KENYA STANDARD                                   DKS 2061: 2016  
ICS 67.100.10  
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Raw whole camel milk — Specification  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 ©KEBS                   First Edition 2016 
 
 
 
TECHNICAL COMMITTEE REPRESENTATION  
 DKS 2061: 2007  
 
©KEBS 2016 — All rights reserved  
 ii The following organizations were  represented on the Technical Committee  
 
Kenya Dairy Board  
Ministry of Health — Public Health Department  
Directorate of Livestock  Production  
Directorate of Veterinary  Services  
Egerton University — Department of Dairy and Food Science Technology  
Government Chemist’s Department  
National Public Health Labs  
Kenya Industr ial Research and Development Institute (KIRDI)  
Consumer Information Network  
New Kenya Creameries Cooperative (NKCC)  
Brookside Dairy Ltd.  
Eldoville Dairies Limited  
Githunguri Dairy  
Happy Cow Ltd  
Sameer Agriculture and Livestock (K) Limited  
KIBIDAV  Ltd (T OGGS)  
Kenya Camel Association (KCA)  
Regional Pastoral livelihood  resilience Project  
Agricultural sector Development Support programme (ASDSP)  
University of Nairobi  
Kenya Bureau of Standards — Secretariat  
 
 
 
 
 
REVISION OF KENYA STANDARDS  
 
In order to keep a breast of progress in industry, Kenya Standards shall be regularly reviewed. Suggestions  for 
improvements to published standards, addressed to the Managing Director, Kenya Bureau of Standards, are 
welcome.  
 
 
 
 
© Kenya Bureau of Standards, 2007  
 
Copyright. Users are reminded that by virtue of section 25 of the Copyright Act, Cap. 12 of  2001 of the Laws of Kenya, copyright subsists in 
all Kenya Standards and except as provided under section 26 of this Act, no Kenya Standard produced by Kenya Bureau of Standa rds may 
be reproduced, stored in a retrieval system in any form or transmitted by any means without prior permission in writing from the Managing 
Director.  
 
 
 
 
 
 
 
 
 KENYA STANDAR D                                  DKS 2061: 2016  
ICS 67.100.10  
©KEBS 20 16 — All rights reserved  
 iii  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Raw whole camel milk — Specification  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 DKS 2061: 2007  
 
©KEBS 2016 — All rights reserved  
 iv  
 
 
 
KENYA  BUREAU OF STANDARDS (KEBS)  
 
Head Office:  P.O. Box 54974, Nairobi -00200, Tel.: (+254 020) 605490, 602350, Fax: (+254 020) 604031  
E-Mail: info@kebs.org,  Web:http://www.kebs.org  
 
Coast Region Region       Lake Region                     Rift Valley  
P.O. Box 99376 , Mombasa -80100                 P.O. Box 2949,  Kisumu -40100                 P.O. Box 2138, Nakuru -20100  
Tel.: (+254 041) 229563, 230939/40               Tel.: (+254 057)  23549, 22396                 Tel.: (+254 051) 210553, 210555  
Fax: (+254 041) 22944 8    Fax: (+254 057) 21814        
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Foreword  
 KENYA STANDAR D                                  DKS 2061: 2016  
ICS 67.100.10  
©KEBS 20 16 — All rights reserved  
 v This Kenya Standard was prepared by the Milk and Milk Products Technical Committee under the guidance of 
the Standards Project Committee and it is in accordance with the procedu res of the Kenya Bureau of Standards.  
 
The d airy cattle sub -sector contributes to 4 % of National Gross Domestic Product (GDP) . However the  
contribution of dairy camel sub -sector  is not reflected in the National economic report . This is due to lack of 
marke t competiveness in the dairy camel sector. In Kenya, t he estimated camel population is about 3 million , 
with annual camel milk production of 940  thousand tonnes  (940 million litres)  in 2013; indicating that dairy camel 
sub-sector offers a huge potential f or improving the livelihoods  of communities living in Arid and Semi -Arid Lands 
(ASAL ). Various agencies have made efforts to improve the market competiveness of dairy camel sub -sector 
through development of camel milk standards.  
 
The standard  for raw whol e camel milk were first develo ped in 2006 and adapted in 2007 . Currently there is new 
scientific data and evidence on quality and safety of camel milk ; hence the need to review the existing raw whole 
camel milk standard (KS 2016:2007) to reflect the true s ituation in the camel milk sub -sector.  
 
The standard addresses quality and safety requirements of raw whole camel milk; including Annexes on carrying   
out the rapid tests.  
 
During the preparation of this standard reference was made to various documents an d extensive consultation 
with stakeholders.  
 
Acknowledgement is hereby made for the assistance derived from these sources.  
 
 KENYA STANDARD                                 DKS 2061: 20 16 
©KEBS 20 16 — All rights reserved  1  
Raw whole camel milk — Specification  
 
1 Scope  
 
This Kenya standard specifies  the requirements and  methods of sampling and test f or raw whole camel milk.  
 
2 Normative references  
 
The following contain provisions, which, through reference in this text constitute provisions of this standard. All 
standards are subject to revision and any reference to a standard is deemed to be a refere nce to the latest 
edition of that standard, parties to agreements based on this standard are encouraged to take steps to ensure 
the use of the most recent editions of the documents indicated:  
 
AOAC 922.08, Determination of Hypoc hlorite and chloramins in mi lk- Colorimetric method  
AOAC 942.17, Determination of Arsenic in foods - Molybdenum  blue method  
AOAC 947.05; Determination of Acidity of milk - trimetric method  
AOAC 960.27, Determination of preservatives in milk  
AOAC 962.16, Determination of Beta-lactam Ant ibiotics in milk  
AOAC 980.21, Determination of Aflatoxin M1 in milk and cheese -thin layer chromatographic method  
AOAC 999.10, Lead, Cadmium, Copper, Iron, and Zinc in foods, Atomic Absorption Spectrophotometry after dry 
ashing  
CAC/MRL 1; Maximum Residue Li mits (MRLs) for pesticides  
CAC/MRL 3 Maximum Residue Limits (MRLs) and Risk Management Recommendations (RMRs) for Residues 
of Veterinary Drugs in Foods  
KS CODEX STAN 193, Codex general standard for contamina nts and toxins in foods  
KS ISO 2446, Milk — Determination of fat content (Routine method)  
KS ISO 4831:2006; Microbiology of food and animal feeding stuffs - Horizontal method for the detection and 
enumeration of coliforms - Most probable number technique)  
KS ISO 4832; 2006; Microbiology of food and animal feeding stuffs - Horizontal method for the enumeration of 
coliforms - Colony -count technique  
KS ISO 4833 -1; Microbiology of the food chain -- Horizontal method for the enumeration of microorganisms -- 
Part 1: Colony count at 30 degrees C by the pour plate technique  
KS ISO 5738:2004 (IDF 76:2004) ; Milk and milk products -- Determination of copper content -- Photometric 
method (Reference method  
KS ISO 5764, Milk - Determination of freezing point - Thermistor cr yoscope method (Reference method)  
KS ISO 6785, Milk and milk products -- Detection of Salmonella spp  
KS ISO 6611, Milk and milk products  Enumeration of colony -forming units of yeasts and/or moulds  Colony -
count technique at 25 degrees C  
KS ISO 6731, Mi lk, cream and evaporated milk - Determination of total solids content (reference method)  
KS ISO 6732; Milk and milk products -- Determination of iron content -- Spectrometric method (Reference 
method)  
KS ISO/TS 6733:2006 (IDF/RM 133:2006) ; Milk and milk products -- Determination of lead content -- Graphite 
furnace atomic absorption spectrometric method  
KS 1552 , Code of hygienic practice for milk  and milk produ cts  
 
 
 
3 Terms and Definition s 
 
For the purpose of this Standard, the following definition shall apply.  
 
3.1  KS 2061: 20 16 
 
    ©KEBS 2016 — All rights reserved  
 2 raw whole camel milk  
it shall mean the normal, clean and fresh secretion obtained by practically emptying the udder of a healthy 
camel , but exclu ding that obtained during the first seven days after calving and free from colostrum  
 
4 Essential Quality  and compositional requirements   
 
4.1     General Requirements  
 
Raw whole camel milk;  
 
4.1.1 Shall  not have any foreign matter.  
 
4.1.2 Shall  not have a ny foul odour  and taints . 
 
4.1.3 Shall  have characteristic white colour.  
 
4.1.4    Shall  not be  mixed with milk from any other Livestock  
 
4.2.5 Shall  not contain added water, preservatives, or other added substances, nor shall any proportion of a 
natural c onstituent be removed.  
 
 
4.2  Principal  Compositional requirements  
 
Raw whole camel milk shall comply with the compositional requirements given in Table 1 below .  
 
Table  1 — Compositional requirements  
 
Sl No.  Characteristic  Limits  Test methods  
i) Milk fat , % min.  2% KS ISO 2446  
ii) Solids not fat, % min.  6% KS ISO  6731  
iii) Density at 20 ºC  1.026 g/mL – 1.035 g/mL  AOAC 961.07  
 
iv) Freezing point depression  0.518°C to  0.530°C   KS ISO 5764  
v) pH 6.4 – 6.7 PH Meter ; Annex C  
iv) Total acidity  (expressed  as 
% of lactic acid),max  
 0.17% to 0.21%  KS ISO/TS 11869  
 
 
 
4.3 Rapid tests  
 
The camel milk shall comply with the rapid tests described in Annex A – H. 
 
5 Microbiological limits  
 
5.1 Total viable  count , the plate shall be incubated for 48 h  at 32  °C.  
 
 
 KS 2061: 2016  
 
©KEBS 2016 — All rights reserved  
 3 Table 2 — Total Viable count  
 
Grade  Counts  
(per ml)  
I.  < 200 000  
II.  >200 000 ⎯ 1 000 000  
III.  >1 000 000 ⎯ 2 000 000  
 
 
5.2 Coliform  count,  the plate shall be incubated for 24 h at 37  °C.   
Table 3 — Coliform limits  
 Grade  Counts (per ml)  
I 0-1000  
II 1000 -50000  
III 50000 - 100000  
 
 
 
6 Contaminants  
 
The products covered by this stan dard shall comply with the maximum levels of CODEX STAN 193 and the 
maximum residue limits for pesticides and veterinary drugs established by the Codex Alimentarius Commission 
(CAC).  
 
5.1       Heavy metals  
 
Heavy metal limits for raw whole camel milk shal l be as given in Table 4.  
 
 
Table 4 — Limits for heavy metal contaminants raw whole camel  milk 
 
 
SL No   
Heavy metal   
MRL  
(max.)   
Test method  
i) Arsenic (AS)  
 0.1 mg/kg  
  AOAC 942.17  
ii) Lead (Pb)  
 0.02 mg/kg  
 KS ISO 6733  
iii) Mercury (Hg)  1.0 mg/kg  
 AOAC 999.10  
iv) Copper (Cu)  
 5.0 mg/kg  
 AOAC 960.40/  
KS ISO 5738  
v) Zinc (Zn)  
 50 mg/kg  AOAC 999.10  
vi)  
Tin (Sn)  250   mg/kg  AOAC 999.10  
vii) Cadmium as Cd,  1.5 mg/kg  AOAC 999.10  KS 2061: 20 16 
 
    ©KEBS 2016 — All rights reserved  
 4   
viii) Iron (fe),  
 0.5 mg/kg  KS ISO 6732  
 
 
 
5.2       Mycotoxin res idues  
 
Raw whole camel milk shall not have more than 0.015 ppb aflatoxin M1 content when tested according to KS 
ISO 14501 or AOAC 980.21.  
 
 
5.3           Veterinary drug residues    
The products covered by this standard shall comply with those maximum limi ts for veterinary drug residue limits 
established by the Codex Alimentarius Commission in; Codex general standard for contaminants and toxins in 
foods  and feed (Codex  Stan 193)  
 
 
5.3.1       Antibiotic  residues  
 
Raw whole camel  milk shall not have more tha n 10.0 ppb beta lactam  content of antibiotic residues as beta 
lactam  content when tested according to AOAC 962.16 and when analyzed by the appropriate approved 
methods as given in the Food, Drugs and Chemical Substances Act, Cap. 254 of the Laws of  Kenya a nd the 
CODEX guidance   
 
 
 
5.4 Pesticide residues  
 
Raw whole camel milk shall conform to th e maximum limits for pesticide  residues, established  by the Codex 
Alimentarius Commission for these products in Codex general standard for contaminants and toxins in foods  and 
feed (Codex Stan 193)  
 
 
 
6 HYGIENE  
 
6.1 The raw whole camel milk  shall be  handled in accordance with KS 1552:2016 and other relevant Kenya 
standards and regulations. The raw whole camel milk shall comply with microbiological criteria 
established in accordance with KS CAC/GL 21 .  
 
6.2 It shall be transported in clean and sanitized containers made of approved food grade materials and 
shall comply with the relevant Kenya standards.  
 
 
 
 
 
 
 
 
 KS 2061: 2016  
 
©KEBS 2016 — All rights reserved  
 5 Annex  A 
(normative)  
 
Organoleptic test and temperature  
 
A.1 General 
 
Judging the quality of milk by its taste and smell requires considerable skill, which could only be acquired by 
training and practice.  Organoleptic tests are used in all dairies and an experienced person can pick out bad 
samples with a high degree o f accuracy.  
 
A.2 Procedure to be adopted on the receiving platform  
 
A.2.1 Foreign matter  
  
Presence of the foreign matter such as pieces of dung, hair or any other foreign material should be checked.  
A.2.2 Colo ur 
  
Observe the color of the milk.  If abnorm al in color, it shall be isolated and subjected to confirmatory tests.   
 
 
 
A.2.3.1 Odour   
 
A.2.3.1.1 Smell the milk in the container immediately after removing the lid.  In case of foul odour  and taints , it 
shall be isolated and subjected to confirmatory t ests 
 
A.2.3.2.1 Those due to developed acidity.  This is the most important factor to be examined when grading milk 
by organoleptic test.  
 
A.2.4.2 .1 Those due to feed, or exposure of milk to air or contamination from containers.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 KS 2061: 20 16 
 
    ©KEBS 2016 — All rights reserved  
 6 Annex B  
(normative)  
 
Determination of insoluble matter  
B.1 Sediment test  
B.1.1  Sediment test on raw milk reveals the extent to which visible insoluble matter has gained entrance to the 
milk and the extent to which such material has not been removed from milk by s ingle service strainers.  
The Sediment test represents a simple, rapid and quantitative measure of indicating the cleanliness of milk with 
respect to visible dirt.  
Allow a measured quantity of milk to pass through a fixed area of a filter disc and compare t he sediment left with 
the prepared standards.  
B.1.2  Apparatus  
a) Sediment tester w ith filtering surface 24 mm in diameter.  
b) White lintine cotton discs , 32 mm in diameter, expected filtration area 28 mm in diameter.  
c) Sampling dipper , of 500 ml capacity for sampling from milk cans or weighing vats. Standard sediment discs 
Use commercially available standard sediment discs  
B.1.3  Procedure  
Take a milk sample from well -stirred cans or vats of milk with the sampling dipper. Measure the quantity used 
with reas onable accuracy. Filter the milk through a properly adjusted, firm lintine cotton disc (rough side facing 
milk) held in the sediment tester so that a filtration area of 28 mm is exposed. Compare the sediment disc with 
the prepared sediment standard discs a nd record the sediment score.  
B.1.4  Interpretation  
For the purpose of comparison, it is convenient to use about five prepared standard discs so as to classify the 
milk with respect to its sediment content in accordance with the specific requirement of the dairy or the milk 
collection depot. For the former, five discs showing 0.1, 0.2, 0.5, 1.0 and 2.0 mg may suffice. Under rural 
conditions, discs showing 0.0, 0.5, 2.0, 5.0 and 7.0 mg sediment may be more convenient to start with. In either 
case, no attempt shall be made to estimate the degree of sediment in milk in more than five classes, for 
example, Excellent, Good, Fair, Bad and Very Bad. No attempt shall be made to grade as sediment any hair, 
flies, piece of hay or straw or any large particles of dirt. T hese shall be reported separately.  
The presence of appreciable sediment in unprocessed milk supplies indicates careless or insanitary dairy farm 
practice. However, the lack of sediment is not always indicative of ideal conditions, since visible Sediment ma y 
be readily removed by straining at the dairy farm.  
 
 
 
 
 
 KS 2061: 2016  
 
©KEBS 2016 — All rights reserved  
 7  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Annex  C 
(normative)  
 
Determination of pH  
 
C.1 General  
 
The pH value or hydrogen ion concentration gives a measure of the true acidity of milk.  The relationship 
between p H and ac idity of milk is only approximate.  In normal camel milk  the p H ranges from 6.4  to 6.7.  The 
value is reduced by the development of acidity.  On the other hand, the p H value of milk from a camel  infected 
with mastitis is alkaline in reaction, the value bei ng over 7.0.  The p H of milk may be determined rapidl y by using  
any appropriate method.  
 
C.2 Indicator strips  
 
Indicator paper strips or discs are made by soaking strips of absorbent paper in a suitable indicator and drying 
them.  
 
A rough estimate of pH   is obtained by dipping a strip of the prepared paper in milk and observing the colour.  
Bromocresol purple ( pH range  6.4 to 6.7 – colour  changes from straw yellow to bluish -green) are commonly 
used as indicators.  Both narrow and wide range ready -made ind icator papers are available over the p H range  
6.4 to 6.7. 
 
NOTE  Indicator paper strips shall always be kept in closed glass bottles and dry conditions.  
 
C.3 Interpretation  
 
In normal milk the p H is well below 6.7 on  an average, camel milk  gives a p H of 6.4  to 6.7. Milk of p H over 6.9 
should be regarded with suspicion as indication of some diseases of the udder or of late lactation milk.  
 
 
 
 
 
 
 KS 2061: 20 16 
 
    ©KEBS 2016 — All rights reserved  
 8  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Annex  D 
(normative)  
 
Alcohol test  
D.1 General  
 
The alcohol test is used for rapid assessment of stability of milk to processing, particularly for condensing and 
sterilization.  
 
The alcohol test is useful as an indication of the mineral balance of milk and not so much as an index of 
developed acidity.  The test aids in detecting abnormal milk, such  as a colostrums, milk from animals in late 
lactation, milk from animals infected with  mastitis and milk in which the mineral balance has been disturbed.  
 
D.2 Apparatus  
 
D.2.1 Test-tubes , 150 mm x 19 mm, preferably with graduation marks at 5 ml and 10 ml / or alcohol gun. 
 
D.2.2 Measure for alcohol , for 5 ml. 
 
D.3 Reagents  
 
D.3.1 Ethyl alcohol , 70-75 % by volume (density 0.867  5 g/ml at 27  0C). 
 
D.4 Procedure  
 
Place 5 ml of milk in a test tube and add an equal quantity of alcohol.  Mix the contents of the t est tube by inverting several 
times.  Note any flakes or clots.  The presence of a flake or a clot denotes a positive test.  
 
D.5 Interpretation  
 
A negative test indicates low acidity and good heat stability of milk sample.   
 
NOTE  Milk showing positive is no t considered suitable for the manufacture of evaporated milk which has to be sterilized to ensure its 
keeping quality.  KS 2061: 2016  
 
©KEBS 2016 — All rights reserved  
 9  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 KS 2061: 20 16 
 
    ©KEBS 2016 — All rights reserved  
 10 Annex  
(informative)  
 
Ten-minute resazurin test  
G.1 General  
This test provides a rapid measure of the sanitary  condition and keeping quality of milk. Resazurin reduction 
occurs in two stages, the first an irreversible change from the blue resazurin to the pink resorufin and the second 
a reversible change from the pink resorufin and the second a reversible change f rom the pink resorufin to the 
colourless dihyroresorufin. The first stage of reduction or colour change from blue to pink is fairly easily brought 
about so that the quality of milk is assessed in much shorter time. Taking advantage of the two -stage reducti on, 
several procedures have been proposed for reading the end point of resazurin test.  
With fresh milk the observed change is resazurin reduction is due to the bacteria present and the leucocytes 
content. The reduction brought about by leucocytes, however,  diminishes with the age of milk. Reduction can be 
assumed to be brought by the leucocytes if the colour in the down graded milk sample (for example, milk from 
animals suffering from mastitis) remains unchanged for a longer time than observed normally.  
The test is intended as a platform test for detecting milk of poor keeping quality and shall be carried out on 
samples collected for bacteriological analysis.  
G.2 Apparatus  
a) Sterile test -tube without rims ,150 mm x 16 mm internal diameter 13.5 mm ± 0.5 mm a ccurately 
marked at 10 ml. If not used directly after sterilization, they shall be kept in closed boxes protected from dust.  
b) Sterilized rubber stoppers , for closing the test tubes. The stoppers are sterilized by immersing in a 
boiling water bath for no t less than 10 min.  
c) Sterile 1 ml pipettes , straight -sided, blow -out delivery pipettes for measuring the dye solution (see G.3) 
shall preferably comply with the following specifications:  
Overall length                                            300 mm  
External diameter                                      7.5 mm to 8.5 mm  
Graduation                                                one mark only at 1 ml level  
Distance of graduation from tips                140 mm to 180 mm  
Internal diameter                                       2.3 mm to 3.0 mm  
The pipettes shall also be calibrated to deliver 1 ml of water at 27 °C when the contents are blown out with the 
tip touching the side of the vessel, three seconds allowed for drainage and the accumulated drop then blo wn out. 
No pipette should have an error of more than ± 2 %, that is, the amount delivered should be between 0.98 ml 
and 1.02 ml.  
d) Sterile 10 ml pipettes , Straight -sided, blowout type.  
e) Sampling dippers , These shall be sterilized by keeping in boiling w ater for 30 min. Water shall be 
changed at frequent intervals when a series of samples are to be examined.  KS 2061: 2016  
 
©KEBS 2016 — All rights reserved  
 11 f) Pipette case of metal.  
g) Water -bath , Maintained at 37.5 °C ± 0.5 °C, fitted with a cover to exclude light and containing a metal 
rack designed to  hold test tubes when immersed in water. The water -bath shall preferably be thermostatically 
controlled. The level of water in the bath shall be maintained above the level of the milk in the tubes. The interior 
of the bath shall be completely dark.  
h) Stop watch.  
i) Hot air oven autoclave or steam -sterilizer.  
j) Wire baskets, for holding test tubes.  
k) Glass marking pencil.  
l) Bunsen burner or spirit lamp.  
m) Comparator with standard resazurin disc. The comparator may be provided with artificial daylight so urce 
of illumination.  
n) Sterile 50 ml measuring flask or cylinder.  
o) Glass distiller, for preparing distilled water.  
G.3 Reagents  
Sterile standard resazurin solution  
Prepare 0.05 % (W/V) stock solution by resazurin in glass distilled Prepare 0.05 % (W/V)  stock solution by 
resazurin in glass distilled, sterilized water. Preserve in tightly stoppered amber -coloured bottle in a refrigerator. 
Prepare a 0.005 % bench solution by diluting with sterile water. It shall be prepared fresh after every 8 h. When 
actually not in use, keep it in a cool dark place.  
NOTE - Resazurin powder shall conform to the following requirements:  
i) It shall contain sodium resazurate equivalent to 60 ± 3 % resazurin.  
ii) Apart from traces of sodium resocefate, no other dyestuff shall be pres ent. 
iii) The remaining part shall consist of sodium carbonate and/or sodium acetate and moisture only.  
iv) It shall give a colourless water -clear solution on reduction in alkaline solution.  
v) At a concentration of 1 to 220 000 in fresh normal mixed cow milk o f 3.4 % fat, it shall give a tinto -meter disc 
reading of not less than 6.  
G.4 Procedure  
Start the test as soon as possible after a group of samples has been taken and at least within 30 min.  
Shake the sample container at least 25 times, each shake being an  up and down movement with an excursion of 
about 30 cm, the whole process of shaking not exceeding 12 s. After shaking, take 10 ml for the test in the test 
tube. Place the tubes in numerical order, with the thumb and fingers of the left hand, taking care n ot to touch the 
mouth of the tube. Measure 1 ml of the resazurin solution with a sterile pipette, insert the pipette about half an 
inch into the mouth of the tube and expel the solution by blowing.  KS 2061: 20 16 
 
    ©KEBS 2016 — All rights reserved  
 12 Replace the stopper, by inverting the tube twice in 4 s an d return to the rack. When resazurin has been added to 
a batch of not more than five tubes, place immediately in the water -bath and note the time. The delivery jet of the 
pipette shall not touch the milk in the tube. Any pipette becoming contaminated shall  be immediately discarded. 
Use a fresh sterile pipette for every group of five samples.  
At the end of 10 min and 30 s, remove the tubes from the water -bath and immediately match the colour with the 
resazurin disc in the comparator, recording the results fo r the tubes in the right section.  
The comparator and stand are placed on a bench at such a height that the operator is able to look down on the 
two apertures. The disc is then revolved until the sample is matched and the disc reading noted. When the 
colour  falls between two disc numbers, it shall be recorded as the half value; for example, a reading between 3 
and 4 shall be recorded as 3.5.  
Tubes giving a reading between 0 and 1, streaky pink or very pale pink are recorded as 0.5.  
NOTE  It is an advantage fo r two persons to work in a team when a number of samples are to be taken rapidly, one to 
take the samples and the other to handle the containers and check the identity of the samples. Similarly, at the time of 
reading one person to watch the tubes and anot her to record.  
G.5 Precautions  
The following precautions are necessary to get consistent results:  
a) All testers should be trained to correctly match the colours in the comparator.  
b) The control and experimental test tubes shall be of the same type and th ickness of glass.  
c) Control samples used shall be from the same consignment as milk tested to compensate for the natural 
colour of milk.  
d) Resazurin solution, milk, and milk to which resazurin has been added shall not be exposed to direct 
sunlight in the  laboratory.  
e) The water -bath shall be kept covered during the test.  
f) The temperature of the water -bath shall be checked before commencing each batch of tests.  
G.6 Interpretation  
The results shall be interpreted as follows:  
Disc reading                                Keeping quality  
4 or higher                                    Satisfactory  
3.5 to 1                                         Doubtful  
4 or higher                                    Unsatisfactory  KS 2061: 2016  
 
©KEBS 2016 — All rights reserved  
 13 Note:  Ten-minute resazurin test should be us ed in complementary with other tests  Annex G  
(normative)  
 
Clot-on-boiling (C.O.B.) test  
G.1 General  
This is a quick test to determine developed acidity and the suitability of milk for processing.  
G.2 Apparatus  
a) Test-tube: 15.6 cm x 1.9 cm , preferably wi th a mark at 5 ml;  
b) Water -bath. 
G.3 Procedure  
Transfer 5 ml of the sample to the test -tube and smell. Place the tube in a boiling water -bath and hold for about 
5 min, and smell again for any acidic flavour. Remove the tube and rotate it in an almost hori zontal position and 
examine the film of milk or side of the test -tube for any precipitated particles.  The formation of clots indicative of 
a positive test.  
G.4 Interpretation  
The principal features of the boiling test are speed and definiteness of results.  Milk either remains unchanged or 
coagulates. Milk, which gives a positive C.O.B. test, has acidity generally above 0.17 % (as lactic acid) and is not 
suitable for distribution as liquid milk or for processing.