FOR INTERNAL USE ONLY 
COMMITTEE DRAFT DRAFT UGANDA STANDARD  
  DUS DEAS  997 
First  Edition  
2019-mm-dd 
 
 Reference number  
DUS DEAS  997: 2019 
© UNBS 2019 
   
Baker’s yeast  — Specification  
 
 FOR INTERNAL USE ONLY 
COMMITTEE DRAFTDUS DEAS 997: 2019 
ii                © UNBS  2019 - 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 application  
© 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 UNBS. 
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: +256 417 333 250/1/2 
Fax: +256 414 286 123 
E-mail: info@unbs.go.ug  
Web: www.unbs.go.ug  
 FOR INTERNAL USE ONLY 
COMMITTEE DRAFTDUS DEAS 997: 2019 
© UNBS  2019 - All rights reserved                iii National 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 World 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 representatives of 
consumers, traders, academicians, manufacturers, 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, DUS DEAS 997: 2019 , Baker’s yeast  — Specification , is identical with and has 
been reproduced from an East African Standard, DEAS 997: 2019, Baker’s yeast  — Specification , and is 
being proposed for adoption as a Uganda Standard. 
The committee responsible for this document is Technical Committee UNBS/TC 2,  Food and agriculture.  
Wherever the words, “ East African Standard " appear, they should be replaced by "Uganda Standard." 
 
  DEAS 997: 2019  
ICS 67.220.20  
 
© EAC 2019                                                                                                                               First Edition 2019   
 DRAFT EAST AFRICAN STANDARD  
Baker’s yeast  — Specification  
EAST AFRICAN COMMUNITY  DEAS  997: 2019  
ii © EAC  2019  – All rights reserved  
 Copyright notice  
This EAC document is copyright -protected by EAC. While the reproduction of this document by 
participants in the EAC standards development process is permitte d without prior permission from EAC, 
neither this document nor any extract from it may be reproduced, stored or transmitted in any form for 
any other purpose without prior written permission from EAC.  
Requests for permission to reproduce this document for the purpose of selling it should be addressed 
as shown below or to EAC’s member body in the country of the requester:  
© East African Community  2019  — All rights reserved  
East African Community   
P.O. Box 1096 , 
Arusha  
Tanzania  
Tel: + 255 27 2 162100  
Fax: + 255 27 2162190  
E-mail: eac@eachq.org  
       Web: www.eac -quality.net  
Reproduction for sales purposes may be subject to royalty payments or a licensing agreement.  
Violators may be prosecuted . DEAS 997: 2019  
© EAC 2019  – All rights reserved  iii 
 Contents  Page 
1 Scope  ................................ ................................ ................................ ................................ ......................  1 
2 Normative references  ................................ ................................ ................................ ............................  1 
3 Terms and definitions  ................................ ................................ ................................ ...........................  2 
4 Types of baker’s yeast  ................................ ................................ ................................ ..........................  2 
5 Requirements  ................................ ................................ ................................ ................................ .........  2 
5.1 General requirements  ................................ ................................ ................................ ...........................  2 
5.2 Specific requirements  ................................ ................................ ................................ ...........................  3 
5.2.1  Fresh Baker’s Yeast (FBY)  ................................ ................................ ................................ ...................  3 
6 Hygiene  ................................ ................................ ................................ ................................ ...................  3 
6.1 Microbiological requirements  ................................ ................................ ................................ ..............  4 
7 Packaging  ................................ ................................ ................................ ................................ ...............  4 
8 Weights and measures  ................................ ................................ ................................ .........................  4 
9 Labelling  ................................ ................................ ................................ ................................ .................  4 
 DEAS  997: 2019  
iv © EAC  2019  – All rights reserved  
 Foreword  
Development of the East African Standards has been necessitated by the need for harmonizing requirements 
governing quality of products and services in the East African Community. It is envisaged th at through 
harmonized standardization, trade barriers that are encountered when goods and services are exchanged 
within  the Community will be removed.  
The Community has established an East African Standards Committee  (EASC)  mandated to develop and 
issue Ea st African Standards  (EAS) . The Committee is composed of representatives of the National 
Standards Bodies in Partner States, together with the representatives from the public and private sector 
organizations  in the community .  
East African Standards are de veloped through  Technical Committees that are representative of key 
stakeholders including government, academia, consumer groups, private sector and other interested parties. 
Draft East African Standards are circulated to stakeholders through the National Standards Bodies in the 
Partner States. The comments received are discussed and incorporated before finalization of standards, in 
accordance with the Principles and procedures for develop ment of East African Standards . 
East African Standards are subject to  review, to keep pace with technological advances. Users of the East 
African Standards are therefore expected to ensure that they always have the latest versions of the standards 
they are implementing .  
The committee responsible  for this document is Techni cal Committee EASC/TC 005, Food additives . 
Attention is drawn to the possibility that some of the elements of this document may be subject of patent 
rights. EAC shall not be held responsible for identifying any or all such patent rights.  DEAS 997: 2019  
© EAC 2019  – All rights reserved  v 
 Introduction  
Strains of yeast, essential for regulating the fermentation and aromatic activity of fermented doughs are known 
as baker’s yeast. These yeasts play three major roles:  
 increasing the volume of dough by producing carbon dioxide via alcoholic fermentation of suga rs 
present in the dough;  
 bringing about change in the structure and texture of the dough because of the carbon dioxide 
bubbles; and  
 adding flavour to baked product.  
In the EAC , different types of baker's yeast are available, most of which are imported, for  both commercial 
bakeries and home use.  
This D raft Standard has been  developed to ensure the safety and quality of baker’s yeast produced and/ or 
traded in the EAC . 
 DRAFT EAST AFRICAN STANDARD  DEAS 997: 2019  
 
© EAC 2019  – All rights reserved  1 
 Baker’s yeast — Specification  
1 Scope  
This Draft East African Standard specifies require ments, sampling and test methods for baker's yeast . 
2 Normative references  
The following documents are referred to in the text in such a way that 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.  
CODEX STAN 107 , General standard for the labelling of food additives when sold as such  
CODEX STAN 192 , General standard for food addit ives 
CAC/GL 50 , General guidelines on sampling   
EAS 1, Wheat flour – Specification  
ISO 4832 , Microbiology of food and animal feeding stuffs — Horizontal method for the enumeration of 
coliforms — Colony -count technique  
ISO 6579 -1, Microbiology of the food c hain — Horizontal method for the detection, enumeration and 
serotyping of Salmonella  — Part 1: Detection of Salmonella spp.  
ISO/TS 6579 -2, Microbiology of food and animal feed — Horizontal method for the detection, enumeration and 
serotyping of Salmonella — Part 2: Enumeration by a miniaturized most probable number technique  
ISO 6888 -1, Microbiology of food and animal feeding stuffs — Horizontal method for the enumeration of 
coagulase -positive staphylococci (Staphylococcus aureus and other species) — Part 1 : Technique using 
Baird -Parker agar medium   
ISO 6888 -2, Microbiology of food and animal feeding stuffs — Horizontal method for the enumeration of 
coagulase -positive staphylococci (Staphylococcus aureus and other species) — Part 2: Technique using 
rabbit pl asma fibrinogen agar medium  
ISO 6888 -3, Microbiology of food and animal feeding stuffs — Horizontal method for the enumeration of 
coagulase -positive staphylococci (Staphylococcus aureus and other species) — Part 3: Detection and MPN 
technique for low numbe rs 
ISO 7251 , Microbiology of food and animal feeding stuffs — Horizontal method for the detection and 
enumeration of presumptive Escherichia coli — Most probable number technique  
EAS 39, Hygiene in the food and drink manufacturing industry — Code of practi ce 
ISO 15914 , Animal feeding stuffs — Enzymatic  determination of total starch content  
2 © EAC  2019  – All rights reserved  
 3 Terms and definitions  
For the purposes of this document, the following terms and definitions apply.  
ISO and IEC maintain terminological databases for use in standardiza tion at the following addresses:  
— ISO Online browsing platform: available at http://www.iso.org/obp  
3.1  
baker’s yeast  
cells of one or more strains of the yeast  Saccharomyces cerevisiae  that aid the fermentation and aromatic 
activity of fermented doughs  
3.2  
Fresh Baker’s Yeast (FBY)  
baker’s yeast consist ing of living cells of Saccharomyces cerevisiae   
3.3  
Dry Baker’s Yeast (DBY ) 
baker’s yeast consist ing of living but  inactive cells of Saccharomyces cerevisiae  
3.2  
food grade material  
material, made of substances that  are safe and suitable for their intended use and which will not impart any 
toxic substance or undesirable odour or flavour to the product  
4 Types of baker’s yeast  
4.1 Baker’s yeast shall be categorised in two types:  
a) Fresh Baker’s Yeast;  and  
b) Dry Baker’s Yeast.  
4.2 Dry Baker’s Yeast  may  be in  the following forms;  
a) powder;  
b) small granules; and  
c) pellets or flakes . 
4.3 Fresh Baker’s Yeast  may be in three major forms:  
a) block or compre ssed yeast;  
b) granulated yeas t; or 
c) liquid yeast . 
5 Requirements   
5.1 General requirements  
Baker’s yeast  shall: 
a) be ivory in colour ;  
© EAC 2019  – All rights reserved  3 
 b) have an odour typical of yeast ; 
c) be free of extraneous materials ; 
d) not be slimy or mouldy ; and  
e) not show any sign s of deterioration or  decomposition . 
5.2 Specific requirements  
Baker’s yeast shall comply with the physicochemical characteristics given in Table 1 when tested in 
accordance with the methods specified therein . 
Table 1 — Physicochemical requirements for baker’s yeast  
 
S/N  
Characteristic Requirement  
Test method  
FBY DBY  
i)  Moisture, % (m/m) , max. 73 8 Annex A  
ii)  Edible starch, %  (m/m) , max. 7 10 ISO 15914  
iii)  Dispersibility in water  No yeast cell deposits  No yeast cell deposits   Annex B 
iv)  Fermenting power  (ml), min. 1 000 350 Annex  C 
v)  Dough -raising ca pacity  To satisfy the test  To satisfy the test  Annex  D 
5.2.1 Fresh Baker’s Yeast (FBY)  
5.2.1 .1 Block or compressed baker’s yeast  
This shall be in the form of a bloc k. The texture or consistency shall be either high plasticity (kneadable, 
deformati on possi ble without breakage) or friable/crumbly (blocks easily broken  into small pieces) . Permissible 
edible bin ders and fillers may be added in accordance to Codex Stan 192 . 
5.2.1.2  Granulated (crumbled) baker’s yeast  
This shall be in the form of small granules.  
5.2.1.3  Liquid baker’s yeast  
This s hall be  a liquid suspension of yeast cells in water  with a cream -like viscosity.  
5.2.2. 2 Dry baker’s yeast may be in two forms : 
a) active dry yeast -yeast that requires reactivation by rehydration using warm water between 38  °C – 45 
°C prior to use. It shall be of spheroid particles, 0.2 mm – 3 mm in diameter; and  
b) instant dry yeast -yeast dried in a way that rehydration is not necessary to facilitate reactivation. It shall 
consist of porous cylindrical yeast particles with an approximate diameter of 0.5 mm and length up to 
a few millimetres.  
6 Hygiene  
Bakers yeast shall be manufactured and han dled in accordance with EAS 39.   
4 © EAC  2019  – All rights reserved  
 6.1 Microb iological  requirements  
Baker’s yeast shall comply with the microbial limits given in Table 2 when tested in accordance with the 
methods specified therein . 
Table 2 — Microbi ological  limits for baker’s yeast  
S/N Characteristic Limits  
Test method  
FBY DBY   
i) Coliform count , cfu/g, max. 50 100 ISO 4832  
ii) Escherichia c oli, MPN /g Absent  ISO 7251  
iii) Salmonell a in 25 g Absent  ISO 6579 -1/  
ISO 6579 -2 
iv) Staphylococcus aureus cfu/g, max. 10 ISO 6888 -1/ 
ISO 6888 -2/ 
ISO 6888 -3 
v) Rope spore count , cfu/ g, max. 10 100 Annex E  
7 Pack aging  
Baker’s yeast shall be securely packaged in containers made of food grade material s. The packages shall 
preserve the  safety and  quality of the product, prevent entry of light and preclude contamination from the 
external environment . 
8 Weights and measures  
The products shall comply with the Weights and Measures Regu lations  in the respective  Partner State s. 
9 Labelling  
In addition to the labelling requirements of CODEX STAN 107, the packages shall be  legibly and indelibly 
marked with the following information:  
a) name and type of the product . For example, “Baker’s Yeast,  Granulated”, “Instant Baker’s Yeast”, 
“Granulated Baker’s Yeast”;  
b) name and physical address  of the processor/packer/importer ; 
c) date of manufacture;  
d) expiry  date;  
e) net weight  of the product in metric  units ; 
f) list of ingredients in descending order by quantity when used;  and 
g) declaration 'Contains edible starch', when  edible starch is added . 
11 Sampling  
Representative samples for the products shall be drawn in accordance with CAC/GL 50.   
© EAC 2019  – All rights reserved  5 
 Annex  A 
(normative)  
 
Determination of moisture  
A.1 Apparatus  
A.1.1 Dish,  with a cover, made of glass or aluminium, about 25 mm in diameter  
A.1.2 Glass stirring , approximately 60 mm long, with a flattened end  
A.2  Reagent  
Ethyl alcohol or rectified spirit.  
A.3  Procedure  
Weigh the dish with the cover and stirring rod ( M). Transfer t o this, add about 10 g of dry yeast or 2.5 g of 
fresh yeast and weigh accurately to the nearest milligram ( M1). 
Remove the cover of the dish and add 5 ml of alcohol. Mix thoroughly using the stirring rod and leave the 
stirring rod in the weighing dish. Pla ce the cover on the dish and dry at 105 °C ± 1 °C for 4 h for fresh baker’s 
yeast and 6 h for dry baker’s yeast. Cool the dish in a desiccator and weigh ( M2). 
A.4 Calculation  
The moisture content, expressed as percent by mass, shall be calculated as follow s: 
M MM M
 -)-(×100
12 1
 
where  
M is the mass, in grams, of the dish, its cover and the stirring rod;  
M1 is the mass, in grams, of the dish, its cover and the stirring rod with the sample before drying, and,  
M2 is the mass, in grams, of the dish, its cover and the stirring rod  with the sample after drying.  
 
  
6 © EAC  2019  – All rights reserved  
 Annex  B 
(normative)  
 
Test for dispersibility  in water  
B.1 Apparatus  
B.1.1  Beaker 400mL  
B.1.2  Measuring cylinder 100mL and 1000mL  
B.1.3  Thermometer  
B.2 Reag ent/material  
Distilled water  
B. 3 Procedure  
B. 3.1  Dry baker’s yeas t 
Weigh 5 g of dry baker’s yeast into a 400 -ml beaker and add 50 ml of distilled water at 40 °C. Leave the 
product undisturbed for 5 min and thereafter, stir for 2 min. To a one -litre graduated cylinder, add 900 ml of 
distilled water at 40 °C. Pour the slu rry in the beaker into the water in the graduated cylinder. Wash the beaker 
with 50 ml of distilled water, pour it into the cylinder and leave it undisturbed for 5 min. Check for any deposits 
at the bottom of the cylinder. If no deposits appear at the bott om of the cylinder, the material shall be 
considered to have passed the test.  
B.3.2 Fresh baker’s yeast  
Weigh 20 g of fresh baker’s yeast into a 400 ml beaker and add 50 ml of distilled water at 40 °C. Leave the 
product undisturbed for 5 min and thereafter , stir for 2 min. To a one -litre graduated cylinder, add 900 ml of 
distilled water at 30 °C. Pour the slurry in the beaker into the water in the graduated cylinder. Wash the beaker 
with 50 ml of distilled water, pour it into the cylinder and leave it undis turbed for 5 min. Check for any deposits 
at the bottom of the cylinder. If no deposits appear at the bottom of the cylinder, the material shall be 
considered to have passed the test.  
NOTE  If starch was added to the yeast, it may form a sediment which may c ontain a few yeast cells.   
© EAC 2019  – All rights reserved  7 
 Annex  C  
(normative)  
 
Determination of fermenting power  
C.1  Apparatus  
C.1.1  Fermentometer . The assembly of the apparatus is illustrated in Fig ure 1. It consists of a 250 ml flat-
bottomed flask (A) , whose mouth is fitted with a g round -glass joint having a glass delivery tube bent at right 
angle. It is connected to a  three -way T -shaped stop -cock (B) which in turn is fitted on a 100  ml graduated tube 
(D) of the manometer. E is the manometer reservoir o f 250  ml capacity. I is the iro n stand. D and E are 
connected by a PVC tube F. G is a waterbath.  
C.1.2  Barometer  
C.1.3  Thermometer  
C.2  Reagents  
C.2.1  Sugar phosphate mixture.  Grind and mix thoroughly 400 g of sucrose, 25 g of diammonium 
hydrogen phosphate [(NH 4)2 HPO 4] and 25 g of dipo tassium hydrogen phosphate (K 2HPO 4). 
C.2.2  Calcium sulphate solution.  Dilute 30 g of saturated calcium sulphate solution (CaSO 4 .2H 2O) with 
70 g of distilled water.  
C.2.3  Manometer solution.  Weigh 200 g of anhydrous calcium chloride and 10 g of cupric chlo ride and 
dissolve in distilled water. Add a little hydrochloric acid so that the final pH after making up the solution to two 
litres does not exceed 5.0.  
C.3  Procedure  
Mix 6.75 g of the sugar phosphate mixture with 75 ml of the caIcium sulphate solution i n the flask. Add to it, 
3.67 g of fresh baker’s yeast or 0.893 g of dry baker’s yeast. Stir well to disperse the yeast. Keep the flask in 
the waterbath at 30 °C throughout the experiment. Bring the three -way T -shaped stop -cock of the manometer 
into a posit ion which allows displacement of initial air (by the carbon dioxide evolved) to escape to the 
atmosphere without displacement of the manometer fluid. This displacement is allowed for the first 13 min 
after which the stop -cock position is altered to allow t he carbon dioxide evolved to enter the manometer and 
bring about the displacement of the manometer fluid. Shake the contents of the flask every 10 min.  
While taking the reading of the gas evolved, the level of the fluid in the manometer shall be adjusted b y sliding 
the reservoir arm of the manometer and the volume of gas evolved at this pressure (which will now be equal 
to the atmospheric pressure) shall be recorded.  
As soon as the reading is taken, the initial gas formed which has just been measured, is al lowed to escape 
into the atmosphere by operating the three -way stop -cock and the stop -cock position is again adjusted to take 
the second reading. For fresh baker’s yeast, readings should be taken every 10 minutes and for dry baker’s 
yeast, readings shall b e taken every 30 min. In both the cases, readings shall be taken for 3 h.  
The room temperature and the atmospheric pressure shall also be noted during the course of the experiment. 
The readings are recorded in a tabulated form (see Table C.1) and the total  volume of gas produced is 
calculated and corrected at 101 kPa pressure and 20 °C temperature by the formula given under C.4.  
 
  
8 © EAC  2019  – All rights reserved  
 
 
Figure 1 — Assembly of a fermentometor  
Table C.1 — Recording carbon dioxide evolved every 10/30 min  
 
Time  Volume of CO 2 
evolv ed 
ml Room temperature  
°C Atmospheric 
pressure  
mmHg  Corrected volume  
ml 
08:00  ……..  ……..  ……..  ……..  
08:10  ……..  ……..  ……..  ……..  
08:20  ……..  ……..  ……..  ……..  
08:30  ……..  ……..  ……..  ……..  
……..  ……..  ……..  ……..  ……..  
……..  ……..  ……..  ……..  ……..  
……..  ……..  ……..  ……..  ……. . 
……..  ……..  ……..  ……..  ……..  
11:00  ……..  ……..  ……..  ……..  
 
C.4  Calculation  
The fermenting power, expressed as corrected volume in millilitres, shall be expressed as follows:   
© EAC 2019  – All rights reserved  9 
 Corrected volume = 
e) temperatur room Average (273 x  760293  x pressure average Observedx  volume Observed
  
The mass of carbon dioxide  evolved, expre ssed in grams, may be calculated from this corrected volume as 
follows:  
Mass of carbon dioxide evolved = 
22400×44V   
where  
V is the corrected volume of carbon dioxide evolved.  
  
10 © EAC  2019  – All rights reserved  
 Annex  D  
(normative)  
 
Determination of dough raising capacity  
D.1 Apparatus  
D.1.1  Beaker 500 mL  
D.1.2  Measuring cylinder 100  mL 
D.2 Reagents  
D.2.1 Wheat flour  conforming to EAS 1  
D.2.2 Sucrose  
D.2  Procedure  
Mix 4.0 g of fresh baker's yeast or 1.0 g of dry baker's yeast with 100 g of wheat flour. Add 1.0 to 1.5 g of 
sucrose and a suitable quantity of water (about 55 ml). Knead well. Press the resulting dough into a glass 
beaker. Note the level of the dough by means of a scale, from the bottom of the beaker. Keep it covered for 
one hour at 27 °C. At the end of this period , note the level again.  
The product shall be deemed to have satisfied the test if the rise in level is at least 80 percent of the original 
for dry baker’s yeast and 110 % for fresh baker’s yeast.  
  
© EAC 2019  – All rights reserved  11 
 Annex  E 
(normative)  
 
Determination of bacterial rope spore  count  
E.1 Apparatus  
Flask 100 mL  
Conical flask 250 mL  
Water bath  
Pipppete 1 mL and 10 mL  
Petri dishes  
E.2 Reagents  
E.2.1 Sterilised peptone water , 0·1 % 
E.2.2 Tryptone glucose extract (TGE) Agar  composed of:  
 Tryptone 5.0 g;  
 Agar, bacteriological grade , 15.0 g. Granulated or chopped shreds, practically free from thermophilic 
bacteria shall be used ; 
 Yeast extract 2.5 g;  
 Distilled water, one litre;  
 Sodium chloride 6.5 g;  
 Glucose (dextrose) 1.0 g; and  
 Final pH of 7.0 ± 0.1. 
E.2  Procedure  
Weigh 22 g of wheat fl our in a suitable sanitised container and transfer to a conical flask containing 100 ml of 
sterile 0.1 %  pepton e water and sterile sand or glass beads. Blend on a shaker for about two minutes. Dilute 
the blended mixture further; 1:10, 1:100, 1:1 000, 1:10 000, etc., by dilution technique, using sterile peptone 
water.  
Prepare tryptone glucose extract (TGE) agar; 100 ml per 250 ml conical flask. Prepare one additional flask of 
medium to serve as sterility control. Sterilise at 121 °C for 15 min and then cool to 45 °C in a waterbath. 
Pipette volumes of the blended mixture into a series of TGE agar flasks while they are held in the waterbath; 
10 ml into the first, 1 ml into the second and 1 ml of each dilution into the third, fourth and fifth TGE flask and 
so on . Gently agitate the flasks to disperse the blended mixture throughout the medium.  
Transfer the flasks without delay to a waterbath adjusted to 65 °C to 90 °C and hold for 30 min with gentle 
shaking occasionally to assist heat distribution. After 30 min of  heat treatment, cool the flasks to about 45 °C  
12 © EAC  2019  – All rights reserved  
 without allowing the agar to gelatinise. Pour 100 ml of the medium into each flask representing the product 
and sterility control into a set of five sterile petri dishes in approximately equal volumes of abou t 20 ml per 
plate. When agar has solidified, invert the plates and incubate at 35 °C for 48 h.  
Count the surface and sub -surface colonies. The sum of the colonies on the set of five plates poured from 
TGE agar, containing 10 ml of the blended mixture repre sents the number of aerobic and mesophilic spores 
per gram of the product. Similarly, 1 ml of the blended and 1 ml of each dilution are equal to 0.01, 0.001, 
0.000 1 and 0.000 01 of the number of spores per gram and shall be multiplied by the respective di lution 
factor.  
Generally, the set of plates showing about 30 to 60 colonies per plate are to be chosen for the counting 
purposes.  
E.3  Precautions and limitations  
The procedure permits enumeration of aerobic and mesophilic spores in food samples containin g relatively 
higher number of spores by higher dilution of the samples prior to heat treatment.  
Certain thermophilic strains may also be indicated in this method in which case a separate enumeration 
method for thermophiles may be adopted and their numbers subtracted from the spore count.  
  
© EAC 2019  – All rights reserved  13 
 Bibliography  
[1] COFALEC (2012): General chara cteristics of dry baker’s yeast  
[2] COFALEC (2012): General charact eristics of fresh baker’s yeast  
[3] IS 1320 (1988) (Reaffirmed in 2010) — Specification for baker's yeast (Th ird Edition)  
 DEAS 997: 2019    
 
© EAC 2019  – All rights reserved