Cereals ― Classification and grading of sorghum 
grains intended for sale in Botswana  BOTSWANA  STANDARD  BOS  63:2022  
Edition 2.0  BOS  63:2022  
BOTSWANA BUREAU OF STANDARDS  Copyright Protection Notice
© BOBS [ 2022 ] – All rights reserved  
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Website: www.bobstandards.bw  
ICS 67.060  
Published in Botswana  
BOS  63:2022  
Edition 2.0  
© BOBS [202 2] – All rights reserved  
i Contents  Page  
Foreword  ................................ ................................ ................................ ................................ ..................  ii 
1 Scope  ................................ ................................ ................................ ................................ ...........  1 
2 Normative References  ................................ ................................ ................................ ................  1 
3 Definitions  ................................ ................................ ................................ ................................ ... 2 
4 Classes  and grades  of sorghum  ................................ ................................ ................................  2 
4.1 Classes  of sorghum  ................................ ................................ ................................ ....................  2 
4.1.1  Food  class  sorghum  (FOC)  ................................ ................................ ................................ ........  2 
4.1.2  Characteristics  of class  FOC  ................................ ................................ ................................ ..... 3 
4.1.3  Feed  class  sorghum  (FEC)  ................................ ................................ ................................ ........  3 
4.1.4  Malting  class sorghum  (MC)  ................................ ................................ ................................ ...... 3 
4.1.5  Characteristics  of class  MC ................................ ................................ ................................ ....... 3 
4.1.6  Other  class sorghum  (OC)  ................................ ................................ ................................ .........  3 
4.2 Grades  of sorghum  ................................ ................................ ................................ .....................  4 
4.2.1  Class  FOC ................................ ................................ ................................ ................................ .... 4 
4.2.2  Class  FEC ................................ ................................ ................................ ................................ .... 4 
4.2.3  Class  MC ................................ ................................ ................................ ................................ ...... 4 
4.2.4  Class  OC ................................ ................................ ................................ ................................ ...... 5 
4.2.5  Sample  grade  sorghum  ................................ ................................ ................................ ..............  5 
4.3 Requirements  ................................ ................................ ................................ ..............................  5 
4.3.1  Quality  factors  - General  ................................ ................................ ................................ ............  5 
4.3.2  Quality  factors  - Specific ................................ ................................ ................................ ............  5 
4.4 Maximum  deviations  ................................ ................................ ................................ ...................  5 
5 Contaminants  ................................ ................................ ................................ ..............................  5 
5.1 Pesticide  residues  ................................ ................................ ................................ ......................  5 
5.2 Heavy  metals  ................................ ................................ ................................ ...............................  5 
5.3 Mycotoxin  ................................ ................................ ................................ ................................ .... 6 
6 Sampling  ................................ ................................ ................................ ................................ ...... 6 
Annex  A ................................ ................................ ................................ ................................ ....................  7 
Annex  B ................................ ................................ ................................ ................................ .....................  8 
Annex  C ................................ ................................ ................................ ................................ .....................  9 
Annex  D ................................ ................................ ................................ ................................ ................... 11 
Annex  E ................................ ................................ ................................ ................................ ................... 12 
Annex  F ................................ ................................ ................................ ................................ ................... 14 
Annex G  ................................ ................................ ................................ ................................ .................. 16 BOS  63:2022  
Edition 2.0  
ii Foreword  
This Botswana  Standard  was approved  by the Technical  Advisory  Committee  of the Standard  Council  on 
2022-08-09. 
The Botswana  Bureau  of Standards  (BOBS)  was established  under  the Standard  Act No. 16 of 1995  with a 
primary  responsibility  of preparing Botswana  Standards.  
During  the preparation  of this standard,  assistance  was derived  from ARS 462:2016, Sorghu m — Specification  
and Codex  Alimentarius  CXS 172-1989,  Standard  for Sorghum  grains.  
This Botswana  Standard  is a revision  of, cancels  and replaces  BOS  63:2009.  
During  the preparation  of this standard  the following  organizations  were  directly  represented  in the Cereals  and 
Pulses  Technical  Committee:  
Botswana  University  of Agriculture  Mr G Legwaila  (Chairperson)  
and Natural  Resources  – Department  of Crop  
and Soil Sciences  
Botswana  Bureau  of Standards  Mr O J Moje  (Technical  Secretary)  
Bokomo  Mr J Venter  
Bolux  Group  Ms G Ntope  
Botswana  University  of Agriculture  
and Natural  Resources  – Department  of Crop  
and Soil Sciences  Dr. G Malambane  
Botswana  University  of Agriculture  
and Natural  Resources  – Department  of 
Food Science  and Technology  Prof.  G Bultosa  
Jagwa  Investments  Mr J O Jagwer  
Honey  Guide  Ms T M Phiri 
Ministry of Agriculture,  
Department  of Crop  Production  Mr M Khukhutha  
National  Food  Technology Research  Centre  Mr S Mpotokwane  
© BOBS [ 2022 ] – All rights reserved  BOS  63:2022  
Edition 2.0  
 
© BOBS [202 2] – All rights reserved  
1 Cereals ― Classification and grading of sorghum grains   
intended  for sale in Botswana  
 
1 Scope  
This Botswana  Standard  specifies  classes  and grades of  sorghum  grains  intended  for sale  in Botswana.  
2 Normative References  
The following  normative  documents contain  provisions  which,  through  reference  in this text,  
constitute  provisions of this standard. For dated references, subsequent amendments to, or revisions 
of, any of these  publications do not  apply.  However, parties to agreements  based on this standard 
are encouraged to  investigate the possibility of applying the most recent editions of t he normative 
documents indicated below.  For undated references, the latest edition of the normative document 
referred to applies. BOBS maintain  registers  of currently  valid standards.  
 
AOAC  Official  Method  2001.04,  Determination  of Fumonisins B 1 and B2 in corn and corn flakes  — Liquid  
chromatography with  immunoaffinity  column clean  up. 
BOS 26, Cereals ― Sorghum grains for human consumption ― 
Specification.   
BOS  ISO 13690,  Cereals,  pulses and  milled  products  – Sampling  of static  
batches  Botswana  Agricultural Marketing Board  Act, 1974 (Chapter  
74:06);  
Codex  Alimentarius  Volume  7, Cereals,  pulses,  legumes  and derived  products  and vegetable  proteins.  
ISO 605, Pulses — Determination of impurities, size, foreign odours, insects, and species and variety 
— Test methods  
ISO 5223,  Test sieves  for cereals.  
ISO 6561 -1, Fruits, vegetables and derived products — Determination of cadmium content — Part 
1: Method  using  graphite furnace atomic  absorption spectrometry  
ISO 6561 -2, Fruits, vegetables and deriv ed products — Determination of cadmium content — Part 
2: Method  using  flame atomic  absorption spectrometry  
ISO 6633 , Fruits, vegetables and derived products — Determination of lead content — 
Flameless atomic  absorption  spectrometric  method  
ISO 712:1998,  Cereals  and cereals  products  ‒ Determination  of moisture  content  ‒ Routine  reference  
method.  
ISO 9648,  Sorghum  ― Determination  of tannin  content.  
ISO 16050,  Foodstuffs  — Determination  of aflatoxin  B1, and the total content  of aflatoxin  B1, B2, G1 and 
G2 in cereals,  nuts and derived products  — High performance liquid  chromatographic  method  
ISO 1871:2009 Food and Feed products — General guidelines for the determination of nitrogen by the 
kjeldahl  method  
ISO 2171:2007  Cereals,  pulses  and by-products — determination  of ash yield by incineration  BOS  63:2022  
Edition 2.0  
 
© BOBS [202 2] – All rights reserved  
2 ISO 5986:1983  Animal  feeding  stuffs  — determination  of diethyl  ether extract  
3 Definitions  
3.1 defective  grains: pieces  of grain  or grains  of sorghum  which:  
 
a) are broken,  rotten,  mouldy,  smutty,  or otherwise  diseased;  
 
b) the embryo  skin is cracked;  
 
c) grain is  immature;  
 
d) have  been  damaged  by insects,  rodents,  heat,  or any other  means,  but does  not 
include  weather  stained  sorghum;  and, 
 
e) pass  through  a 1.8 mm slotted  sieve.  
 
3.2 filth:  impurities  of animal  origin  including  insects  and parts  of insects.  
 
3.3 foreign  matter:  all organic  or inorganic materials other  than sorghum  grains such  as sticks,  stones,  clods,  
dung,  chaff,  other portions  of the sorghum plant,  other plants  and seeds  of other plants.  
 
3.4 small  grain  sorghum:  whole  sound  sorghum  grains  that are so small  that it will pass  through  a 1.8 mm 
slotted sieve.  
 
3.5 sorghum  grains:  are whole  grains  obtained  from species  of Sorghum  bicolor  (L) Moench,  after 
acomplete  threshing without  any further  treatment.  
 
3.6 noxious seeds: means the seeds or bits of seeds of plant species that may represent a hazard to  human 
or animal health when consumed, including seeds of Argemone mexicana L (Mexican prickly poppy),  
Convolvulus spp. (bindwee), Crotalaria spp. (rattleweed) , Datura spp. (jimson weed), Ipomoea purpurea  
(common morning  glory),  Lolium  temulentum  (darnel  ryegrass), Ricinus  communis  (castor  oil plant)  or 
Xanthium  spp (common cocklebur).  
 
3.7 weather -stained grains: means so rghum grains of which more than one -third of the surface of the  pericarp  
is distinctly  discoloured  by the weather,  but does  not include  sorghum  kernels  with purple  anthocyanic  blotches  
in or on the  pericarp.  
4 Classes  and grades  of sorghum  
4.1 Classes  of sorghum  
There  shall be four classes  of grain  sorghum  as outlined  below.  
 
4.1.1  Food  class  sorghum  (FOC)  
Food  class  sorghum  shall comprise  three  sub-classes:  
 
a) Food  class  sorghum  - White (FOCW);  
 
b) Food  class  sorghum  - Red (FOCR);  
 
c) Food  class  sorghum  - Other  Colour (FOCO);  
 BOS  63:2022  
Edition 2.0  
 
© BOBS [202 2] – All rights reserved  
3 4.1.2  Characteristics  of class  FOC  
A consignment  of sorghum  shall be classified  as class  FOC  sorghum  if it has the following  characteristics:  
 
a) consists  of sorghum  that does  not have  a dark coloured  testa  ; 
 
b) the grains  are of intermediate  to hard endosperm  texture;  
 
c) consists  of either  white  grains  (sub-class  FOCW);  red grains  (sub-class  FOCR);  or is of 
grain  colour  other  than white  or red, or a mixture of  grain  colours  (sub-class  FOCO);  
 
d) is of a FOC cultivar,  as specified by  the Sorghum (Classification and Grading) Regulations of 
Botswana  Agricultural  Marketing Board Act,  1974 (Chapter  74:06).  
 
e) complies  with the requirements  for one of  the grades  of class  FOC sorghum  as set out in Annex  A. 
 
4.1.3  Feed  class  sorghum  (FEC)  
A consignment  of sorghum  shall be classified  as class  FEC sorghum  if it has the following  characteristics:  
 
a) consists  of sorghum that  does  not have  a dark coloured  testa;  
 
b) is of a FOC cultivar, that cannot be graded as of class FOC, or is of a FEC cultivar as 
specified by the  Sorghum  (Classification and Grading) Regulations of Botswana Agricultural 
Marketing Board Act, 1974  (Chapter 74:06) ; 
 
c) complies  with the requirements  for one of  the grades  of class  FEC sorghum  as set out in Annex  A. 
 
4.1.4  Malting  class sorghum  (MC)  
Malting  class  sorghum  shall comprise  two sub-classes:  
 
a) Malting  class  sorghum  with a  dark coloured  testa  (MCDT);  
 
b) Malting  class  sorghum  without  a dark coloured  testa  (MCCT)  
 
4.1.5  Characteristics  of class  MC 
A consignment of  sorghum  shall be classified  as class  MC sorghum  if it has the following  characteristics:  
 
a) consists of  sorghum  that either  has a dark coloured  testa  (sub-class  MCDT);  or that does  
not have  a dark coloured  testa (sub -class  MCCT);  
 
b) the grains  have  a high  germinability  (GE > 90 %) count  on 72 hours.  
 
c) is of a MCDT cultivar or of  a MCCT cultivar, as specified by the Sorghum 
(Classification and  Grading)  Regulations  of Botswana  Agricultural  Marketing  Board  
Act, 1974  (Chapter 74:06);  
 
d) complies  with the requirements  for one of  the grades  of class  MC sorghum  as set out in Annex  A. 
 
4.1.6  Other  class sorghum  (OC)  
A consignment of sorghum shall be classified as Other class sorghum if it does not comply with the  
requirements  for class  FOC,  class  FEC,  or class  MC sorghum.  BOS  63:2022  
Edition 2.0  
 
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4  
4.2  Grades  of sorghum  
The grades  for the different  classes  of sorghum  excluding  the class  sample -grade  is based  on the 
purity  characteristics  of sorghum  outlined in  Annex  A and shall be  as follows:  
 
4.2.1  Class  FOC  
This class  consists  of the following  subclasses  and grades:  
 
a) Sub-class  FOCW;  
 
1) Grade  FOCW  1; 
 
2) Grade  FOCW  2; 
 
b) Sub-class  FOCR;  
 
1) Grade FOCR  1; 
 
2) Grade FOCR 2;  
 
c) Sub-class  FOCO;  
 
1) Grade  FOCO  1; 
 
2) Grade  FOCO  2. 
 
4.2.2  Class  FEC 
This class  consists  of the following  grades:  
 
a) Grade  FEC 1; 
 
b) Grade  FEC 2. 
 
4.2.3  Class  MC 
This class  consists  of the following  subclasses  and grades:  
 
a) Sub-class  MCDT;  
 
1) Grade  MCDT  1; 
 
2) Grade  MCDT  2; 
 
b) Sub-class  MCCT;  
 
1) Grade  MCCT  1; 
 
2) Grade  MCCT  2. 
 BOS  63:2022  
Edition 2.0  
 
© BOBS [202 2] – All rights reserved  
5 4.2.4  Class  OC 
This class  consists  of the following  grades:  
 
a) Grade  OC 1; 
 
b) Grade  OC 2; 
 
4.2.5  Sample  grade  sorghum  
Sorghum  that does  not comply  with the requirements  for any of the above  grades  of sorghum  shall 
be graded  as Sample -grade  sorghum.  Sample  grade  shall not be  used  for either human  or animal  
consumption.  
 
4.3      Requirements  
4.3.1  Quality  factors  - General  
The product  shall meet  the following  quality  factors:  
 
a) safe and suitable  for human  and animal  consumption;  
 
b) free from abnormal  flavours;  and odours.;  
 
c) shall not have filth (including dead insects) and impurities of plant origin, in  amounts 
which may  constitute  a hazard  to human  health;  and, 
 
d) shall not have  noxious and  toxic seeds,  or their components in  amounts  that may constitute  
a hazard  to human health;  and, 
 
e) not be distinctly  blackened  by smut  or not contain  10 or more  smut  balls or  parts  of smut  
balls,  which  are collectively  equivalent  to 10  or more  smut  balls,  per 100 g of sorghum;  
 
 
4.3.2  Quality  factors  - Specific  
Sorghum  grains  may be white, black,  pink, red, brown,  orange,  or yellow  in colour,  or a mixture  of these 
colours.  
 
4.4      Maximum  deviations  
  Maximum  deviations  shall not exceed  those  specified  in Annex A  and Annex B.  
5 Contaminants  
5.1  Pesticide  residues  
Sorghum grains shall comply with those maximum pesticide residue limits established by 
the Codex  Alimentarius  Commission  for this commodity.  
 
5.2   Heavy  metals  
Sorghum grains shall comply with those maximum limits for heavy metal contaminants specified in 
CODEX STAN  193 and in particular  those listed in  Table 1.  
 
 BOS  63:2022  
Edition 2.0  
 
© BOBS [202 2] – All rights reserved  
6 Table  1 —Heavy  metal  contaminants  
 
Parameter  Limit  (ppm  max)  Test method  
Lead  (Pb) 0.1 ISO 6633  
Cadmium  (Cd) 0.02 ISO 6561 -1 or ISO 6561 -2 
 
5.3   Mycotoxin  
Sorghum grain shall comply with the mycotoxin limits established by the Codex Alimentarius 
Commission as  given  in Table 2 when tested in accordance  with the test  methods  specified therein . 
 
Table  2 — Mycotoxins  limits  for Sorghum  grains  
Mycotoxin  limit Test method  
Total  Aflatoxin  
(AFB1+AFB2+AFG1+AFG2),  
ppb, max 10 ISO 16050  
Aflatoxin  B1 ppb, max 5 
Fumonisins  ppm,  max 2 AOAC Official Method  
2001.04  
 
6 Sampling  
Sampling  shall be done  in accordance  with BOS  ISO 13690  and all other  parameters  mentioned  in 
BOS  26 shall be taken  into consideration.  BOS  63:2022  
Edition 2.0  
 
© BOBS [202 2] – All rights reserved  
7  
 
Annex  A 
(normative)  
 
Permissible  purity  characteristics  in sorghum  
Table  A.1 ―  Permissible  purity  characteristics  in sorghum  
 
 
 
 
Nature of  deviation  Maximum  extent  to which  defects are  permissible  in %  
 
Methods of  
analysis  Grade  FOC  Grade  FEC Grade  MC Grade  OC 
GR 1 GR 2 GR 1 GR 2 GR 1 GR 2 GR 1 GR 2 
Foreign  matter  * 1.5 2.0 2.0 3.0 1.5 3.0 2.0 3.0 Visual  
examination  
Unthreshed  sorghum  4.0 6.0 6.0 12.0 6.0 12.0 4.0 6.0 Visual  
examination  
Defective  sorghum  ** 3.0 6.0 10.0 20.0 5 10 4.0 6.0 Annex G  
Small kernel  4.0 8.0 10.0 20.0 8.0 20.0 4.0 8.0 ISO 5223  
Sorghum of other  
classes  2.0 4.0 8.0 10.0 2.0 4.0 2.0 4.0 Visual  
examination  
Sorghum of another  
colour  2.0 4.0 - - 2.0 8.0 - - Annex  D 
Total of the above  
defects  8.0 10.0 10.0 20.0 10.0 20.0 10.0 12.0 Annex G  
Weather stained  
sorghum  25.0 50.0 50.0 75.0 50.0 75.0 50.0 75.0 Visual  
examination  
* of which  inorganic  matter  shall not exceed  0.5 %, and filth shall  not exceed  0.1 %. 
** of which  rotten,  smutty,  or diseased  grain  shall not exceed  0.5 %.  
- denotes  no set specification.  
- GR denotes  grade  BOS  63:2022  
Edition 2.0  
 
© BOBS [202 2] – All rights reserved  
8 Annex  B 
(normative)  
 
Permissible  physico -chemical  characteristics  in sorghum  
 
Table  B.1 ― Permissible  physico -chemical  characteristics  in 
sorghum  
 
Nature of  
deviation  Permissible  levels  in, %  
Methods 
of 
analys
is  
Grade  FOC   
Grade  FEC Grade  MC Grad  e 
OC No dark  
coloured  
testa  Dark  
coloured  
testa  
Moisture  13.0 13.0 13.0 13.0 13.0 ISO 
712 
Tannin  levels  * < 0.5 % < 0.5 % < 0.5 % < 0.3 % < 0.5 % ISO 
9648  
Test weight, Min  
(kg/hl)  71 62 62 62 62 ISO 
605 
Grain  Hardness  Intermediate  
to hard  
endosperm   
 
- Intermediate to  
soft endosperm   
 
-  
 
- Annex 
E 
Ash, MAX;  (on a 
dry matter  basis)  
Decorticated  
sorghum  grains  1.5 1.5 1.5 1.5 1.5 AOAC 923.03 or 
ISO 2171  
Protein  (N X 6.25)  
(MIN; on a dry 
matter  basis)  7 7 7 7 7 ISO 
1871  
Fat (MAX;  on a dry 
mater basis)  4 4 4 4 4 ISO 
5986  
 - denotes  no set specifications  
* Dark  coloured  testa  represented  by tannin  levels  > 0.5 %; and  no dark coloured  testa  by tannin  levels  
< 0.5 % BOS  63:2022  
Edition 2.0  
 
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9 Annex  C 
(informative)  
Detection  of tannin  sorghum  grain  by the bleach  test 
 
C.1 Principle  
 
Sorghum  grain  is immersed  in a sodium  hypochlorite  solution  (bleach)  containing  alkali.  The solution  
dissolves away the outer pericarp layer of sorghum grain, revealing the presence of a black 
pigmented testa  layer  in the case  of tannin  sorghums,  or its absence  in the case of  non-tannin  
sorghums.  
 
C.2 Reage nt 
 
5 g sodium  hydroxide  is dissolved  in 100 ml of 3.5 % sodium  hypochlorite  solution,  commercial  
bleach.  Bleaching  reagent  can be  stored at  room  temperature  in light -proof  bottle  for up to  one month.  
 
C.3 Apparatus  
 
The following  apparatus  shall be used:  
 
a) glass  beakers,  50 ml; 
 
b) tea strainer;  
 
c) aluminium  foil; 
 
d) paper  towel.  
 
e) test must  be performed  in duplicate;  
 
f) known tannin sorghum and non -tannin sorghum standards must be included each time 
the test is  performed;  
 
g) one hundred  whole,  sound  sorghum  grains  are placed  in a beaker;  
 
h) bleaching reagent is added to just cover the sorghum grains and close beaker with 
aluminium foil. Too  much bleaching reagent will cause over bleaching and give false negative 
results. If in doubt repeat  using  less reagent;  
 
i) incubate beaker at room temperature (20°C - 30°C) for 20 min, swirling contents of  
beaker every 5  min; 
 
j) empty contents of beaker into tea strainer, discarding bleaching reagent. Rinse sorghum 
grains in tea  strainer with  tap water;  
 
k) empty contents of tea strainer onto sheet of paper towel. Spread grains out into a single 
layer and  gently blot  them  dry with another  piece  of paper  towel;  
 
l) count tannin sorghum grains. Tannin sorghum grains are those grains that are black over 
the entire  surface of the grain. Non -tannin sorghum grains are those which are either 
completely white, or are  brown  over part of the surface of  the grain.  BOS  63:2022  
Edition 2.0  
 
© BOBS [202 2] – All rights reserved  
10  
C.4 Procedure  
 
The test  method  shall be done  as follows  
 
C.5 Presentation  of results  
 
Calculate  tannin  sorghum  grains as  percentage  of total sorghum  grains.  Duplicate  determinations  
shall not differ  by more  than  5 grains,  for example  first determination  90 %, second  determination  
85 %, or 95 
%. The mean  of the duplicate  determinations  shall be calculated.  
 
C.6 Expression  of results  
 
Results  shall be expressed  as percentage  tannin  sorghum,  e.g. 90 % tannin sorghum.  BOS  63:2022  
Edition 2.0  
 
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11 Annex  D 
(normative ) 
Classification  of sorghum  grain  according  to colour  
 
D.1 Principle  
Sorghum  grains  are viewed  with the naked  eye. Sorghum  grains  are classified  as being  either  ‘white’  
or ‘coloured’.  
 
D.2   Apparatus  
Sheets  of white  (A4) paper shall  be used.  
 
D.3  Procedure  
The test method  shall be done as  follows:  
 
a) test shall be performed  in duplicate;  
 
b) known  white  and coloured  sorghum  standards  shall be included  each  time the test is performed;  
 
c) count  out 100 intact  sorghum  grains  without  glumes  and spread  evenly  over the  surface  of 
the sheet  of white paper  so that  none of  the grains  are touching  each other;  
 
d) examine  the grains  and count  the number  of “white”  or ‘coloured’  grains,  which  ever is the least.  
 
NOTE  A ‘white’  grain is  coloured  white  all over its surface,  irrespective  of whether  the grain is  
‘weathered’  i.e. shows  signs  of mould  on its surface,  and/or  has purplish  anthocyanic  
blotches  on its surface.  
A ‘coloured’  grain  is coloured  yellow,  pink,  red, brown,  or purple  (or combinations  of these  colours)  all over 
its surface.  
D.4  Presentation  of results  
D.4.1  Calculation  
Calculate  white  (or coloured)  sorghum  grains  as percentage  of total sorghum  gr
ains.  Duplicate  determinations  shall not differ  by more  than  5 grains,  for example  first determination  
90 
%, second  determination  85 %, or 95 %. The mean  of the duplicate  determinations  shall be 
calculated  as a whole number.  
 
D.4.2   Expression of  results  
Results  shall be expressed  as percentage  white  or coloured  sorghum,  e.g. 90 % white  sorghum.  BOS  63:2022  
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12 Annex  E 
(normative)  
Estimation  of sorghum  grain  hardness  
E.1 Principle  
 
Sorghum  grains are cut into halves longitudinally. One half is viewed with the naked eye and the 
proportion  of corneous endosperm is determined by reference to a standard. On the basis of the 
proportion of corneous  endosperm,  grains  are classified  into: hard,  intermediate  and soft.  
 
E.2 Apparatus  
The following  apparatus  shall be used:  
 
a) sharp  disposable  scalpel  or sharp  single -edged  razor  blade;  
 
b) blunt  ended  forceps;  
 
c) magnifying  glass;  
 
d) sheets  of (A4) paper, preferably  dark coloured;  
 
e) rubbery  gum used  to attach  posters  to walls,  for example  Prestik.  
 
E.3 Procedure  
The test  method  shall be done  as follows:  
 
a) test shall be performed  in duplicate;  
 
b) press a small piece of  ‘rubbery gum’, approximately the same size as a sorghum kernel onto 
the cutting surface, approximately 5 sheets of white paper. Push a sound sorghum grain germ 
side up into  the side of the piece of ‘rubbery gum’ to hold it in place. The germ side has a 
circular indentation at the  end of grain;  
 
c) hold grain with forceps and cut the grain in two lengthwise, to produce two  even size halves, 
so that  each  half contains  an equal  portion of  the germ;  
 
d) repeat  until 20 grains  have  been  cut; 
 
e) compare  one half of each  grain  against  the illustration  Figure  E.1 and classify  it as: 
 
1) hard  – the endosperm  is totally  corneous  (translucent)  or most  (>50 %) of the 
endosperm  is translucent;  
 
2) medium  – the outer,  corneous  endosperm  is continuous,  but comprises  less than 50 
% of the total endosperm;  the inner  part of the endosperm  being  floury  (having a  
chalky  appearance);  
 
3) soft – the endosperm  is totally  floury  or the outer,  corneous  endosperm  is very 
narrow  and incomplete.  
 BOS  63:2022  
Edition 2.0  
 
© BOBS [202 2] – All rights reserved  
13 E.4  Presentation  of results  
E4.1  Calculation  
Calculate  the number  of hard,  medium  and soft and grains  as a percentage   of  total   sorghum  
grains. Duplicate determinations shall not differ by more than  1 grain in each class. The mean of 
the duplicate determinations shall  be calculated  as a whole number . 
E4.2  Expression of  results  
 
Results  shall be expressed  as percentage  of hard,  medium  and soft sorghum  grains,  e.g. 
 
Table  E.1 ‒ Expression  of results  of sorghum  grain hardness  
 
Grain  hardness,  (%) Hard  Medium  Soft 
Sample  ,X 85 10 5 
 
  
 
 
 
 
 
 
Figure  E.1 ‒ Visual  estimation  of grain  hardness  BOS  63:2022  
Edition 2.0  
 
© BOBS [202 2] – All rights reserved  
14 Annex  F 
(normative)  
Determination  of germinative  energy  of sorghum  grain  
 
F.1 Principle  
Sorghum grains are placed on damp filter paper in closed petri dishes and allowed to germinate at a 
set temperature for set periods of  time. The percentage of grains that has germinated at the end of  
each period  is calculated.  
 
F.2  Apparatus  
The following  apparatus  shall be used:  
 
a) incubator set  at 25 °C  and 100 %  relative  humidity;  
 
b) petri dishes  (glass  or plastic)  10 cm diameter  with lids; 
 
c) filter paper (Whatman  No. 1) 9 cm diameter;  
 
d) graduated  pipette  with 4 ml measure;  
e) distilled  water.  
 
F.3  Procedure  
The test  method  shall be done  as follows:  
 
a) test shall be performed  in duplicate;  
b) moisten  the filter paper  with 4 ml of distilled  water;  
 
c) place  two filter paper circles  into the bottom  of the petri dish;  
d) count out 100 intact sorghum grains and spread evenly over the surface of the moistened filter 
paper  so that none  of the grains  are touching  each  other.  Close the petri  dish;  
 
e) place the  filled petri dishes  in the incubator;  
f) after 24 h, 48 h and 72 h, the grains are examined. At each time interval, the germinated grains 
are counted and removed from the petri dish. Germinated grains are grains where the root has 
penetrated  the pericarp,  i.e. the grain  has chitted.  
 
F.4  Presentation  of results  
 
F.4.1  Calculation  
At each  time interval  calculate  the percentage -germinated  grains.  Duplicate  determinations  shall 
not differ  by more  than  5 grains,  for example  first determination  95 %, second  determination  90 %, 
or 100 
%. Germinative  energy  is the mean  of the duplicate  determinations,  expressed  as a whole  number.  
 
 BOS  63:2022  
Edition 2.0  
 
© BOBS [202 2] – All rights reserved  
15 F.4.2  Expression  of results  
Results  shall be expressed  as germinative  energy  (%) 24 h, 48 h, 72 h, e.g.  
Table  F.1 ‒ Expression  of results of  germinative  energy  of 
sorghum  grain  
 
Germinative Energy (%) 24 h 48 h 72 h 
Sample  X 84 92 95 
 
 BOS  63:2022  
Edition 2.0  
 
© BOBS [202 2] – All rights reserved  
16 Annex  G 
(normative)  
 
Determination  of total  defects  in sorghum  grain 
 
G.1 Principle  
 
The principle  of the method  is to separate  all defects  from the normal  basic  grains  by manual  selection.  
 
G.2 Reagents  
 
No reagents  are required  for this determination.  
 
G.3 Apparatus  
 
The following  apparatus  shall be used:  
 
a) balance  of precision  0.1 g; 
 
b) sheet  of cardboard approximately A4 size on which is drawn a 20 cm  x 20 cm  square divided 
into 400 x 1 cm square blocks with a 10 cm x10 cm square marked in the corner of the larger 
square  (Figure G.1). If  determination is to be carried out routinely, it is recommended that the 
square should  be drawn  on A4 sized piece of  wood,  metal  or plastic,  or on paper  and then 
laminated;  
 
c) thin object  with straight  flat edge,  for example  15 cm ruler;  
 
G.4 Procedure  
 
The test method  shall be as follows:  
 
a) test shall be performed  in duplicate;  
 
b) weigh  out an average  (final)  sample  of 25.0 g and empty  sample  onto A4 sheet;  
 
c) spread  sample  into a monolayer  on the 10 cm x 10 cm square.  The sample  shall 
approximately  fill the square;  
 
d) with the aid of the ruler move  all defects  described  out of  the 10 cm x 10 cm square  
 
e) when  all the entire  sample  has been  carefully  and completely  sorted  through  and all 
defects  have  been  moved  out of the 10 cm square  block,  with the aid of the ruler 
systematically  fill the 1 cm square  blocks  with a monolayer  of defects.  There  must  be no 
space  between  the defects;  
 
f) count  the number  of 1cm squares  of defects.  If there  is a square  that contains  less than 1 
square  cm of defects  it shall be counted as  a full square.  
 BOS  63:2022  
Edition 2.0  
 
© BOBS [202 2] – All rights reserved  
17 
G.5 Presentation  of results  
 
G 5.1 Calculation  
 
Express  total defects  as percentage  of the sample.  The formula  below  shall be used  to convert  the 
number  of squares  of total defects  into percentage  total defects.  
 
% Total  defects  = number  squares  of defects  x 0.5 
 
Duplicate  determinations  shall not differ  by more  than   2 squares,  for example  first 
determination  10 squares  (5 %), second determination  8 squares  (4 %), or 12 squares  (6 %). 
 
The mean  of the duplicate  determinations  shall be calculated  
G 5.2 Expression  of results  
 
Results  shall be expressed  as percentage  total defects  of sorghum  grain,  e.g. 5 % 
 
NOTE  
 20 cm x 20 cm square  grid for sorting  total defects  from sound  whole  
sorghum  grains,With  10 cm x 10 sm insert  for checking  sample  size 
 
Figure  G.1 ‒ Square  grid for sorting  total  defects