Effect of heat treatment and pH on the thermal, surface, and rheological properties of Lupinus albus protein

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% (wt/vol). The suspensions were treated at 75, 90, or 100°C for 1 h. The heat-treated protein was characterized by SDS-PA...

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Bibliographic Details
Published in:Journal of the American Oil Chemists' Society 2005-02, Vol.82 (2), p.135-140
Main Authors: Mohamed, A, Peterson, S.C, Hojilla-Evangelista, M.P, Sessa, D.J, Rayas-Duarte, P, Biresaw, G
Format: Article
Language:English
Subjects:
Biological and medical sciences
buffers
DSC
Fat industries
Flowers & plants
Food industries
Fundamental and applied biological sciences. Psychology
Heat treatment
hydrophobicity
interface phenomena
interfacial tension
legumes
lupin meal
Lupinus albus
Meals
meals (products)
Moisture content
physicochemical properties
plant proteins
Proteins
rheological properties
Rheology
seeds
surface hydrophobicity
Surface tension
Temperature
thermal properties
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Summary: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% (wt/vol). The suspensions were treated at 75, 90, or 100°C for 1 h. The heat-treated protein was characterized by SDS-PAGE, free zone capillary electrophoresis (FZCE), and DSC; and its surface hydrophobicity, surface tension, and rheological properties were examined. The presence of high M.W. aggregates was apparent from SDS-PAGE and FZCE results. Solubility was lowest at pH 4 and 100°C. DSC analysis was performed on low moisture content samples (3.1%) and 20% (wt/vol) suspensions. DSC analysis at 3.1% moisture content showed a glass transition around 85°C and an exothermic transition at 160°C, whereas the protein suspension showed a more thermally stable protein as indicated by the higher ΔH 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 90°C 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 (100°C) and pH 6.8.
ISSN:0003-021X
1558-9331
DOI:10.1007/s11746-005-1055-8