Among three varieties of Australian lentils, Len culinaris, Matilda had larger physical dimensions and higher protein contents, but no significant difference in chemical composition or physical dimensions existed between Digger and Cobber. Optimum conditions for the extraction of lentil flours which passed through a 0.79 mm screen were pH 9.0 at 30??C for Matilda and pH 8.5 at 35??C for both Digger and Cobber. These conditions enable a high yield of lentil starches and proteins, with minimal changes or damage to their quality. Matilda offered advantages for processors over the other varieties: it had higher protein and fibre; lower lipid; and greater foam-forming capacity and foam stability. Its starch had higher Tg, lower Tm and better expansion behaviour. All lentil starches were shear-thinning. The flow of the molten lentil starches under limited moisture content differed from starches sheared in excess moisture condition. When extruded, lentil starches offered good expansion and had higher Tg than did cereal starches in extruded products. The overall rheological behaviour of lentil flours differed from that of their corresponding starches. The lentil flours had poorer pasting quality and expansion possibly because of interference by their lipid and protein components. Starch rheological behaviour was greatly affected by the amylose/amylopectin ratio and the molecular weight of starches, while flour behaviour was more influenced by the interfering components. The ?? value obtained from capillary rheometry (CR) could be used for the screening of materials for their expansion behaviour. The CR data gave excellent agreement to the results achieved from the extruder and in predicting the expansion indices and calculated viscosity of six flour blends. In all, the quantitative and qualitative knowledge on the physico-chemistry and rheology of lentils give a better understanding of the behaviour of lentil flours and starches in the expansion of extruded products, producing suitable end products with acceptable quality and storage stability. This project highlights the lentil flour and starch rheology characteristics in view of possible application in extruded products.
| Identifer | oai:union.ndltd.org:ADTP/257636 |
| Date | January 2007 |
| Creators | Lee, Huang Chun, Chemical Sciences & Engineering, Faculty of Engineering, UNSW |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | http://unsworks.unsw.edu.au/copyright, http://unsworks.unsw.edu.au/copyright |
Page generated in 0.0017 seconds