Submitted to: Lupin International Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: June 24, 2002
Publication Date: N/A
Interpretive Summary: The main objective of this work is to develop new uses for alternate 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 lack of information and basic research on lupin proteins and other major components. A 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 National Center for Agricultural Utilization Research participated by developing procedures to characterize and compare lupin proteins to more popular legumes. This project was focused in determining thermal and rheological properties of lupin flour meal. Utilization of lupin flour in baked and pasta products can also be considered to increase the nutritional value of these products. The use of lupin in the snack industry can be explored by developing different extruded snacks. Lupin protein's structure-function was also explored to increase chances for use in different types of foods (i.e., foaming properties, gel strength, heat stability) and interactions with other food components. Basic physical, mechanical and rheological properties and performances of lupin proteins and oils were performed to provide information and direction for end-use food and non-food applications.
Technical Abstract: Research on the structure and function relationships of lupin meal or lupin native protein is limited. 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. Untreated sample was used as a control. The treated samples solids were freeze-dried and later used for MDSC analysis at low moisture (3.1%) and 20% slurry. The DSC data showed a glass and exothermic transitions for all samples regardless of the kind or the level of treatment. The exothermic reaction is indicative of lupin protein aggregation when heated in a meal form. At low moisture and 90 deg C lupin proteins showed higher glass transition energy values 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 aggregation 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 of structure and property relationship. 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 did not relax an order of magnitude within a thousand seconds indicating that the molecules of lupin might be, somehow, cross-linked. To some extent, our studies of lupin defatted meal suspensions demonstrated that lupin exhibited some wheat gluten viscoelastic properties.