Submitted to: Lupin International Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: June 24, 2002
Publication Date: June 24, 2002
Citation: MOHAMED, A., XU, J. THERMAL AND RHEOLOGICAL PROPERTIES OF LUPINUS ALBUS FLOUR MEAL. PROCEEDINGS OF LUPIN INTERNATIONAL CONFERENCE.2002.P.24-28. Technical Abstract: There is very little research done in the area of structure and function relationships of lupin meal or lupin native protein. The scope of this work is to study lupin's native proteins thermal and rheological properties in whole meal. The effect of pH and heat treatment on the thermal properties of lupin meal was studied. Lupinus Albus grain was hand dissected and the separated endosperm was milled to flour meal. Suspension (20%) was prepared with three phosphate buffers (pH 4, 6.8, and 8) and heat treated at 75 and 90 deg C for 1 hr. The treated samples were freeze-dried and later used for MDSC analysis at low moisture (3.2%) and 20% slurry. The DSC data produced a glass and exothermic transitions for all samples regardless of the kind or the level of treatment. The exothermic reaction indicates lupin protein aggregate when heated in a meal form. At low moisture and 90 deg C lupin proteins showed higher glass transition energy requirements and higher temperatures while the exothermic transition showed lower temperatures and delta H when compared to the control. Proteins solubility increased at higher pH values. At pH 4, the temperatures and denaturation energy values were lower when compared to pH 8, indicating protein stability at higher pH versus lower pH values. Defatted untreated flour meal was used for rheological study. By measuring the linear rheological properties of a series of concentrations of defatted lupin meal suspensions, we obtained some insight into the structure and property relationships. Defatted lupin suspensions exhibited strong viscoelastic solid properties, which were similar to those of wheat gluten. Both storage (G') and loss (G") moduli increased dramatically over a narrow range of lupin meal concentrations. But the linear range of the rheological properties of lupin was very small. Stress relaxation studies showed that lupin suspensions relaxed within a short time indicating the lack of crosslinking in the lupin system.