF generally had no adverse effects on, and in most cases even improved, the functional properties of soy protein concentrate produced by this method. UF-DF did not produce a comparable improvement in functional properties of lupin proteins as it did for soybean protein.