UGANDA STANDARD  
  DUS 1548  
Second  Edition  
2019 -mm-dd 
 
 
 Reference number  
DUS 1548 : 2019 
© UNBS 2019   
  
Raw goat milk  — Specification   
 DUS  1548 : 2019  
ii © UNBS 2019  – All rights reser ved 
 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 applicati on 
© UNBS 2019   
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 UN BS. 
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 4 333 2 50/1/2/3  
Fax: +256 41 4 286 123  
E-mail: info@unbs.go.ug  
Web: www.unbs.go.ug  
 
. DUS 2145 : 2019  
© UNBS 2019  – All rights reserved  iii 
 Foreword  
Uganda National Bureau of Standards (UNBS) is a parastatal under the Ministry of Trade , Industry and 
Cooperatives established under Cap 327 , of the Laws of Uganda , as amended .  UNBS is mandated to co -
ordinate the elaboration of standards and is  
(a) a member of International Organisation for Standardisation (ISO) and  
(b) a contact point for the WHO/FAO Codex Alimentarius Commission on Food Standards, and  
(c) the National Enquiry Point on TBT  Agreement  of the Worl d Trade Organisation (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 key stakeholders 
including government, academia, consumer groups, private sector and other interested parties.  
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 recommen ding the draft standards 
for approval and declaration as Uganda Standards by the National Standards Council.  
The committee responsible for this document is Technical Committee UNBS /TC 2, [Food and Agriculture]  
Subcommittee SC 1, [Milk and milk products ]. 
This second edition  
 
 
 DUS 1548: 2019   
. 
© UNBS 201 9 – All rights reserved   5  
  Raw goat milk — Specification  
1 Scope   
This Draft Uganda  Standard specifies requirements , sampling and test methods for raw goat  milk. 
2 Normative references   
The following referenced documents referred to in the text in such a way th at some or all of their content 
constitutes requirements 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 EAS 39 , Code of pr actice for hygiene in the food and drink manufacturing industry  
US ISO 2446, Milk – Determination of fat content  
US ISO 6731 , Milk, cream and evaporated milk – Determination of total solids content (Reference method)  
US 45 , General standard for food additi ves 
AOAC 999.10, Official method for lead, cadmium, zinc, copper, and iron in foods Atomic absorption 
Spectrophotometry after microwave Digestion  
US ISO 14501 , Milk and milk powder – Determination of Aflatoxin M1 content – Clean -up by immunoaffinity 
chroma tography and determination by high -performance liquid chromatograph  
US 163, Code of hygienic practice for milk and milk products  
US 738, General standard for contaminants and toxins in food and feed  
US ISO 707, Milk and milk products – Guidance on sampli ng  
US ISO 2446, Milk — Determination of fat content   
US ISO 4832, Microbiology of food and animal feeding stuffs — Horizontal method for the enumeration of 
coliforms — Colony -count technique   
US US ISO 4833 -1, Microbiology of the food chain — Horizontal method for the enumeration of 
microorganisms — Part 1: Colony -count at 30 °C by the pour plate technique  
US ISO 4833 -2, Microbiology of the food chain — Horizontal method for the enumeration of microorganisms 
— Part 2: Colony -count at 30 °C by the surface  plating technique  
US ISO 5538, Milk and milk products — Sampling — Inspection by attributes   
US ISO 5764, Milk — Determination of freezing point — Thermistor cryoscope method (Reference method)  
US ISO 6731, Milk, cream and evaporated milk — Determinatio n of total solids content (reference method)   UGANDA STANDARD  US   154 8 :201     DUS 1548: 2019  
6  © UNBS 201 9 – All rights reserved  
  US ISO 8197, Milk and milk products — Sampling — Inspection by variables  
US ISO 8968 -1, Milk — Determination of nitrogen content — Part 1: Kjeldahl method   
US ISO 13366 -1, Milk — Enumeration of somatic cells  — Part 1: Microscopic method (Reference method)   
US ISO 22662, Milk and milk products — Determination of lactose content by high -performance liquid 
chromatography (Reference method)  
3 Terms and definitions   
For the purposes of this document, the following t erms and definitions apply.  
:  
ISO and IEC maintain terminological databases for use in standardization at the following addresses:  
— ISO Online browsing platform: available at http://www.iso.org/obp  
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 or  obtained during the first three (3) days 
after kidding  
3.2 
Foreign matte r 
any foreign substance which may affect the appearance, flavour and t aste of the milk  
3.2 
Colostrum  
form of milk produced by a mother goat just prior to kidding  
4 Requirements  
4.1 General Requirements . 
Raw goat milk shall:  
a) be obtained from healthy mother goats (Capra spp.);   
b) be of natural flavour without any foreign matte r and adulteration;  
c) pass the goat milk authentication test when test in accordance to Annex K 
d) be free from colostrums;  
e) not be treated except by cooling;  
f) not be decomposed;  
g) not contain added water, preservatives, or other added substances, nor shall any  proportion of a 
natural constituent be removed  
h) have a characteristic creamy white colour, free from off -flavours and taints;  DUS 1548: 2019   
  
 
© UNBS 2019  – All rights reserved   7  
  i) be free of objectionable matter;  
j) not coagulate in the clot on boiling test  when tested according to Annex D ;  
k) test negative to t he alcohol test; when tested according to Annex E and  
l) test positive to peroxidase test  
4.2  Specific requirements  
Raw goat  milk shall comply with the limits given in Table 1  
Table 1- Chemica l requirements for raw goat milk  
Characteristic  Requirement  Methods of test  
Fat content, %, min.  3.5 US ISO 2446  
Protein content, %, min.  3.5  US ISO 8968 -1  
Lactose content, %, min.  4.2  US ISO 22662  
Solids Not Fat (SNF), %, min.  8.5  US ISO 6731  
Density at 20 ∘ C, g/mL  1.028 – 1.036  Annex J  
Freezing  point depression,  C  -0.525 – 0.550  US ISO 5764  
Titratable acidity as lactic acid, %  0.1 – 0.2 Annex I  
PH 6.5 – 6.8 Annex C  
 
6 Hygiene  
Raw goat  milk shall be manufactured and handled in a hygienic manner in accordance with US EAS 39. and 
US 163  
6.2 Microbiological requirements  
Raw goat  milk shall comply with limits for micro -organisms specified in Table  2 
Table 2: Microbial limits for raw goat  milk 
Micro -organism  Maximum limit  
cfu/ ml Test method  
Total plate count   2 x 106 US ISO 4833 -1 
Total Colifo rms 5 x104 US ISO 4832  DUS 1548: 2019  
8  © UNBS 201 9 – All rights reserved  
  Somatic cell count  3 x 105 US ISO 13366 -1 
 
7 Contaminants  
7.1 Heavy metals  
When tested in accordance with AOAC 999.10, the level of Lead (Pb) shall not exceed 0. 1 mg/kg.  
8.2 Pesticide residues  
Raw goat milk shall comply with maxim um limits residues set by Codex Alimentarius Commission.  
8.3  Veterinary drug residues  
Raw goat  milk shall comply with maximum tolerable residue limits for antibiotics and other veterinary drugs set 
by Codex Alimentarius Commission  
8.4 Mycotoxins  
When test ed in accordance with  US ISO 14501, the level of aflatoxin M1 shall not exceed 0.50 μg/kg.  
9 Packing and storing  
9.1  Raw goat milk collected from milking shall be kept in clean food grade containers with a good hygienic 
practice before and after use.  
9.2  Raw goat milk from milking shall be immediately delivered to the collection center. In 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 h, it should be frozen a t -18 °C or below provided the delivery time from farm to the 
processing factory is within 15 days.  
9.3  Raw goat milk in the storage tank of the collection centre shall be kept at 4 °C or below and not longer 
than 24 hours prior to delivering to processi ng factory  
10 Transportation  
10.1 The carriage used for delivering raw goat milk from farm to collection centre shall be in a clean and safe 
condition for transportation. In case of non -cooling, the milk shall be immediately delivered within 2 h ours.   
10.2 The carriage or container used for delivery of raw goat milk from collection centre to processing factory 
shall keep milk temperature properly and prevent contamination during transportation  
9 Sampling  
Sampling shall  be done in Accordance to US ISO 707  
  DUS 1548: 2019   
  
 
© UNBS 2019  – All rights reserved   9  
  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 acquired by practice. Organoleptic tests are used in all dair ies 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/withheld for subject ion 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.   
  
Annex B  
(normative)  
  
Determination of insoluble matter (Sediment test)  
B.1 Principle  
The 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 single service strai ners.  
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 the sediment left 
with the prepared standards.  DUS 1548: 2019  
10  © UNBS 201 9 – All rights reserved  
  B.2 Apparatus  
B.2.1  Sediment tester,  with filtering surface 24 mm in diameter  
B.2.2  White lintine cotton discs , 32 mm in diameter, expected filtration area 28 mm in diameter.  
B.2.3   Sampling dipper , of 500 mL capacity for  sampling from milk cans or weighing vats. 
B.2.4   Standard sediment discs , use commercially available standard sediment discs   
B.3 Procedure  
Take a milk sample from well -stirred cans or vats of milk with the sampling dipper. Measure the quantity used 
with reasonable 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 d iscs and record the sediment score.  
B.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 o f the dairy or the milk 
collection depot. For the former, five discs showing 0.1 mg, 0.2 mg, 0.5 mg, 1.0 mg and 2.0 mg may suffice. 
Under rural conditions, discs showing 0.0 mg, 0.5 mg, 2.0 mg, 5.0 mg and 7.0 mg sediment may be more 
convenient to start wit h. 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 unsanitary dairy 
farm practice. However, the lack of sediment is not always indicative of ideal condit ions, since visible 
sediment may be readily removed by straining at the dairy farm.  
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 acidity of milk is only approximate. In normal goat milk the pH ranges from 6.5 - 6.8. The 
value is reduced by the development of acidity. On the other hand, the pH value of milk from a goat suffering 
from mastitis is alkaline in reaction, the value being over 7.0. The pH test is mainly used for the detection of 
abnormal mastitis in milk. The pH of milk may be determined rapidly by using the indicator strips.  DUS 1548: 2019   
  
 
© UNBS 2019  – All rights reserved   11  
  C.2 Indicator strips  
Indicator paper strips or discs are made by soaking strips of absorben t 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 5.2 - 6.8 colour changes from yellow to purple) and bromothymol blu e (pH 
range 6.0 - 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 - 10.5.  
Indicator paper strips shall always be kept in clos ed glass bottles and under dry conditions.  
C.3 Interpretation  
In normal milk the pH is well below 6.9. On an average, goat milk gives a pH of 6.6. Milk of pH greater than 
6.9 should be regarded with suspicion as indication of some diseases of the udder o r of late lactation milk.  
  
Annex D  
(normative)  
  
Clot-on-boiling (C.O.B.) test  
D.1 General  
This is a quick test  to determine developed acidity and the suitability of milk  for processing.  
D.2 Apparatus  
D.2.1  Test-tube , 15.6 cm x 1.9 cm, preferably w ith a mark at 5 mL  
D.2.2  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 almos t horizontal 
position and examine the film of milk or side of the test -tube for any precipitated particles. The formation of 
clots is indicative of a positive test.  DUS 1548: 2019  
12  © UNBS 201 9 – All rights reserved  
  D.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.  
  DUS 1548: 2019   
  
 
© UNBS 2019  – All rights reserved   13  
  Annex E  
(normative)  
  
Alcohol  test  
E.1 Principle  
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 as much as an index o f 
developed acidity. The test aids in detecting abnormal milk, such as colostrum, milk from animals in late 
lactation, milk from animals suffering from mastitis and which the mineral balance has been disturbed.  
E.2 Apparatus  
E.2.1   Test-tubes , 150 mm x 1 9 mm, preferably with graduation marks at 5 mL and 10 mL.  
E.2.2   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 q uantity 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 mi lk sample.  
Milk showing positive is not considered suitable for the manufacture of evaporated milk, which has to be 
sterilized to ensure its keeping quality.  
  DUS 1548: 2019  
14  © UNBS 201 9 – All rights reserved  
  Annex F  
(informative)  
  
Alizarin -alcohol test  
F.1 General  
This test is similar to the alco hol test and the incorporation of alizarin helps to indicate the approximate 
percentage of acidity.  
F.2 Apparatus  
Same apparatus as described in E.2  
F.3 Reagent  
Alizarin solution, 0.2 % in ethyl alcohol (6.8 % by weight or 75 % by volume, density 0.867  5 g/mL at 27 °C)  
F.4 Procedure  
Place 5 mL of milk in a test -tube and add an equal quantity of the alizarin solution. Mix the contents of the 
test-tube by inverting several times. Note the colour of the mixture and 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 as 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 a s follows:  
  
Colour    Size of flakes    Approximate acidity (percent lactic acid)  
Lilac              Up to 0.14  
Pale red              0.4 - 0.17  
Reddish -brown to brown   Small flakes       0.17 - 0.20   
Brownish -yellow    Large flakes       Over 0 .20   
  
If acidity has not developed and yet coagulation occurs, it indicates the presence of rennet producing bacteria 
(sweet curdling).  Milk from animals suffering from mastitis is alkaline in reaction and when mixed with 
alizarinalcohol solution, viol et 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.  
  UGANDA STANDARD  DUS 1548 : 2019  
 
© UNBS 2019  – All rights reserved  23 
 Annex G  
(informa tive)  
  
Ten-minute resazurin test  
G.1 Principle  
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 resor ufin 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 downgraded 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  
G.2.1 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 sterilization, they shall be kept in closed boxes protected from dust.  
G.2.2 Sterilized rubber stoppers , for closing the test tubes. The stoppers are sterilized by immersing in a 
boiling wate r bath for not less than 10 min.  
G.2.3  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 diamete r       7.5 mm - 8.5 mm  
• Graduation          one mark only at 1 -mL level  
• Distance of graduation from tips 140 mm - 180 mm  
• Internal diameter      2.3 mm - 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 
blown 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.  
G.2.4  Sterile 10 mL pipettes , straight -sided, blowout type    
22 © UNBS  2019  – All rights reserved  
 G.2.5 Sampling dippers , 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.  
G.2.6 Pipette case of metal  
G.2.7 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 l evel of the milk in the tubes. The 
interior of the bath shall be completely dark.  
G.2.8 Stop watch  
G.2.9 Hot air oven autoclave or steam -sterilizer  
G.2.10 Wire baskets , for holding test tubes   
G.2.11 Glass marking pencil  
G.2.12 Bunsen burner or spiri t lamp  
G.2.13 Comparator  with standard resazurin disc. The comparator may be provided with artificial daylight 
source of illumination.  
G.2.14 Sterile 50 mL measuring flask or cylinder  
G.2.15 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 wat er. It shall be prepared fresh after every 8 h. When actually not in 
use, keep it in a cool dark place.   
Resazurin powder shall conform to the following requirements:  
a) it shall contain sodium resazurate equivalent to 60 % 
  3 % resazurin;  
b) apart from traces of sodium resocefate, no other dyestuff shall be present;  
c) the remaining part shall consist of sodium carbonate and/or sodium acetate and moisture only;  
d) it shall give a colourless water -clear solution on reduction in al kaline solution; and  
e) at a concentration of 1 to 220 000 in fresh normal mixed goat 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 a nd 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. P lace the tubes in numerical order, with the thumb and fingers of the left hand, taking DUS 1548 : 2019  
© UNBS 2019  – All rights reserved  21 
 care not 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.  
Replace the stopper, by inverting the tube twice in 4 s and 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 j et 
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 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 readin g 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 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 another to record.  
G.5 Precautions  
G.5.1   All testers should be trained to correctly match the colours in the comparator;  
G.5.2   The control and experimental t est tubes shall be of the same type and thickness of glass;  
G.5.3  Control samples used shall be from the same consignment as milk tested to compensate for the natural 
colour of milk;  
G.5.4  Resazurin solution, milk, and milk to which resazurin has been ad ded shall not be exposed to direct 
sunlight in the laboratory;  
G.5.5   The water -bath shall be kept covered during the test; and   
G.5.6  The temperature of the water -bath shall be checked before commencing each batch of tests.  
G.6 Interpretation  
The resu lts shall be interpreted as  follows:  
 Disc reading   Keeping quality  
 4 or higher     Satisfactory  
 3.5 - 1      Doubtful  
 Below 1      Unsatisfactory   
22 © UNBS  2019  – All rights reserved  
 Annex H  
(informative)   
  
Half-hour Methylene Blue 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 solution . Prepare a standard solution of methylen e 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 hours to ensure complete solution.  
Depending o n 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 result s. The solution shall be stored in a sterile glass -stoppered 
ambercoloured 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 solution 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 solution to 
the tubes of milk be introduced into th e 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 G.3 and 
then pour the milk in the test -tube up to the 10 -mL mark.  
While doing this, re move 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 on e 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 wet side of the interior of the tube.  
If this oc curs, discard the pipette immediately. During delivery, hold the tip of the pipette against the dry side 
of the tube about 1 cm - 2 cm above the level of the milk and expel the methylene blue solution by blowing 
with the mouth or by means of a jet in the p ipette. 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 extreme upper end. On no account shall the fingers come into contac t 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 DUS 1548 : 2019  
© UNBS 2019  – All rights reserved  21 
 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 consist of a mixture of milk, preferably from sever al products, so as to 
have an average fat content 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 present in the milk.  
Comparison of the experimental tu bes 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 whole 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  
H.5.1 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.   
H.5.2  It is essen tial 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 reduction of methylene blue.   
H.5.3  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 boiling water.   
H.5.4  The precautions against the contamination of the m ilk 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.   
22 © UNBS  2019  – All rights reserved  
 Annex I  
(normative)   
  
Determination of titratable acidity  
I.1 Principle   
Bacteria that normally develop in raw milk produce more or less of lactic acid. In the acidity test the acid is 
neutralised with 0.1 N Sodium hydroxide and the amount of alkaline is measur ed. From this, the percentage 
of lactic acid can be calculated.   
I.2 Apparatus   
I.2.1 A porcelain dish or small conical flask  
I.2.2 10-mL pipette, graduated  
I.2.3 1-mL pipette  
I.2.4 Burette, 0.1 mL graduations  
I.2.4 Glass rod for stirring the milk  in the dish  
I.2.5 Phenophtalein indicator solution, 0.5 % in 50 % alcohol  
I.2.6 0.1 N Sodium hydroxide solution  
  
Figure 1 ― Apparatus used be acidity test   
I.3 Procedure   
9 mL of the milk measured into the porcelain dish/conical flask. 1 mL phenopt halein is added and then slowly 
from the burette, 0.1 N Sodium hydroxide under continuous mixing, until a faint pink colour appears.   
The number of milllitres of Sodium hydroxide solution divided by 10 expresses the percentage of lactic acid.  DUS 1548 : 2019  
© UNBS 2019  – All rights reserved  21 
 Annex J  
(normative)   
  
Determination of density (Lactometer test)  
J.1 Principle  
Milk has a specific gravity. When it is adulterated with water or other materials are added or both misdeeds 
are committed, the density of milk changes from its normal value to abnorma l. The lactometer test is 
designed to detect the change in density of such adulterated milk.   
J.2 Apparatus  
J.2.1  Measuring cylinder (300 mL – 500 mL)   
J.2.2  Lactometer  
J.3 Procedure   
Mix the milk sample gently and pour it gently into a measuring cylin der (300 mL – 500 mL). Let the 
Lactometer sink slowly into the milk. Read and record the last Lactometer degree (ºL) just above the surface 
of the milk. If the temperature of the milk is different from the calibration temperature (Calibration temperature 
may be = 20 0C ) of the lactometer, calculate the temperature correction. For each ºC above the calibration 
temperature add 0.2ºL; for each ºC below calibration temperature subtract 0.2 ºL from the recorded 
lactometer reading.   
EXAMPLE: Calibration temperat ure of lactometer 20ºC.   
  
Figure 2 ― Equipment used for determination of milk density  
Sample  Milk temperature,  
ºC  Lactometer 
reading, ºL  Correction  True reading,  
ºL  
No. 1  17  30.6  -0.6  30.0  
No. 2  20  30.0  Nil  30.0  
No. 3  23  29.4  +0.6  30.0  
   
22 © UNBS  2019  – All rights reserved  
 For the calculati ons, use lactometer degrees, and for the conversion to density write 1.0 in front of the true 
lactometer reading that is, 1.030 g/mL  
Annex K   
(normative)   
 
Method of Analysis or Identifying Goats Milk from other Dairy Milk  
B.1  Equipment / apparatus  
B.1.1 Polymerase Chain Reaction machine (thermal cycler)  
B.1.2  Water bath  
B.1.3  Micro pipettes  
B.1.4  Vertex  
B.1.5  Micro centrifuge  
B.1.6  Agarose Gel documentation machine  
B.1.7  Conical flask  
B.1.8  Ice cubes  
B.1.9  PCR tube rack  
 B.1.10  Stairoform    
B.1.11 Micro centrifuge tubes   
B.1.12  Timer  
B.1.13  Agarose gel electrophoresis tank  
B.1.14  Analytical balance  
B.1.15  Microwave  
B.1.16  Casting trays and combs  
B.1.17  -20◦C freezers  
B.1.18  -80◦C ultra -freezer  
 
B.2  Reagents   
B.2.1  PCR consumables  
B.2.2 DNA extraction kit (QIA prep spin mini prep form Qiagen, DNeasy Blood and tissue kit from Qiagen 
and Smart Helix First   DNA id from Exvivon) are recommended  
B.2.3  PCR kit (New England bio labs and bioline are recommend ed kits for convectional PCR  DUS 1548 : 2019  
© UNBS 2019  – All rights reserved  21 
 B.2.4 Agarose powder  
B.2.5  Absolute ethanol  
B.2.6  Nuclease free water  
B.2.7  Primers for goat, cow, sheep, camel, buffalo and the expected source of the dairy animal to mixed 
with the goat’s milk. (Primers should target the 12S rRNA region)   
B.2.8  Molecular marker (depends on the expected band size of the amplicon)  
B.2.9  TAE buffer (1X)   
B.2.10  Gel Red dye  
 
B.3  Procedure  
Design primers or commercially acquire them for goat , cow ,sheep , camel, buffalo and any other dairy animal 
species you expect its mi lk to be mixed with the goat milk,. The designed primer should target the 
mitochondrial cytochrome b gene (12S rRNA). The DNA extraction is done from milk samples following the 
extraction protoc ol from the above mentioned recommended DNA extraction kits.  The PCR reaction mixture 
is set up following the PCR mini protocol that comes along with PCR kit. The reaction mixture is then 
transferred to the PCR machine (thermal cycler) and the conditions are set following the conditions on the 
PCR kit protocol. After the PCR, the amplicons are then loaded on the agarose gel stained with gel Red of a 
known percentage and placed in the gel electrophoresis tank containing 1X TAE (Tris Acetate EDTA) buffer 
and the tank is   set at 100V, 300MA for 1 hour. Then the gel is then transferred to the gel documentation 
machine to visualise the bands of interest using the UV light lamp fixed in the gel documentation machine. 
The presence of the expected band size of goa t only qualifies the purity and quality of the goat’s milk. But the 
presence of other expected band size of other dairy milk animals signifies the presence of other dairy milk 
from other species of dairy animal and this disqualifies the purity and quality of the goat’s milk.   
22 © UNBS  2019  – All rights reserved  
 Bibliography  
[1]  
 DUS 2145 : 2019  
© UNBS 2019  – All rights reserved  23 
 Certification marking  
Products that conform to Uganda standards may be marked with Uganda National Bureau of Standards 
(UNBS) Certification Mark shown in the figure below.  
The use of the UNBS Certification Mark is g overned 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 National Bureau of Standards and in conjunction with the relevant Uganda Standard. Th e 
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 licensing may be obtained from the Director, Uganda 
National Bureau of Standards.  
 
 DUS 1548 : 2019    
 
ICS 60.100.01  
Price based on nn pages  
© UNBS 2019 – All rights reserved