Development of an improved parboiling technology for small to medium-scale rice processors in sub-Saharan Africa

S.A. Ndindeng*, J.T. Manful, N. Woin et al, S.Ndindeng@cgiar.org

The problem with rice in SSA is not only the quantity but also the quality

• Rice is fast becoming a global staple and its demand is on the rise especially in Sub Saharan African (SSA) countries.

• The quantity produced is far smaller than what is consumed

• Also the quality of locally produced rice does not satisfy the needs of urban consumers

• Postharvest losses (quantitative and qualitative) in rice in most SAA countries has been attributed to poor postharvest practices and utilization of inappropriate equipment.

• postharvest losses reduction leads to 15–20% increase in rice

Proper parboiling can upgrade the quality of locally produced rice

• Locally produced rice has a high proportion of broken fractions, is of mixed varieties and contains impurities.

• Proper parboiling reduce grain breakages, impurities and improves on the nutritional quality of milled rice.

Parboiling is common in SSA countries like Cameroon, Nigeria, Ghana and Benin but the parboiling procedure and vessel used does not consistently result in high quality parboiled milled rice.

In addition the stove results in high energy loss and exposes the processors to heat burns.

Traditional parboiling

Methodology• Constructed a parboiling vessel and stove in

partnership with Taless-Seimef and MIPROMALO respectively for small to medium scale (10 - 1000 kg per day).

• Determined the optimum soaking temperature, steaming time, drying and milling conditions.

• Compared the outputs of the improved technology (quality of rice produced and energy efficiency) to that of the traditional technology.

Parboiling vessel and stove

Parboiling Stove(Reduction of heat loss)

Parboiling VesselUniform distribution of steam

Main ideas behind the Parboiling Technology developed

Stove uses- Wood or- Charcoal or- Briquettes.

Two Drying Phases1st phase, dry to 18 % MC under the sun

2nd phase, dry to 14 % MC under the shade

Rubber roll or higher type millsParboiling Vessel & Stove

Cleaned Paddy

Soaking, Steaming, Drying and Milling are critical in producing quality parboiled rice

Variety Drying Phases1st to 18 %MC/2nd to 14 % MC

% Head Rice % Rotten grains

TOX3145 Shade/Sun 47.21 0.50TOX3145 Sun/Sun 71.47 0.02TOX3145 Sun/Shade 85.00 0.05

Variety Husk Type Soaking Temp (oC)

Steaming Time (Min)

TOX3145 Thin 80 20

CICA-8 Thick 90 25

TIANAN-5 Thick 90 25

Observed differences in Physical and Cooking characteristics

Rice type (%) HR CG (No./50gr

ains)

HDG(%) Whiteness (CIE L*)

Yellowness (CIE b*)

pH Swelling ratio

Non parboiled

33.46c* 6.33b / 85.52a 11.33b 6.22b 3.26b

Traditional parboiled

55.16b 11.33a 4.38a 57.63c 16.73a 5.78a 3.16b

Improved parboiled

87.71a 1.33c 0.02b 71.39b 11.49b 6.23b 3.53a

HR=Head rice, CG=Cracked grains, HDG= Heat damaged grains* numbers with different superscript letters are significantly different at the 0.05 level

Efficiency of Parboiling Stoves using The Water Boiling Test

stove Phases TTB(min)

BR (g/min)

SFC (g/l)

Fire Power(watts)

TDR

Traditional Cold-start high power

15.06a* 78.53b 487.47b 23889.43b /

Improved 10.06b 208.46a 884.47a 63723.60a /

Traditional Hot-start high power

14.10a 204.56b 1119.50a 62532.50b /

Improved 8.06b 259.96a 884.47b 79653.50a /

Traditional Simmering / 41.50b 18451.80a 12584.50b 1.90b

Improved / 92.60a 16746.33b 28187.46a 2.24a

TTB=Time to boil, BR=Burning rate, SFC= Specific fuel consumption, TDR=Turndown ratio* Numbers with superscript a are higher and different from b at the 0.05 level

Quality dedifferentiation of domestic from imported rice through proper parboiling

16% of consumer think it was imported &- Discounted traditionally parboiled rice

by 2%.

63% of consumer think it was imported &- Paid 5% premium price for improved

parboiled rice.

Traditional parboiling Improved parboiling

Conclusions & Recommendations• The improved parboiling technology produced high

quality rice that mimics premium quality imported rice.

• Consumers were willing to pay 5 % premium price for this rice.

• The stove was more energy efficient and friendly to use than the traditional stove.

• The technology is easy to build at the village level and may be easily adopted by small to medium-scale rice processors in SSA.

Thanks for your kind attention