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

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”