|Rayas-Duarte, Patricia - OKLAHOMA STATE UNIV|
Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 7, 2005
Publication Date: April 1, 2005
Citation: Mohamed, A., Peterson, S.C., Hojillaevangelist, M.P., Sessa, D.J., Rayas-Duarte, P., Biresaw, G. 2005. The effect of heat treatment and pH on the thermal, surface, and rheological properties of Lupinus albus protein. Journal of the American Oil Chemists' Society. 82(2):135-140. Interpretive Summary: The main objective of this work is to develop new uses for alternative crops. Lupin is a legume with high protein and oil content. Lupin utilization in the U.S. food and feed industry is not fully explored, partially due to the lack of information and basic research on lupin proteins and other major components. Comprehensive product development for the food and feed industry is needed using lupin flour to attract investors. To complement agronomist effort, the protein group of the Cereal Products and Food Science Unit of the NCAUR participated by characterizing lupin proteins and comparing their properties with those of other legumes. This project was focused on determining thermal and rheological properties of lupin flour meal. Utilization of lupin flour in baked goods and pasta products improves their nutritional value. Structure-function relationships of the lupin proteins (i.e. foaming properties, gel strength, heat stability and interactions with other food components) were also explored to investigate opportunities for their use in different types of food and non-food applications. Since lupin is high in protein while having no starch, there is future potential as a low-carbohydrate food source.
Technical Abstract: Endosperm from hand dissected and dehulled Lupinus albus seeds was milled into meal, sieved through a 40 mesh screen, and suspended in phosphate buffers (pH 4, 6.8, and 8) at 20% (w/v). The suspensions were treated at 75, 90 or 100ºC for one hour. The heat-treated protein was characterized by SDS-PAGE, free zone capillary electrophoresis, and DSC, and its surface hydrophobicity, surface tension, and rheological properties were examined. The presence of high M.W. aggregates were apparent from SDS-PAGE and free zone capillary electrophoresis results. Solubility was the lowest at pH 4 and 100ºC. DSC analysis was performed on low moisture content samples (3.1%) and 20% (w/v) suspensions. DSC analysis at 3.1% moisture content showed a glass transition around 85ºC and an exothermic transition at 160ºC, while the protein suspension showed a more thermally stable protein as indicated by the higher delta-H values. Lupin protein was surface active as demonstrated by its effectiveness in reducing the surface tension of the aqueous phosphate buffer. Surface hydrophobicity of the heat-treated protein decreased as the treatment temperature increased, which supports the SDS-PAGE results. The highest level of aggregation was noted at 90ºC and pH 6.8 as indicated by low surface hydrophobicity values. Rheological studies showed direct relationships between the shear storage modulus (G') of the lupin meal suspension and both pH and temperature treatment, although this effect is minimal at the highest temperature (100ºC) and pH 6.8.