EFFECTS OF SOAKING AND
STEAMING REGIMES ON THE
QUALITY OF ARTISANAL PARBOILED
RICE
Manful J.T
Graham-Acquaah, S*
Tchatcha,...
Introduction
Parboiling rice
involves partially boiling rice in its husk

It is done to
– seal internal fissures in the ...
How it’s done
Industrial parboiling

Artisanal parboiling

1. Soaking

1. Soaking

 Constant temperature
(60 -65ºC)
 For...
Artisanal parboiling
Improving artisanal parboiling is a key component of
many rice improvement programs in Africa
Soaki...
Objective
To characterize the effects of initial soaking
temperature and steaming time on some
physicochemical properties ...
Methods
Experimental design
• Central Rotatable Composite Design (CRCD)
– 2 factors namely
• soaking temperature: 30-90ᵒC
...
Methods

Plate 1: Soaking process
(300g/900ml water)

Plate 2: Steaming process
Results
Table 1: Effect of treatment combinations on some quality indices
Total milled
Cooking
Treatment
rice yield (%) ti...
Estimated Response Surface
Raw rice HRY = 36.3%
Regression
Coefficient
23.40

X0(Constant)

X1(Soak temp)
X2(Steam time)

...
Estimated Response Surface

Regression
Coefficient
4.48

X1(Soak temp)

-0.05***

X2(Steam time)

0.15

Term

X12

0.21×10...
5000

90ᵒC/20min
4000

60ᵒC/1.9mins
60ᵒC/23mins

3000

2000

1000

0
8
56
104
152
200
248
296
344
392
440
488
536
584
632
...
Estimated Response Surface
Raw rice peak viscosity = 2565cP
Term

X0(Constant)

1183.69
7.69***

X1(Soak temp)
X2(Steam ti...
Chalkiness ≤ 2.0

HRY ≥ 60%

Steaming time

Optimal region

20

15

10

5

20

30

40
50
60
70
80
Soaking temperature

90
...
Table 5: Validation of results from response surface optimization

Validation
run

Soaking
temp (°C)

Steaming
time (mins)...
Conclusions
To parboil to achieve good head rice yield and low chalkiness:
 Optimal range for initial soaking temperature...
Th3_EFFECTS OF SOAKING AND STEAMING REGIMES ON THE QUALITY OF ARTISANAL PARBOILED RICE
Upcoming SlideShare
Loading in …5
×

Th3_EFFECTS OF SOAKING AND STEAMING REGIMES ON THE QUALITY OF ARTISANAL PARBOILED RICE

766 views

Published on

3rd Africa Rice Congress
Theme 3: Rice processing and marketing
Mini symposium:Improving the quality of rice produced in Africa
Author: Graham-Acquaah

Published in: Technology, Business
0 Comments
2 Likes
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total views
766
On SlideShare
0
From Embeds
0
Number of Embeds
10
Actions
Shares
0
Downloads
16
Comments
0
Likes
2
Embeds 0
No embeds

No notes for slide

Th3_EFFECTS OF SOAKING AND STEAMING REGIMES ON THE QUALITY OF ARTISANAL PARBOILED RICE

  1. 1. EFFECTS OF SOAKING AND STEAMING REGIMES ON THE QUALITY OF ARTISANAL PARBOILED RICE Manful J.T Graham-Acquaah, S* Tchatcha, D
  2. 2. Introduction Parboiling rice involves partially boiling rice in its husk It is done to – seal internal fissures in the grain and obtain higher head rice yields during milling – enhance the nutritional value of rice
  3. 3. How it’s done Industrial parboiling Artisanal parboiling 1. Soaking 1. Soaking  Constant temperature (60 -65ºC)  For about 3hours 2. Steaming  Pressure 4–6 kg/cm2  For up to 20min 3. Drying  Initial temperatures (from ambient to >90ºC )  for up to 16 hours 2. Steaming  atmospheric pressure  Duration is variable 3. Drying
  4. 4. Artisanal parboiling Improving artisanal parboiling is a key component of many rice improvement programs in Africa Soaking temperature and steaming time are two critical operations in artisanal parboiling.  inappropriate soaking and steaming regimes during artisanal parboiling result in lower head rice yield than raw-milled paddy (Manful et al., 2009) The effect of soaking and steaming regimes on several other grain quality traits of parboiled rice however remains largely unexplained
  5. 5. Objective To characterize the effects of initial soaking temperature and steaming time on some physicochemical properties of artisanal parboiled rice using Response surface methodology (RSM) • RSM is useful  for modeling and analyses of factors  Predicting and optimizing response variables
  6. 6. Methods Experimental design • Central Rotatable Composite Design (CRCD) – 2 factors namely • soaking temperature: 30-90ᵒC • steaming time: 5-20mins – 14 treatment combinations • Rice variety used: NERICA1 Responses Milling recoveries, appearance, pasting properties, cooking properties, cooked grain texture
  7. 7. Methods Plate 1: Soaking process (300g/900ml water) Plate 2: Steaming process
  8. 8. Results Table 1: Effect of treatment combinations on some quality indices Total milled Cooking Treatment rice yield (%) time (mins) Control (raw rice) 65.3 19 17.6ᵒC/12.5mins 72.3 21 30ᵒC/5mins 71.1 22 30ᵒC/20mins 72.4 24 60ᵒC/2mins 73.7 21 60ᵒC/12.5mins 72.5 21 60ᵒC/23mins 73.5 23 90ᵒC/5mins 74.5 23 90ᵒC/20mins 74.7 21 100ᵒC/12.5mins 74.4 22 Color Index- B 3.5 13.9 10.5 13.9 13.1 12.3 13.8 10.5 13.3 13.3 Cooked grain Hardness (g) 2833 3616 4094 3971 3795 3954 4255 4197 4592 4268
  9. 9. Estimated Response Surface Raw rice HRY = 36.3% Regression Coefficient 23.40 X0(Constant) X1(Soak temp) X2(Steam time) 0.14*** -0.61* X12 2.58×10-3 X22 X1X2 R-square Lack-of-fit 0.04 1.60×10-3 91.37 2.18 ***p<0.001; ** p<0.01; *p<0.05 68 HRY (%) Term 58 48 38 28 30 40 50 60 70 80 90 5 8 11 14 17 20 Steaming time(mins) Soaking temp(°C) Fig 1: Regression coefficients, ANOVA of terms, R2 and lack of fit, and surface plots for effects of factors on head rice yield (HRY)
  10. 10. Estimated Response Surface Regression Coefficient 4.48 X1(Soak temp) -0.05*** X2(Steam time) 0.15 Term X12 0.21×10-5 X22 X1X2 -2.68×10-3 -1.33×10-3 R-square 85.11 Lack-of-fit- 5.29 ***p<0.001; ** Fig 2: 5.2 Chalkiness (%) X0(Constant) Raw rice chalkiness = 8.1% 4.2 3.2 2.2 1.2 30 20 17 14 11 40 50 60 70 80 8 5 Steaming time (mins) 90 Soaking temp(°C) p<0.01; *p<0.05 Regression coefficients, ANOVA of terms, R2 and lack of fit, and surface plots for effects of factors on chalkiness
  11. 11. 5000 90ᵒC/20min 4000 60ᵒC/1.9mins 60ᵒC/23mins 3000 2000 1000 0 8 56 104 152 200 248 296 344 392 440 488 536 584 632 680 728 Viscosity (cP) Raw Time/s Fig3: Pasting profile of selected treatments
  12. 12. Estimated Response Surface Raw rice peak viscosity = 2565cP Term X0(Constant) 1183.69 7.69*** X1(Soak temp) X2(Steam time) -21.88*** X12 X22 X1X2 R-square Lack-of-fit - -0.12*** -0.24 1.11×10-3 99.03 7.90 ***p<0.001; ** Fig 4: p<0.01; *p<0.05 1390 Peak Visc (cP) Regression Coefficient 1190 990 790 590 20 17 14 11 390 8 30 40 50 5 60 70 80 90 Steaming time(mins) Soaking temp(°C) Regression coefficients, ANOVA of terms, R2 and lack of fit, and surface plots for effects of factors on peak viscosity
  13. 13. Chalkiness ≤ 2.0 HRY ≥ 60% Steaming time Optimal region 20 15 10 5 20 30 40 50 60 70 80 Soaking temperature 90 100 Fig5: Overlaid contour plot showing optimal region for good head rice yields (≥ 60%) and low chalkiness (2.0)
  14. 14. Table 5: Validation of results from response surface optimization Validation run Soaking temp (°C) Steaming time (mins) Head Rice Yield (%) Chalkiness (%) 1 80.0 21.0 60.6 1.6 2 30.0 5.0 32.6 3.6 3 90.0 5.0 65.7 1.0 4 90.0 20.0 66.1 0.0 5 17.6 12.5 34.8 2.6 6 60.0 12.5 40.5 1.2 7 100.0 12.5 66.5 0.5
  15. 15. Conclusions To parboil to achieve good head rice yield and low chalkiness:  Optimal range for initial soaking temperature = 80-95ᵒC  Optimal range for steaming time = 22-3mins Parboiling treatments that increase head rice yield also influence on other physicochemical properties such as grain appearance, cooking properties, cooked rice texture and pasting properties. The effect of parboiling on pasting properties suggest that parboiling could be optimized to alter the functional properties of rice in food formulations

×