DRAFT UGANDA STANDARD  
 DUS 154 8 
First Edition  
2013-mm-dd 
 
 
 Reference number  
DUS 154 8:2013 
© UNBS 2013  
  
Raw goat  milk — Specification  
 DUS 1548:2013 
ii © UNBS 2013 – All rights reserved  
 Compliance with this standard does not, of itself confer immunity from legal obligations  
A Uganda Standard does not purport to include all necessary provisions of a contract. Users are 
responsible for its correct applicatio n 
© UNBS 201 3  
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilised in any 
form or by any means, electronic or mechanical, including photocopying and microfilm, without prior written 
permission from UNB S. 
Requests for permission to reproduce this document should be addressed to  
The Executive Director  
Uganda National Bureau of Standards  
P.O. Box 6329  
Kampala  
Uganda  
Tel: 256 41 4 505 995  
Fax: 256 41 4 286 123  
E-mail: info@unbs.co.ug  
Web: www.unbs.go.ug  
 
 DUS 1548:2013 
© UNBS 2013 – All rights reserved  iii 
 Foreword  
Uganda National Bureau of Standards (UNBS) is a parastata l under the Ministry of Trade, Industry and 
Cooperatives established under Cap 327 , of the Laws of Uganda.  UNBS is mandated to co -ordinate the 
elaboratio n of standards and is :  
(a) a member of International Organisati on for Standardisation (ISO);   
(b) a contact point for the WHO/FAO Codex Alimentari us Commission on Food Standards;  and  
(c) the National Enquiry Point on TBT/SPS Agreements of the World Trade Organisati on (WTO).  
The work of preparing Uganda Standards is carried out through Technical Committees. A Technical 
Committee is established to deliberate on standards in a given field or area and consists of representatives of 
consumers, traders, academicians, manu facturers, government and other stakeholders.  
Draft Uganda Standards adopted by the Technical Committee are widely circulated to stakeholders and the 
general public for comments. The committee reviews the comments before recommending the draft standards 
for approval and declaration as Uganda Standards by the National Standards Council.  
This Draft Uganda Standard has been developed as a result of a need  to provide guidance  in producti on of 
safe and quality raw goat  milk.  
Committee membership  
The following o rganisations were represented under the Milk and milk products and processes  sub-committee 
of the Food and Agriculture Standards Technical Committee, UNBS/TC 2, during the development of this 
standard:  
  DRAFT UGANDA STANDARD  DUS 154 8:2013 
 
© UNBS 2013– All rights reserved  1 
 Raw goat  milk — Specification  
1 Scope  
This Draft Uga nda S tandard specif ies requirements and methods of sampling and test for raw goat  milk. 
2 Normative references  
The following referenced documents are indispensable for the application of this document. For dated 
references, only the edition cited applies. For undated references, the latest edition of the referenced 
document (including any amendments) applies.  
US 7, General standard for labelling of pre -packaged foods  
US 28, Code of practice for hygiene in the food and drink manufacturing industry   
US 45, General standard for food additives  
US 201, Drinking (potable) water — Specification  
US 738,  General standard for contaminants and toxins in food  and feed  
US 163 , Code of hygienic practice for milk and milk products  
US EAS 68 -1, Milk and milk products — Meth ods for microbiological examination – Part 1: Total plate count   
US EAS 68 -2-1, Milk and milk products — Methods for microbiological examination — Part 2 -1: Enumeration 
of coliforms ─ Colony count technique at 30 °C   
US EAS 161, Milk and milk products — Sampling — Inspection by attributes — Specification  
US EAS 162, Milk, cream and evaporated milk — Determination of total solids content (reference method)  
US EAS 164, Milk — Determination of fat content (Routine method)  
US EAS 165, Milk and milk products — Inspecting sampling — Inspection by variables  
ISO 5764, Milk — Determination of freezing point — Thermistor cryoscope method (Reference method)  
ISO 6731, Milk, cream and evaporated milk — Determination of total solids content (Reference method)  
ISO 8968 -5, Milk — Determination of nitrogen content — Part 5: Determination of protein -nitrogen content  
ISO 22662 , Milk and milk products — Determination of lactose content by high -performance liquid 
chromatography (Reference method)  
ISO 11866, Milk and milk products  — Enumeration of presumptive Escherichia coli  
ISO 13366, Milk — Enumeration of somatic cells    
2 © UNBS 2013 – All rights reserved  
 3 Terms and definitions  
For the purposes of this standard, the following terms and definitions shall apply.  
3.1 
raw goat milk  
normal, clean and fresh secretions extracted  from the udder of a healthy mother goat (Capra spp.) , properly 
fed and kept, but excluding that got during the first three (3)  days after giving birth  
3.2 
foreign matter  
any foreign substance which may affect the appearance, flavour  and taste of the milk 
3.3 
colostrum  
a form of milk produced by a mother goat just prior to giving birth  
4 Requirements  
4.1 General quality requirements  
Raw goat milk shall: 
a) be obtained from healthy mother goats ( Capra spp.) ;  
b) be of natural flavour without any foreign matter and adulteration ; 
c) be free from colostrums;  
d) not be treated except by cooling ; 
e) not be decomposed ; and  
f) not contain added water, preservatives, or other added substances, nor shall any proportion of a 
natural constituent be removed.  
4.2 Essential physio -chemical requirements  
4.2.1  Raw goat milk  shall comply with the physio -chemical requirements indicate in Table 1.  
Table 1 — Physio -chemical requirements for Raw goat milk  
S/N Characteristic  Requirement  Method s of test  
i Fat content , %, min.  3.25 US EAS 1 64 
ii Protein content , %, min.  3.5 ISO 8968 -5 
iii Lactose content, % , min.  4.2 ISO 22662  
iii Solids Not Fat (SNF) , %, min.  8.25 ISO 6731  
iv Density at 20 
 C, g/ml  1.028  – 1.036   
v Freezing point depression, 
 C 0.525 – 0.550  ISO 5764  
vi Titratable aci dity as lactic acid,  % 0.1 – 0.2  
vii pH 6.5 – 6.8 Annex C  
 DUS 1548: 2013 
© UNBS 2013 – All rights reserved  3 
 4.2.2  When tested in accordance with the appropriate method s in Annexes A to H , raw goat milk shall:  
a) have a characteristic creamy – white colour , free from off flavours and taints ; 
b) be free of ob jectionable matter ; 
c) not coagulate in the clot on boiling test ; 
d) test negative to the alcohol test ; and 
e) test negative to peroxidase test.  
5 Hygiene  
5.1 General  
Raw goat  milk shall be produced and handled in accordance with US 163 and US 28 . 
5.2 Bacteriologi cal Grades   
Raw goat milk shall be free from pathogenic organisms and shall comply with the microbiological limits 
indicated in Table 2 and 3 below.  
5.2.1 Total plate count  
The plate shall be incubated for 48 h at 32 
 C. The counts shall be graded as foll ows: 
Table 2  
 Total plate count  limits  
Grade  Counts (per ml)  Method  of test  
I < 200 000   
US EAS 68 -1 
 II >200 000 
  1 000 000  
III >1 000 000 
  2 000 000  
 
5.2.2 Coliform plate count  
The plate shall be incubated for 24 h at 37 
 C. The counts shall be graded as follows:  
Table 3  — Coliform limits  
S/N Quality  Counts (per ml)  Method  of test  
a) Very good  0 – 1000  
US EAS 68 -2-1 
b) Good  1000 - 50000  
 
5.2.3 Somatic cell count  
Somatic cell count shall not exceed 300 000 per ml when tested in accordance wit h ISO 13366.   
4 © UNBS 2013 – All rights reserved  
 6 Contaminants  
6.1 Heavy metals  and other contaminants  
Raw goat milk shall comply with those maximum limits for heavy metals and other contaminants specified in 
US 738 . 
6.2  Pesticides and veterinary drug residues  
Raw goat milk shall comply wi th those maximum pesticide s and veterinary drug residue limits established by 
the Codex Alimentarius Commission .  
7 Packing and storing  
7.1 Raw goat milk collected from milking shall  be kept in a clean container with a good hygienic  practice 
before and aft er use.  
7.2 Raw goat milk from milking shall  be immediately delivered to the collection center. I n case of non 
delivery, it shall be stored at 4 °C or below and not longer than 24 hours . In case raw goat milk has to be 
stored longer than 24 hours, it shoul d be frozen at -18 °C or below  provided  the delivery time from farm to the 
processing factory is within 15 days.  
7.3 Raw goat milk in the storage ta nk of the collection center shall  be kept at 4 °C or below and not longer 
than 24 hours prior to delivering to processing factory.  
8 Transportation  
8.1 Carriage used for delivering raw goat milk from farm to collection center must be in a clean and safe 
condition for transportation. In case of non -cooling, the milk shall  be immediately delivered within 2 hours.  
8.2 Carriage or container used for delivery raw goat milk from collection c enter to processing factory shall  
keep milk temperature properly and prevent contamination during transportation.  
9 Methods of sampling and test  
Rapid platform tests on quality of raw goat milk shall be done in accordance with Annexes A to H . DUS 1548: 2013 
© UNBS 2013 – All rights reserved  5 
 Annex A  
(normative)  
 
Organoleptic test and temperature  
A.1 General  
Judging the quality of milk by its physical and sensory characteristics requires considerable skill, which could 
only be acqui red by practice. Organoleptic tests are used in all dairies and an experienced person can pick 
out bad samples with a high degree of accuracy.  
A.2 Procedure to be adopted on the receiving platform  
A.2.1  Colour  
Observe the colour of the milk.  If abnormal in colour, it should be held over for subjection to confirmatory 
tests.  
A.2.2  Odour and Taints  
Smell the milk in the container immediately after removing the lid.  In case of foul or abnormal smell, hold over 
the milk for subjection to confirmatory tests.  
  
6 © UNBS 2013 – All rights reserved  
 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 m ilk by single 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 c ompare the 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 f or sampling from milk cans or weighing vats.  
d) 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 rea sonable 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 and 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. These 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 
may be readily removed by straining at the dairy farm.  DUS 1548: 2013 
© UNBS 2013 – 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 pH and acidity of milk is only appr oximate. In normal cow milk the pH ranges from 6.6 to 6.8. The 
value is reduced by the development of acidity. On the other hand, the pH value of milk from a cow suffering 
from mastitis is alkaline in reaction, the value being over 7.0. The pH test is main ly used for the detection of 
abnormal mastitis in milk. The pH of milk may be determined rapidly by using the indicator strips.  
C.2 Indicator strips  
Indicator paper strips or discs are made by soaking strips of absorbent paper in a suitable indicator and d rying 
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 5.2 to 6.8 colour changes from yellow to purple) and bromothymol blue (pH 
range 6.0 to 7.6 Colour changes  from straw yellow to bluish -green) are commonly used as indicators. Both 
narrow and wide range ready -made indicator papers are available over the pH range 2.0 to 10.5.  
NOTE:  Indicator paper strips shall always be kept in closed glass bottles and under dry  conditions.  
C.3 Interpretation  
In normal milk the pH is well below 6.9. On an average, cow milk gives a pH of 6.6. Milk of pH over 6.9 should 
be regarded with suspicion as indication of some diseases of the udder or of late lactation milk.  
  
8 © UNBS 2013 – All rights reserved  
 Annex D  
(norma tive) 
 
Clot-on-boiling (C.O.B.) test  
D.1 General  
This is a quick test  to determine developed aci dity and the suitability of milk for processing.  
D.2 Apparatus  
a) Test-tube: 15.6 cm x 1.9 cm , preferably with a mark at 5 ml.  
b) Water -bath . 
D.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 horizontal 
position and examine the film of milk or side of th e test -tube f or any precipitated particles. The formation of 
clots indicative of a positive test.  
D.4 Interpretation  
The principal features of the boiling test are speed and definiteness of results. Milk either re mains 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.  
 DUS 1548: 2013 
© UNBS 2013 – All rights reserved  9 
 Annex E  
(normative)  
 
Alcohol test  
E.1 General  
The alcohol test is used for rapid assessment of stabili ty 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 as much as an index of 
developed acidity. The test aids in det ecting abnormal milk, such as colostru m, milk from animals in late 
lactation, milk from animals suffering from mastitis and which the mineral balance has been disturbed.  
E.2 Apparatus  
a) Test-tubes , 150 mm x 19 mm, preferably with graduation marks at 5 ml and 10 ml.  
b) Measure for alcohol , For 5 ml.  
E.3 Reagent  
Ethyl Alcohol, 68 % by weight or 75 % by volume (density 0.8675 g/ml at 27 
 C). 
E.4 Procedure  
Place 5 ml of milk in a test tube and add an equal quantity of alcohol. Mix the contents of the test tube by 
inverting several times.  
Note any flakes  or clots. The presence of a flake or a clot denotes a positive test.  
E.5 Interpretation  
A negative test indicates low acidity and good heat stability of milk sample.  
Milk showing positive is not considered suitable for the manufacture of evaporated milk, which has to be 
sterilized to ensure its keeping quality.  
  
10 © UNBS 2013 – All rights reserved  
 Annex F  
(informative)  
 
Alizarin -alcohol test  
F.1 General  
This test is similar to the alcohol test and the incorporation of alizarin helps to indicate the approximate 
percentage of acidity.  
F.2 Appa ratus  
Same apparatus as described in E.2.  
F.3 Reagent  
Alizarin Solution, 0.2 % in eth yl alcohol (6.8 %by weight or 75 % by volume, density 0.867 5 g/ml at 27 OC). 
F.4 Procedure  
Place 5 ml of milk in a test -tube and add an equal quantity of the alizarin sol ution. Mix the contents of the test -
tube by inverting several times. Note the colour of the mixture an d presence of flakes or clots. Also note 
whether the flakes, if any, are small or large.  
F.5 Interpretation  
The general interpretation of the results is a s indicated for the alcohol test (see E.5). For acidity of 0.14 % 
upwards, the graduation in size of the flakes and colour is approximately as follows:  
Colour   Size of flakes   Approximate acidity (per cent lactic acid)  
Lilac       Up to 0.14  
Pale red        0.4 to 0.17  
Reddish -brown to brown   Small flakes     0.17 to 0.20  
Brownish -yellow   Large f lakes     Over 0.20  
If acidity has not developed and yet coagulation occurs, it indicates the presence of rennet producing bacteria 
(sweet curdling).  Milk from anim als suffering from mastitis is alkaline in reaction and when mixed with alizarin -
alcohol solution, violet or purple colour is produced. From the practical point of view, it is of little material 
difference whether milk clots through the production of acid or the production of rennin by bacteria as in either 
case it is unstable to heat.  
 DUS 1548: 2013 
© UNBS 2013 – All rights reserved  11 
 Annex G  
(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 from 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 reduction, 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 poo r 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 accurately 
marked at 10 ml. If not used directly after sterilizatio n, 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 not less than 10 min.  
c) Sterile 1 ml pipettes , straight -sided, blow -out del ivery 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 18 0 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 b lown 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 water  for 30 min. Water shall be 
changed at frequent intervals when a series of samples are to be examined.   
12 © UNBS 2013 – All rights reserved  
 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 a ir 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 
source of illumination.  
n) Steril e 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, 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 per cent resazurin.  
ii. Apart from traces of sodium resocefate, no other dyestuff shall be present.  
iii. The remaining part shall consist of sodium carbonate and/or sodium acetate and moisture on ly. 
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 of 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 not to 
touch the mouth of the tube.  Measure 1 ml of the resazurin solution with a sterile pipette, ins ert the pipette 
about half an inch into the mouth of the tube and expel the solution by blowing.  
Replace the stopper, by inverting the tube twice in 4 s and return to the rack. When resazurin has been added DUS 1548: 2013 
© UNBS 2013 – All rights reserved  13 
 to a batch of not more than five tubes, place imm ediately 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 for the tubes in the right section. The comparator 
and stand are placed on a bench at such a height tha t 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 betwe en 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 for two persons to work in a team when a number of samples are to be taken rapidly, one to 
take the sam ples and the other to handle the containers and chec k the identity of the samples. Similarly, at the time of 
reading one person to watch the tubes and another 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 thickness 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 che cked 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  
Below 1    Unsatisfactory   
14 © UNBS 2013 – All rights reserved  
 Annex H  
(informative)  
 
Half-hour methylene blu e reduction (m.b.r.) test  
H.1 General  
The length of time taken by milk to decolourise methylene blue is a fairly good measure of its bacterial content 
and hence its sanitary and keeping quality.  
H.2 Apparatus  
Same as in G.2.  
H.3 Reagent  
Methylene blue solu tion  
Prepare a standard solution of methylene blue by dissolving one of the good quality methylene blue 
thiocyanate tablets in 200 ml of cold, sterile, glass -distilled water in a sterile flask. It is preferable to allow the 
mixture to stand for several ho urs to ensure complete solution.  
Depending on the nature of methylene blue tablets used, sometimes the stock solution is further diluted with 
800 ml of sterile glass distilled water A concentration of 1 part of methylene blue thiocyanate in 300 000 parts 
of milk is used to obtain satisfactory results. The solution shall be stored in a sterile glass -stoppered amber -
coloured bottle in a dark place and at no time exposed to light.  The solution remains stable in the dark for a 
considerable time but no stock so lution more than two months old shall be used  
The amount of methylene blue required for a day's work shall be poured off from the stock bottle into a 
suitable glass container. On no account shall the pipette used for transferring the methylene blue solutio n to 
the tubes of milk be introduced into the stock bottle.  Moreover, if at any time during the filling of the tubes 
methylene blue solution should become contaminated with milk carried into it by a pipette, which has 
inadvertently come into contact with the milk, the methylene blue solution shall be immediately discarded and 
replaced by a fresh stock.  
H.4 Procedure  
Thoroughly mix the sample of the milk by inverting and shaking the sample bottle as described in Clause G3 
and then pour the milk in the test -tube up to the 10 ml mark.  
While doing this, remove the stopper or cap of the bottle under aseptic conditions, the pouring lip of the bottle 
and the mouth of the test -tube being flamed, and then pour the milk rapidly into the tube up to the 10 ml mark. 
While pouring into the tube, take care to leave one side of the interior unwetted with milk. Add 1 ml of 
methylene blue solution to the tube from a pipette taking care that the pipette does not come into contact with 
any of the milk in the tube or with the we t side of the interior of the tube.  
If this occurs, discard the pipette immediately. During delivery, hold the tip of the pipette against the dry side of 
the tube about 1 cm to 2 cm above the level of the milk and expel the methylene blue solution by blowi ng with 
the mouth or by means of a jet in the pipette. After the lapse of 3 s, blow out the solution remaining in the tip of 
the pipette and withdraw the pipette. Close the tube with sterile forceps or by the tips of the fingers on the DUS 1548: 2013 
© UNBS 2013 – All rights reserved  15 
 extreme upper end. O n no account shall the fingers come into contact with the mouth of the test -tube or end 
of the stopper which comes into contact with the test -tube.  Invert the tube slowly once or twice so that the 
whole column of contained air rises above the level of the  milk and then within 5 min, place the tube in the 
water -bath.  
Put up the following control tubes with each batch:  
i) 10 ml of mixed milk + 1 ml of tap water.  
ii) 10 ml of mixed milk + 1 ml of methylene blue solution.  
The milk for the control tubes shall c onsist of a mixture of milk, preferably from several products, so as to have 
an average fat con tent and colour. Fit the control tubes at (i) and (ii) with stoppers and immerse for 3 min in 
boiling water in order to destroy the natural reducing system pres ent in the milk.  
Comparison of the experimental tubes with control tube (ii) will show when decolourization begins and 
comparison with control tube (i) will show when it is complete.  
Inspect the tube after 30 min. Regard the milk as decolourized when the w hole column of milk is completely 
decolourized or is completely decolourized up to within 5 mm of the surface. If a trace of colour persists at the 
bottom of the tube and does not extend upwards for more than 5 mm, it may be ignored.  Record the time at 
which decolourization is observed. Where a tube is found not to be decolourized within 30 min, the sample 
conforms to the test.  
H.5 Precautions  
The following precautions shall be taken:  
a) It is important that the methylene blue solution when not in use should be kept in the dark. It shall at no 
time be exposed to sunlight.  
b) It is essential that the interior of the water -bath during the progress of the tests shall be completely dark 
since sunlight; diffused daylight and even artificial light catalyze the reductio n of methylene blue.  
c) The sterilization of the rubber stoppers for the test tubes and their subsequent satisfactory manipulation 
can be facilitated by employing a simple rack for holding a large number or rubber stoppers immersed in a 
suitable vessel of boi ling water.  
d) The precautions against the contamination of the milk sample described in the method for carrying out the 
test shall be carefully observed.  
H.6 Interpretation  
The samples, which show complete decolourization of blue colour on incubation for 30 min or less shall not be 
suitable for acceptance.   
16 © UNBS 2013 – All rights reserved  
 Bibliography  
[1] TAS 6006 -2008, Thai Agricultural Standard on Raw goat milk  
 DUS 1548: 2013 
© UNBS 2013– All rights reserved  17 
 Certification marking  
Products that conform to Uganda standards may be marked with Uganda National Bureau of Standards 
(UNBS) Certif ication Mark shown in the figure below.  
The use of the UNBS Certification Mark is governed by the Standards Act, and the Regulations made 
thereunder. This mark can be used only by those licensed under the certification mark scheme operated by 
the Uganda N ational Bureau of Standards and in conjunction with the relevant Uganda Standard. The 
presence of this mark on a product or in relation to a product is an assurance that the goods comply with the 
requirements of that standard under a system of supervision,  control and testing in accordance with the 
certification mark scheme of the Uganda National Bureau of Standards. UNBS marked products are 
continually checked by UNBS for conformity to that standard.  
Further particulars of the terms and conditions of lice nsing may be obtained from the Director, Uganda 
National Bureau of Standards.  
 
 DUS 1548: 2013   
 
ICS 67.100.10 
Price based on nn pages  
© UNBS  2013 – All rights reserved