Discusses in some detail various sorghum milling techniques

Kebakile, Martin M.

English

DigitalCommons@University of Nebraska

University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln INTSORMIL Presentations International Sorghum and Millet Collaborative Research Support Program (INTSORMIL CRSP) 12-2010 Improvements in Sorghum Milling Technologies Martin M. Kebakile National Food Technology Research Centre, martin@naftec.org Follow this and additional works at: https://digitalcommons.unl.edu/intsormilpresent  Part of the Agronomy and Crop Sciences Commons, and the Food Processing Commons Kebakile, Martin M., "Improvements in Sorghum Milling Technologies" (2010). INTSORMIL Presentations. 24. https://digitalcommons.unl.edu/intsormilpresent/24 This Presentation is brought to you for free and open access by the International Sorghum and Millet Collaborative Research Support Program (INTSORMIL CRSP) at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in INTSORMIL Presentations by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. National Food Technology Research CentreEndless possibilities in food researchwww.naftec.org email: mail@naftec.orgImprovements in Sorghum Milling TechnologiesMartin M Kebakile (PhD)martin@naftec.orgNational Food Technology Research CentreEndless possibilities in food researchIntroductionSorghum is staple food for millions in African and Asian countriesIt ranks 5th in production worldwide, but is 2nd most important after maize in AfricaThe crop is adapted to drought conditions and therefore could be a strategic grain for food security in Sub-Saharan AfricaNational Food Technology Research CentreEndless possibilities in food researchLimitationsSorghum has been neglected until recently; Little R&D efforts compared to other common cereals Sorghum food industry is non-vibrant (largely traditional products)Generally there is lack of suitable sorghum food processing technologiesLow production capacityHigh milling losesVariable product qualityNational Food Technology Research CentreEndless possibilities in food researchSorghum millingPurpose of milling is to;Separate the starch-rich endosperm (84 %) from the pericarp (6 %) and the germ (10 %)Reduce the “clean” endosperm to small particles (meal)Critical considerations –efficiency (economics) of milling technology and meal qualityCross section of the sorghum kernelP = PericarpFE = Floury endospermCE = Corneous endospermG = GermNational Food Technology Research CentreEndless possibilities in food researchTwo basic approaches to cereal grain millingBreak open kernel, then scrape endosperm from branMainly used for wheat milling (roller milling)Multiple grinding and separation steps (sifting, aspiration and gravity separation)Pericarp (bran) and germ are first removed by degerming or decortication, then endosperm is reduced to grits or flourTypically used for maizeConventional Beall-type degerminator cause breakage of sorghum endosperm; bran contamination (integral germ and spherical shape)Both approaches have been tried for sorghumNational Food Technology Research CentreEndless possibilities in food researchTrends in development of milling technologiesPerten 1983 - Adaption of wheat roller milling technology for sorghumUneconomical low yieldsProducts of inferior quality (bran contamination)Lately small roller mills (2-3 roller pairs) are gaining popularityOptimisation of milling process with respect to roller gap, tempering, and sievingImproved yields but bran contamination still highNational Food Technology Research CentreEndless possibilities in food researchRoller milling cont.Parameter Abrasive DecorticationRoller MillingMeal extraction (%) 75.7a 83.7bAsh (%) 1.18a 1.29bOil (%) 2.46a 2.64bL 84.6b 82.4aCab 10.8a 11.6bhab 70.5b 68.6aComparison of milling performance of abrasive decortication and roller milling using 10 sorghum varieties with different physico-chemical propertiesOther considerations;Roller mill – narrow particle size distribution; wide for hammer millRoller mill has significantly higher meal output (about 195% higher than abrasive and hammer milling systemRoller mill has high energy efficiency (32 kg meal/1kwh), while abrasive hammer mill produced 12.9 kg meal /1kwhNational Food Technology Research CentreEndless possibilities in food researchDifficulties with separation of branStarch granules in mesocarp makes pericarp very friableForms small bran flakes which are difficult to separate from mealBran layer should be toughened to separate as large flakesSource: Earp et al (2004)Focus on temperingBest tempering moisture contentTreatment temperaturetimeNational Food Technology Research CentreEndless possibilities in food researchOther technologies consideredGerman SchuleSwiss DecomaticDanish United Milling SystemPrairie Research Laboratory (PRL) DehullerPeriTec systemNational Food Technology Research CentreEndless possibilities in food researchPRL Dehuller and hammer millCanadian PRL dehuller was adapted for local conditions in West, Eastern ad Southern Africa, and IndiaDry grain is decorticated by abrasive carborundum disks revolving at high speed in a barrel (fine bran removed by aspiration)Milling package (dehuller & hammer mill) was technically and economically viableGave rise to sorghum industry in the region (service milling for villagers)Adequate technical support by RIIC contributed to industry success in BotswanaNational Food Technology Research CentreEndless possibilities in food researchImrpovements in production capacitiesIncreasing demand for sorghum meal require higher production capacitiesAttempts to build larger dehullers compromised milling efficiency and meal qualityCommercial mills now install normal PRL dehullers in series and/or in parallel 4-5 dehullers feed one hammer millTypical capacities are 2 to 2.5 tons per hrNational Food Technology Research CentreEndless possibilities in food researchProduction capacitiesSome mills now using PeriTec decorticator –Vertical Debranner VCW(Satake Corporation)Debrans by abrasion using revolving carborundum wheels and hexagonal slotted screen (stage 1) and friction (stage 2)Bran is removed by blowing air through the system from bottom to top outletRequires conditioning of grain with 1-3% moisture (by weight)  for 3-5 min before debranning – permits gradual stripping of pericarp layersOffers controlled rate of bran removal, uniformly debranned grains and improved power efficiencyHigh input capacities – 2 to 10 tonsPeriTec system; Used with Satake Corporation’s permissionNational Food Technology Research CentreEndless possibilities in food researchGrain cleaningMillers now installing grain cleaning equipment (sieving, aspiration and metal removal)Necessary for high production capacitiesNational Food Technology Research CentreEndless possibilities in food researchSelection of varietiesMeal quality varies with sorghum varieties usedMillers aim to meet consumer demandsBlending of different varieties commonly practicedTypically hard to intermediate endosperm texture preferredLight coloured meals with medium course texture preferred in Botswana Taste is also importantNational Food Technology Research CentreEndless possibilities in food researchConclusionsAbrasive decortication is still the only appropriate technology for decorticating sorghum to meet consumer preferencesRoller milling has potential as an alternative sorghum milling process but still requires optimisation of the tempering processNational Food Technology Research CentreEndless possibilities in food researchTHANK YOU!

Improvements in Sorghum Milling Technologies

UNL | Libraries

University of Nebraska - Lincoln 
DigitalCommons@University of Nebraska - Lincoln 
INTSORMIL Presentations International Sorghum and Millet Collaborative Research Support Program (INTSORMIL CRSP) 
12-2010 
Improvements in Sorghum Milling Technologies 
Martin M. Kebakile 
National Food Technology Research Centre, martin@naftec.org 
Follow this and additional works at: https://digitalcommons.unl.edu/intsormilpresent 
 Part of the Agronomy and Crop Sciences Commons, and the Food Processing Commons 
Kebakile, Martin M., "Improvements in Sorghum Milling Technologies" (2010). INTSORMIL Presentations. 
24. 
https://digitalcommons.unl.edu/intsormilpresent/24 
This Presentation is brought to you for free and open access by the International Sorghum and Millet Collaborative 
Research Support Program (INTSORMIL CRSP) at DigitalCommons@University of Nebraska - Lincoln. It has been 
accepted for inclusion in INTSORMIL Presentations by an authorized administrator of DigitalCommons@University of 
Nebraska - Lincoln. 
National Food Technology Research Centre
Endless possibilities in food research
www.naftec.org email: mail@naftec.org
Improvements in Sorghum 
Milling Technologies
Martin M Kebakile (PhD)
martin@naftec.org
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Introduction
Sorghum is staple food for 
millions in African and 
Asian countries
It ranks 5th in production 
worldwide, but is 2nd most 
important after maize in 
Africa
The crop is adapted to 
drought conditions and 
therefore could be a 
strategic grain for food 
security in Sub-Saharan 
Africa
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Limitations
Sorghum has been 
neglected until recently; 
Little R&D efforts compared 
to other common cereals 
Sorghum food industry is 
non-vibrant (largely 
traditional products)
Generally there is lack of 
suitable sorghum food 
processing technologies
Low production capacity
High milling loses
Variable product quality
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Sorghum milling
Purpose of milling is to;
Separate the starch-rich 
endosperm (84 %) from the 
pericarp (6 %) and the germ 
(10 %)
Reduce the “clean” 
endosperm to small particles 
(meal)
Critical considerations –
efficiency (economics) of 
milling technology and meal 
quality
Cross section of the sorghum kernel
P = Pericarp
FE = Floury endosperm
CE = Corneous endosperm
G = Germ
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Two basic approaches to cereal grain milling
Break open kernel, then scrape endosperm from bran
Mainly used for wheat milling (roller milling)
Multiple grinding and separation steps (sifting, aspiration and 
gravity separation)
Pericarp (bran) and germ are first removed by 
degerming or decortication, then endosperm is 
reduced to grits or flour
Typically used for maize
Conventional Beall-type degerminator cause breakage of 
sorghum endosperm; bran contamination (integral germ and 
spherical shape)
Both approaches have been tried for sorghum
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Trends in development of milling technologies
Perten 1983 - Adaption of 
wheat roller milling 
technology for sorghum
Uneconomical low yields
Products of inferior quality 
(bran contamination)
Lately small roller mills (2-3 
roller pairs) are gaining 
popularity
Optimisation of milling 
process with respect to roller 
gap, tempering, and sieving
Improved yields but bran 
contamination still high
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Roller milling cont.
Parameter Abrasive 
Decortication
Roller 
Milling
Meal extraction (%) 75.7a 83.7b
Ash (%) 1.18a 1.29b
Oil (%) 2.46a 2.64b
L 84.6b 82.4a
Cab 10.8a 11.6b
hab 70.5b 68.6a
Comparison of milling performance of abrasive decortication and roller milling 
using 10 sorghum varieties with different physico-chemical properties
Other considerations;
Roller mill – narrow particle size distribution; wide for hammer mill
Roller mill has significantly higher meal output (about 195% higher 
than abrasive and hammer milling system
Roller mill has high energy efficiency (32 kg meal/1kwh), while 
abrasive hammer mill produced 12.9 kg meal /1kwh
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Difficulties with separation of bran
Starch granules in mesocarp makes 
pericarp very friable
Forms small bran flakes which are 
difficult to separate from meal
Bran layer should be toughened to 
separate as large flakes
Source: Earp et al (2004)
Focus on tempering
Best tempering moisture content
Treatment temperature
time
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Other technologies considered
German Schule
Swiss Decomatic
Danish United Milling System
Prairie Research Laboratory (PRL) Dehuller
PeriTec system
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PRL Dehuller and hammer mill
Canadian PRL dehuller was 
adapted for local conditions in 
West, Eastern ad Southern Africa, 
and India
Dry grain is decorticated by 
abrasive carborundum disks 
revolving at high speed in a barrel 
(fine bran removed by aspiration)
Milling package (dehuller & hammer 
mill) was technically and 
economically viable
Gave rise to sorghum industry in 
the region (service milling for 
villagers)
Adequate technical support by RIIC 
contributed to industry success in 
Botswana
N
a
ti
o
n
a
l 
F
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 T
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Imrpovements in production capacities
Increasing demand for 
sorghum meal require 
higher production capacities
Attempts to build larger 
dehullers compromised 
milling efficiency and meal 
quality
Commercial mills now install 
normal PRL dehullers in 
series and/or in parallel 
4-5 dehullers feed one 
hammer mill
Typical capacities are 2 to 
2.5 tons per hr
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Production capacities
Some mills now using PeriTec decorticator –
Vertical Debranner VCW(Satake 
Corporation)
Debrans by abrasion using revolving 
carborundum wheels and hexagonal slotted 
screen (stage 1) and friction (stage 2)
Bran is removed by blowing air through the 
system from bottom to top outlet
Requires conditioning of grain with 1-3% 
moisture (by weight)  for 3-5 min before 
debranning – permits gradual stripping of 
pericarp layers
Offers controlled rate of bran removal, 
uniformly debranned grains and improved 
power efficiency
High input capacities – 2 to 10 tons
PeriTec system; Used with 
Satake Corporation’s permission
N
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Grain cleaning
Millers now installing 
grain cleaning 
equipment (sieving, 
aspiration and metal 
removal)
Necessary for high 
production capacities
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Selection of varieties
Meal quality varies with 
sorghum varieties used
Millers aim to meet consumer 
demands
Blending of different varieties 
commonly practiced
Typically hard to intermediate 
endosperm texture preferred
Light coloured meals with 
medium course texture 
preferred in Botswana 
Taste is also important
N
a
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n
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l 
F
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 T
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Conclusions
Abrasive decortication is still the only appropriate 
technology for decorticating sorghum to meet 
consumer preferences
Roller milling has potential as an alternative 
sorghum milling process but still requires 
optimisation of the tempering process
N
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THANK YOU!


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Improvements in Sorghum Milling Technologies

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