Th3_Molecular features of protein and starch in African rice relate to their processing behavior

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3rd Africa Rice Congress …

3rd Africa Rice Congress
Theme 3: Rice processing and marketing
Mini symposium: Adding value to Africa’s rice: rice-derived products
Author: Barbiroli

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  • 1. Molecular features of protein and starch in African rice relate to their processing behavior Stefania Iametti Alberto Barbiroli, Francesco Bonomi, Alessandra Marti, Mauro Marengo, Maria Ambrogina Pagani, John Manful# DeFENS, University of Milan, Italy # Africa Rice, Benin
  • 2. The targets To investigate the properties of starch and protein in rice varieties popularly cultivated in Africa To identify which varieties/species could be most suitable for developing various specific food products Structural and physical properties of starch and proteins were studied by using a multidisciplinary approach
  • 3. STRUCTURAL CHARACTERIZATION OF PROTEINS Nature & abundance: - SDS-PAGE Structural organization: - Solubility (also in denaturing/dissociating media) Reactivity: - Exposure of possible reticulating moieties: thiols (-SH)
  • 4. STRUCTURAL CHARACTERIZATION OF PROTEINS Nature & abundance: - SDS-PAGE Highlights species-specific differences O. sativa O. glaberrima
  • 5. STRUCTURAL CHARACTERIZATION OF PROTEINS Nature & abundance: - SDS-PAGE (O. sativa) Highlights variety-specific differences A B C D E F
  • 6. STRUCTURAL CHARACTERIZATION OF PROTEINS Structural organization: - Solubility (also in denaturing/dissociating media) 60 50 protein, mg/g rice Highlights species-related differences, and also differences related to agronomical issues protein solubility in the presence/absence of dissociating and reducing agents 40 30 sativa 1 sativa 2 sativa 3 glaberrima 20 10 0 buffer only + urea + urea & DTT
  • 7. STRUCTURAL CHARACTERIZATION OF PROTEINS Reactivity: - Exposure of possible reticulating moieties (-SH) 1.4 conditional accessibility of protein thiols 1.2 micromol -SH/g rice Highlights species-related differences, but also differences related to agronomical issues (in particular when considering their relative protein content) 1.0 0.8 sativa 1 sativa 2 sativa 3 glaberrima 0.6 0.4 0.2 0.0 buffer + urea
  • 8. STRUCTURAL CHARACTERIZATION OF STARCH Structural organization: - susceptibility to selective enzymatic activities Pasting behaviour - MVAG Brabender Interaction with water in complex/competing systems: - TGA & DSC
  • 9. STRUCTURAL CHARACTERIZATION OF STARCH Structural organization: - susceptibility to selective enzymatic activities Pasting behaviour - MVAG Brabender Interaction with water in complex/competing systems: - TGA &DSC
  • 10. STRUCTURAL CHARACTERIZATION OF STARCH Structural organization: as detected by susceptibility to selective enzymatic activities, followed by GPC/MALS GLAB 766 NERICA Starch degradation by endogenous enzymes results in a different pattern of breakdown products in different rice samples WITA8 The effects of purified pullulanase highlight a different sensitivity of starch components in each variety/species towards debranching WITA8 GLAB 766 NERICA
  • 11. STRUCTURAL CHARACTERIZATION OF STARCH Pasting behaviour - MVAG Glaberrima 766 Sativa 1 Sativa 4 Sativa 3 Sativa 5 Temperatura (°C) 1200 100 80 800 sativa 60 600 40 400 20 200 glaberrima 0 0 0 5 10 15 20 25 30 35 Time (min) 40 45 50 55 60 65 Temperature (°C) Viscosity (B.U.) 1000
  • 12. CONCLUDING REMARKS The approaches presented here seem able to provide useful insights as for the structural characteristics of starch and proteins in various African rice varieties Further studies will have to verify whether the “molecular-based” information we are gathering will be able to define proper processing and the possible end uses of some of the materials investigated here
  • 13. PEOPLE THAT MADE IT POSSIBLE Students & post-docs DeFENS Prof. Dimitrios Fessas DeFENS Partners & Funding from GRISP project “New Products”