KENYA STANDARD              DKS 2147 : 2007 
ICS 67.100  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Raw whole goat milk  — Specification  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
© KEBS 20 16            Second  Edition 2016 
 
 
 DKS 2147 : 2016 
     KEBS 2007  — All rights reserved  ii TECHNICAL COMMITTEE REPRESENTATION  
 
The following organizations were represent ed on the Technical Committee:  
 
Kenya Dairy Board - Chair  
Ministry of Health — Food Safety Unit  
Ministry of Agriculture, Livestock and Fisheries — Directorate of Livestock Resources and Market Development  
Ministry of Agriculture, Livestock & Fisheries - Directorate of Veterinary Services and Livestock Production  
Egerton University — Department of Dairy and Food Science Technology  
Government Chemist’s Department  
National Public Health Laboratory Services  
Kenya Industrial Research and Development Institute (KIRDI)  
Consumer Information Network  
New Kenya Cooperative Creameries Limited (NKCC)  
Brookside Dairy Ltd.  
Eldoville Dairies Limited  
Githunguri Dairy  
Happy Cow Ltd  
Sameer Agriculture and Livestock (K) Limited  
Kibidav Ltd (TOGGS)  
Kenya Bureau of Standards  — Secretariat  
 
 
 
 
 
 
 
 
 
 
 
REVISION OF KENYA STANDARDS  
 
In order to keep abreast with the progress in the industry, Kenya standards shall be regularly reviewed. 
Suggestions for improvement of published standards are welcome and should be addressed to the Ma naging 
Director, Kenya Bureau of Standards.  
 
 
 
 
 
 
©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, copyr ight subsists in 
all Kenya Standards and except  as provided under Section 26 of this Act, no Kenya Standard produced by Kenya Bureau of Standards 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 . 
 
 
 
  
KEBS 2007  — All right s reserved  iii  
 
 
 
KENYA STANDARD                                      DKS 2147 : 2016 
                        ICS 67.100  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Raw whole goat milk  — Specification  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
KENYA BUREAU OF STANDARDS (KEBS)  
 
Head Office:  P.O. Box 54974, Nairobi -0020 0, 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) 229448     Fax: (+254 057) 21814  DKS 2147 : 2016 
     KEBS 2007  — All rights reserved  iv  
 
 
 
Foreword  
 
This Kenya standard w as prepared by the Technical Committee on Milk and Milk Products  under the guidance of 
the Standards Project Committee and it is in accordance with the procedures of the Kenya Bureau of Standards . 
 
This standard only covers  raw whole goat’s milk.  
 
This sta ndard covers the quality, microbiological, contaminants and labeling requirements of raw whole goat  
milk.  
 
This standard has also provided a method for determining adulteration of goat’s milk with cow’s milk  
 
The standard intends to promote the production  of safe and high quality goat  milk.  
KEBS 2007  — All rights reserved  1 KENYA STANDARD                             DKS 2147 : 2016 
 
Raw whole goat milk — Specification  
 
 
1 Scope  
 
This Kenya Standard specifi es the requirements and methods of  sampling and test for raw whole goat’s milk.  
 
2 Normative references  
 
The following publications contain provisions which, through reference in this text, constitute provisions of this 
standard . At the time of publi cation, the edition indicated was valid. For undated references, the latest edition of 
the normative document referred to applies.  
 
AOAC 922.08, Hypochlorite and chloramins in milk, colorimetric method  
AOAC 942.17, Arsenic in foods Molybdenum blue method  
AOAC 947.05; Acidity of milk, trimetric method  
AOAC 960.27, preservatives in milk  
AOAC 962 .16, Beta-lactam Antibiotics in milk  
AOAC 972.17 Official method; copper in milk and milk products, colometric method  
AOAC 980.21, 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  
AOAC 960.40, Official method; Copper in, milk and milk products - Colometric method  
AOAC 942.17, Arsenic in foods molybdenum blue method  
AOAC 970.52; Organochlorine and organophosohorous pesticides resi dues in milk  
AOAC 974.17, Aflatoxin M1 in milk and cheese -thin layer chromatographic methods  
969.19; moisture in cheese, method iii (Distilation method)  
AOAC 982.14, 15, 16, 17 and18, Beta -lactam Antibiotics in milk  
AOAC 962.14, Beta -lactam Antibiotics in milk 
CAC/MRL 1; Maximum Residue Limits (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 contaminants and toxins in foods  
KS ISO 1211:2010 (IDF1:2010) ; Milk -- Determination of fat content -- Gravimetric method (Referenc e method)  
KS ISO 2446, Milk — Determination of fat content (Routine method)  
KS ISO 3890 -1:2009 (IDF 75 -1:2009) ; Milk and milk products -- Determination of re sidues of organochlorine 
compounds (pesticides) -- Part 1: General considerations and extraction methods  
KS ISO 3890 -2:2009 (IDF 75 -2:2009) ; Milk and milk pr oducts -- Determination of residues of organochlorine 
compounds (pesticides) -- Part 2: Test methods for crude extract purification and confirmation  
 
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  
 DKS 2147 : 2016 
  KEBS 20 16 — All rights reserved  2 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 cryoscope 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, Milk, 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  
 
  
 
2 Definition s 
 
For the purposes of this standard, the following definition shall apply.  
 
2.1 
raw whole milk  
isthe normal, clean and fresh secretion obtained by practically emptying the udder of a healthy goat, properly fed 
and kept, but excluding that got  during the first seven days after kidding and free from colostrum  
 
3 Principal compositional requirements  
 
3.1 Chemical  
 
3.1.1  When tested in accordance with KS ISO 2446 ; raw whole milk shall contain not less than 3.5 % milk fat 
and not less than 8.5 % mi lk solids not fat.  
 
3.1.2  It shall not contain added water, preservatives, or other added substances, nor shall any proportion of a 
natural constituent be removed  when tested in accordance to AOAC 960.27, preservatives in milk  
 
3.1.3     Adulteration of go at’s milk with cow’s milk  
This practice shall not be allowed.  
Adulteration of goat milk with Cow’s milk shall be tested in accordance to the RIDA Quick CIS  
Test method given in Annex A  
 
3.1.4      Hypochlorite’s and chloramines in goat’s milk 
 
Pasteurized  goat milk shall contain no Hypochlorite’s and chloramines when tested in accordance  to AOAC 
922.08  
 
 
3.1.5 Density of the milk at 20 0C shall be within the following range:  
 
                      1.028 g/mL — 1.032 g/mL  
 
 
3.1.6 When tested according to the KS ISO 5764,  the freezing point depression of milk shall be a -0.48 0C — 
0.568  0C; Indicating  the abs ence of added water . 
 
 
 
3.1.7 Raw milk shall have a pH of 6.6 — 6.8. DKS 2147 : 2016 
KEBS 20 16— All rights reserved  3  
3.1.8 The milk shall comply with the rapid tests described in Annexes A — H. 
 
Table 2 — Physico -chemical requirements  for raw whole goat  milk 
 
SL No  Parameter  Requirement  Test method  
i) pH  6.5 - 6.8   KS ISO 5546  
ii) Total acidity  (expressed as 
% of lactic acid),max  
 0.20 KS ISO/TS 11869  
 
iii) Density of the milk at 20 0C 1.028 g/ mL - 1.032 
g/mL     KS ISO 5764  
iv) freezing poi nt depression of 
milk (to i ndicat e the abs ence 
of added water ) ±0.480 0C to ±0.568 0C AOAC 961.07/  
KS ISO 5764  
 
 
 
4 Microbiological limits  
 
4.1 Total plate count   
 
The plate shall be incubated for 48 h at 32 0C. The counts shall be taken and graded as follows : 
 
Table 1 — Microbiological load in raw goat whole milk  
 
 
 
 
 
 
 
 
4.2 Coliform plate count   
 
The plate shall be incubated for 24 h at 37 0C. The counts shall be taken and graded as follows:  
 
Table 2 — Coliform counts in raw whole milk  
 
Grade  
 Counts per mL  
i) 0 – 1 000  
 
ii) 1 001 – 40 000  
 
 
Pathogens  
Microbes  
 Limits  Test method  
S. aureus  
 Nil KS ISO 6888 -1 
E. coli  
 Nil KS ISO 4833  
L. monocytogenes  
 Nil KS ISO 4833  Grade  
 Bacterial counts per mL  
i) 0 – 400 000  
 
ii) 400 001 – 1 000 000  
 DKS 2147 : 2016 
  KEBS 20 16 — All rights reserved  4 Salmonella spp  
 Nil KS ISO 6785  
 
5 Contaminants  
 
The products covered by this s tandard 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 pasteurized goat milk  shall be as given in Table 4 . 
 
 
Table 4  — Limits for heavy meta l contaminants pasteurized goat  milk 
 
 
SL No   
Heavy metal   
MRL  
(max.)  
Test metho d 
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 999.1 0 
vii) Cadmium as Cd,  
 1.5 mg/kg  AOAC 999.10  
 
viii) Iron (fe),  
 0.5 mg/kg  KS ISO 6732  
 
 
 
5.2       Mycotoxin residues  
 
Pasteurized goat milk shall not have more than 0.015  ppb aflatoxin M1 content when teste d according to KS ISO 
14501 or AOAC 980.21 . 
 
5.3       Total antibiotic residues  
 
Pasteurized goat milk shall not have more than 10.0 ppb total 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 L aws of Kenya and the CODEX guidance.  
The milk shall not contain any antibiotics.  
 
5.4           Veterinary drug residues    DKS 2147 : 2016 
KEBS 20 16— All rights reserved  5 In addition to the  maximum veterinary drug residue  limits in table 6 below; t he products covered by the 
provisions of this standard shall conform to those maximum limits for veterinary drug residue limits established 
by the Codex Alimentarius Commission for these products in codex Stan 193;  
 
When analyzed by the appropriate approv ed methods  as given in Table 5 , pasteurized goat milk shall not 
contain any veterinary drug residues .      
 
Table 5 — Maximum veterinary drug residue limits for pasteurized goat milk  
 
S/N Parameter  Requirements/ 
MRL  Test method  
i) ChloramPhenical  ND AOAC 972.17  
ii) Nitrofunas  (including 
metabolites)  ND AOAC 960.63  
iii) Ronidazole  ND AOAC 969.56  
iv) Metronidazole  ND AOAC 991.17  
v) Fenbendazole  100 ppb AOAC 991.17  
vi) Albendazole  100 ppb AOAC 991.17  
vii) Phenylbutazone  ND  AOAC 991.17  
 
 
 
5.5 Pesticide residues  
 
In addition to the maximum  pesticide residue  limits in table 6 below; the products covered by the provisions of 
this standard shall conform to those maximum limits for pesticide  residue limits established by the Codex 
Alimentarius Commissi on for these products in codex Stan 193;  
 
 
Pasteurized goat milk shall not contain pesticide residues in excess of the residue limits  given in T able 6 . 
 
Table 6 — Maximum pesticide residue limits for pasteurized goat milk  
 
SL 
No Parameter  Requirement  Test method  
i) ORGANOCHLORINE Group  0.01 ppm  KS ISO 3890  
ii) ORGANOPHOSPHOROUS 
Group  0.01 ppm  AOAC 960.40  
 
 
 
 
6 HYGIENE   
 
6.1 It is recommended that the products covered by the provisions of this standard be prepared and handled 
in accordance with the appropria te sections of KS 1552:2016  and other relevant Kenya standards and DKS 2147 : 2016 
  KEBS 20 16 — All rights reserved  6 regulations.  The products should comply with any microbiological criteria established in accordance with KS 
CAC/GL 21 .  
 
6.2 It shall be transported in sanitized containers. The containers shall be made of approved food grade 
materials and shall comply with the relevant Kenya standards. Where no immediate processing or marketing is 
undertaken after milking, the milk shall be rapidly cooled to 4 C   
 
 
 
 
 
 
3) Guide to maximum pesticide limits in products . 
 
4) Code of hygienic practice for milk and milk and milk products.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 DKS 2147 : 2016 
KEBS 20 16— All rights reserved  7  
ANNEX A  
(Normative)  
 
A.1 Determination of goat’s milk adulteration with cow’s  milk using  RIDA Quick CIS  Test 
 
A.1.1 Principle  
RIDA Quick C IS Test  is an immunochromatographic test for the detection  of cow’s milk in milk or cheese of other 
species (sheep and goat).  
The detection of an addition cow’s milk to sheep and goats milk or to sheep and goats cheese is carried out by 
determining bovine igG (antibody class), which is a component of cow’s milk. Adulteration with cow’s milk in 
ultra-heated products cannot be detected since the antibodies are destroyed by ultra -high heating.  
The detection of cow’s milk in ultra -high heated products can be do ne using RIDA Screen casein test 
adulteration  
 
A.1.2 Apparatus  and Reagents  
The test is strip format. The apparatus and reagents include;  
Reaction strips  
Pipette  
Test tubes  
10ml buffer  
 
A.1.3 Sample Preparation  
Milk samples are used directly in the test w ithout preliminary treatment and the result can be read off after ten 
minutes  
  
A.1.4 Detection Limit  
RIDA  QUICK CIS test is capable to detect adulterations or mixtures up to 0.5 % cow’s milk in sheep and goats 
milk. A positive result indicates that the sa mple has a cow milk content of 0.5 % or more.  
 
 
 
 
 
 
 
Annex B 
(normative)  
 
Organoleptic test and temperature  
 
B.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 of accuracy.  
 
B.2 Procedure to be adopted on the receiving platform  
 
B.2.1 Foreign matter   
 DKS 2147 : 2016 
  KEBS 20 16 — All rights reserved  8 Presence of the foreign matter such as pieces of dung, hair or any other foreign material should be checked.  
 
B.2.2 Odour   
 
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.  
 
B.2.3 Colour   
 
Obse rve the colour of the milk. If abnormal in colour, it should be held over for subjection to confirmatory tests.  
 
B.2.4 Flavour/ Taints   
 
Examine the milk for the following taints:  
 
B.2.4.1  Those due to developed acidity. This is the most important factor to  be examined when grading milk by 
organoleptic test.  
 
B.2.4.2  Those due to feed, or exposure of milk to air or contamination from containers.  
 
 
 
 
 
 
 
 
Annex  C 
(normative)  
 
Determination of insoluble matter  
 
C.1 Sediment test  
 
C.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 single service strainers.  
 
The sediment test represents a simple, rapid and quantitative measure o f indicating the cleanliness of milk with 
respect to visible dirt.  
 
The test is carried out by allowing a measured quantity of milk to pass through a fixed area of a filter disc and 
comparing the sediment left with the prepared standards.  
 
C.1.2 Apparatus  
 
C.1.2.1  Sediment tester , with filtering surface 24 mm in diameter.  
 
C.1.2.2  White lintine cotton discs , 32 mm in diameter, expected filtration area 28 mm in diameter.  
 
C.1.2.3  Sampling dipper , of 500 mL capacity for sampling from milk cans or weighing vat s. 
 
C.1.2.4  Sieves , two, one coarse corresponding to 425 -micron sieves.  
 
C.1.2.5  Sediment disc ratings , showing 0.0 mg, 0.2 mg, 0.5 mg, 1.0 mg, 2.0 mg, 3.0 mg sediment or higher 
concentration as required per 500 mL of milk.  
 
C.1.3 Preparation of standard s ediment discs   DKS 2147 : 2016 
KEBS 20 16— All rights reserved  9  
Since sediment encountered in different localities may vary in composition, density, colour and other physical 
characteristics, thus giving rise to variations in the appearance, sediment discs shall be prepared as follows:  
 
Make a uniform mixture of oven -dried (100 0C) materials which meet the following screening specifications:  
 
i) cow dung passing through 53 parts fine sieve;  
 
ii) cow dung passing through 10 parts coarse sieve but retained on the fine one;  
 
iii) garden soil passing throug h 27 parts sieve;  
 
iv) charcoal passing through the fine 8 parts sieve;  
 
v) charcoal passing through the coarse sieve but retained on the fine one.  
 
Total: 100 parts.  
 
Accurately weigh 0.1 g of the above mixture and transfer to a 100 mL flask using 50 % su gar solution to wash all 
fine particles down into the flask. Make the volume up to the mark with more of the sugar solution after most of 
fine particles have been wetted by shaking the half -filled flask thoroughly several times. After the volume is made 
up to the mark, shake the contents of the flask vigorously every 5 min for sufficient time (for 30 min to one hour) 
to saturate particles thoroughly.  
 
When particles have been thoroughly wetted, it will be noted that the sugar solution will hold them evenly in 
suspension and the mixture is ready for use in making the standard discs.  
 
On the basis of 0.1 g per 1 000 mL, 10 mL of the sugar solution contains 1 mg of the sediment. Make test discs 
with one of the usual sediment testers using varying volumes of the  sediment suspension.  
 
After forcing the milk through the disc, run through a small quantity of filtered skimmed milk to obtain a more 
even distribution of the sediment on the disc.  
 
Remove the discs from the tester, mount them permanently by spraying with  a strong disinfectant, such as 
corrosive sublimate.  Below each mounted standard disc on paper, note the quality of dried material that the dirt 
or filth on the disc represents.  
 
C.1.4 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 discs and record the sediment score.  
 
C.1.5 Interpretations   
 
For the purpose of comparisons, it is convenient to use about five prepared standard discs so as to classify the 
milk with respect to its se diment content in accordance with the specific requirement of 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 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, pieces 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 in sanitary 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.  DKS 2147 : 2016 
  KEBS 20 16 — All rights reserved  10  
 
 
 
 
 
 Annex D  
 (normative)  
 
Determination of pH  
 
D.1 General  
 
The pH value or hydrogen ion concentration giv es a measure of the true acidity of milk. The relationship 
between pH and acidity of milk is only approximate. In normal 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 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.  
 
D.2 Indicator strips  
 
Indica tor 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  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. Booth 
narrow and wide range ready -made indicator papers are available over the pH r ange 2.0 to 10.5.  
 
NOTE   Indicator paper strips shall always be kept in closed glass bottles and dry conditions.  
 
D.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 over 6.9 should 
be regard ed with suspicion as indication of some diseases of the udder or of late lactation milk.  
 
 
 
 
 
 
Annex E 
(normative)  
 
Clot on boiling (COB) test  
 
 
E.1 General  
 
This is a quick test to determine developed acidity and the suitability of milk for processing.  
 
E.2 Apparatus  
 
D.2.1  Test-tube , 15.6 cm x 1.9 cm, preferably with a mark at 5 mL.  
 
D.2.2  Water -bath  DKS 2147 : 2016 
KEBS 20 16— All rights reserved  11  
E.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 the test -tube for any precipitated particles. The formation of clots are indicative 
of a positive test.  
 
E.4 Interpretation  
 
The prin cipal features of the boiling test are speed and definiteness of results.  Milk either remains unchanged or 
coagulates. Milk which gives a positive COB test has an acidity generally above 0.17 % (as lactic acid) and is not 
suitable for distribution as liqu id milk or for processing.  
 
 
 
 
 
 
 
Annex F 
(normative)  
 
Alcohol test  
 
F.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 colostrum, milk from animals in late 
lactation, milk from animals suffering from mastitis and milk in which the mineral bal ance has been disturbed.  
 
F.2 Apparatus  
 
F.2.1 Test-tubes , 150 mm x 19 mm, preferably with graduation marks at 5 mL and 10 mL/alcohol gun.  
 
F.2.2 Measure for alcohol , for 5 mL.  
 
F.3 Reagent  
 
F.3.1 Ethyl alcohol , 62 % by weight or 75 % by volume (density 0. 867 5 g/mL at 27 0C). 
 
F.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 . 
 
F.5 Interpretation  
 
A negative test indicates low acidity and good heat stability of milk sample.  
 DKS 2147 : 2016 
  KEBS 20 16 — All rights reserved  12 Milk showing positive is not considered suitable for the manufacture of evaporated milk which has to be sterilized 
to ensure its keeping quality.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Annex G 
(normative)  
 
Alizarin -alcohol test  
 
G.1 General  
 
This test is similar to the alcohol test and the incorporation of alizarin helps to indicate the approximate 
percentage of acidity.  
 
GF.2 Apparatus  
 
G.2.1 Test tubes , 150 mm x 19 mm, prefera bly with graduation marks at 5 mL and 10 mL.  
 
F.2.2  Measure for alcohol, for 5 mL.  
 
G.3 Reagent  
 
F.3.1  Alizarin solution   
 
0.2 % in ethyl alcohol (6.8 % by weight or 75 % by volume, density 0.867 5 g/mL at 27 0C). 
 
G.4 Procedure  
 
Place 5 mL of milk in a te st-tube and add an equal quantity of the alizarin solution. Mix the contents of the te st-
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.  
 
G.5 Interpre tation  
 
G.5.1 The general interpretation of the results is as indicated for the alcohol test (see Clause 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 (% lactic acid)  DKS 2147 : 2016 
KEBS 20 16— All rights reserved  13 Lilac           -                                                              up to 0.14  
 
Pale red            -                                                              0.14 to 0.17  
 
Reddish -brow n to brown     Small flakes                                                  0.17 to 0.20  
 
Brownish -yellow                  Large flakes                                                  over 0.20  
 
G.5.2 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 
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.  
 
 
 
 
 
 
 
Annex H 
(normative)  
 
Ten-minute resazurin test  
 
H.1 General  
 
This test provide s 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 to the colourless dihydroresorufin. The first stage of reduction 
or colour change from blue to pink is easily brought about so that the fairly quality of milk is assessed in much 
shorter time.  Taking advantage of the two -stage reduction, several procedures h ave been proposed for reading 
the end point of resazurin test.  
 
With fresh milk, the observed change in resazurin reduction is due to the bacterial 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 a s a platform test for detecting milk of poor keeping quality and shall be carried out on 
samples collected for bacteriological analysis.  
 
H.2 Apparatus  
 
H.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.  
 
H.2.2 Sterilized rubber stoppers , for closing the test -tubes. The stoppers are sterilized by immersing in a 
boiling water -bath for not less tha n 10 min.  
 
H.2.3 Sterile 1 mL pipettes , straight -sided, blow -out delivery pipettes for measuring the dye solution (see 
Clause G.3) shall preferably comply with the following specifications:  
 
Overall length      300 mm  
 
External diameter     7.5 mm to 8.5 mm  
 DKS 2147 : 2016 
  KEBS 20 16 — All rights reserved  14 Graduation      one mark only at 1 mL level  
 
Distance of graduation from tip    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 0C when the contents are blown out with the 
tip tou ching the side of the vessel, 3 s 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 1.98 mL and 1.02 mL.  
 
H.2.4 Sterile 10 mL pipettes , straight -sided, 1.98 mL and blow -out type .  
 
H.2.5 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.  
 
H.2.6 Pipette case , of metal.  
 
H.2.7 Water-bath , maintained at 37.5 0C ± 0.5 0C, 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 s hall be maintained above the level of the milk in the tubes. The interior 
of the bath shall be completely dark.  
 
H.2.8 Stop -watch  
 
H.2.9 Hot air ove n autoclave or steam -sterilizer  
 
H.2.10  Wire baskets , for holding test -tubes  
 
G.2.11  Glass marking pencil  
 
H.2.12  Bunsen burner or spiri t lamp  
 
H.2.13  Comparator with standard resazurin disc , the comparator may be provided with artificial daylight 
source of illumination.  
 
H.2.14  Sterile 50 mL , measuring flask or cylinder.  
 
H.2.15  Glass distiller , for preparing d istilled water.  
 
H.3 Reagent  
 
G.3.1  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 s olution 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 equivale nt to 60 % ± 3 % 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 only;  
 
iv) it shall give a colourless water -clear sol ution on reduction in alkaline solution;  
 
v) 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.  DKS 2147 : 2016 
KEBS 20 16— All rights reserved  15  
H.4 Procedure  
 
Start the test as soon as possible after a group of s amples 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 t est 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 m L of the resazurin solution with a sterile pipette. Insert the pipette about half an 
inch int o the mouth of the tube and expel the solution by blowing.  
 
Replace the stopper, mix 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 no te 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 ± 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 do wn on the two apartures. 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 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.  
 
H.5 Precautions  
 
The following precautions are necessary to get consistent results:  
  
i) all testers should be tra ined to correctly match the colours in the comparator;  
 
ii) the control and experimental test -tubes shall be of the same type and thickness of glass;  
 
iii) control samples used shall be from the same consignment as milk tested to compensate for the natural  
colour of milk;  
 
iv) resazurin solution, milk, and milk to which resazurin has been added s hall not be exposed to direct 
sunlight in the laboratory;  
 
v) the water -bath shall be kept covered during the test;  
. 
vi) the temperature of the water -bath shall be  checked before commencing each batch of tests.  
 
H.6 Interpretation  
 
The results shall be interpreted as follows:  
 
Disc reading      Keeping quality  
 
5 or higher      Satisfactory  
 
3.5 to 1       Doubtful  
 
0.5 to 0       Unsatisfactory  DKS 2147 : 2016 
  KEBS 20 16 — All rights reserved  16  
 
 
 
 
Annex I 
(normative)  
 
Half-hour methylene blue redu ction (MBR) test  
 
I.1 General  
 
The length of time taken by milk to decolourize methylene blue is a fairly good measure of its bacterial content 
and hence its sanitary and keeping quality.  
 
I.2 Apparatus  
   
Same as in Clause G .2. 
 
I.3 Reagent  
 
I.3.1 Methylene blue solution   
 
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 hours 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 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 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.  
 
I.4 Procedure  
 
Thoroughly mix the sample of the milk by inverting and shaking the sample bottle as describe d in Clause G.3 
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 con tact with any of the 
milk in the tube or with the wet 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 t he milk and expel the methylene blue solution by blowing 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 
extreme upper end. On 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 who le DKS 2147 : 2016 
KEBS 20 16— All rights reserved  17 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 met hylene blue solution.  
 
The milk for the control tubes shall consist of a moisture of milk, preferably from several products, so as to have 
an average fat content and col our.  Fit the control tubes at i) and ii) with stoppers and immerse for 3 min in 
boilin g water in order to destroy the natural reducing system present in the milk.  
 
Comparison of the experimental tubes with c ontrol tube ii) will show when decolourisation begins an d 
comparison with control tube i) will show when it is complete.  
 
Inspect the t ube after 30 min.  Regard the milk as decolourized when the whole column of milk is completely 
decolourized or is completely decolorized 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 de -colourization is observed. Where a tube is found not to be decolourized within 30 min, the sample 
conforms to the test.  
 
I.5 Precautions  
 
The following precautions shall be taken:  
 
i) 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;  
 
ii) it is essential that the interior of the water bath during the progress of the tests shall be completely dark 
since su nlight, diffused daylight and even artificial light catalyze the reduction of methylene blue;  
 
iii) 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 of rubber stoppers immersed in 
a suitable vessel of boiling water;  
 
iv) the precautions against the contamination of the milk sample described in the method for carrying out 
the test shall be carefully observed.  
 
I.6 Interpretation  
 
The samples, which show complete decolourization of blue colour on incubation for 30 min or less, shall not be 
suitable for acceptance.