AFDC 05(6091) P3  
 
 
                  
DRAFT TANZANIA STANDARD  
 
 
 
 
 
 
Baker’s Yeast - Specification  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
                                    TANZANIA BUREAU OF STANDARDS                                                                                                                       
AFDC 05( 6091)P3  
 
 Baker’s Yeast - Specification  
 
0.  Foreword  
Baker’s ye ast are strains of yeast, essential for regulating the fermentation and aromatic activity of fermented 
doughs. These yeasts play three major roles; (i) increasing the volume of dough by producing carbon dioxide 
via alcoholic fermentation of sugars present in the dough, (ii) bringing about change in the structure and 
texture of the dough because of the carbon dioxide bubbles, and (iii), adding flavor to baked product.  
 
 
In preparation of this draft Tanzania standard assistance was drawn from India standard ( IS 1320: 2010 ) 
Specification for sucralose.  
 
Development of this Tanzania standard was necessitated by the need to ensure the safety and quality of 
Baker’s Yeast being produced and or marketed in Tanzania as well as for import and export markets.  
 
In report ing the result of a test or analysis made in accordance with the Tanzania standard, if the final value 
observed or calculated is to be rounded off, it shall be done in accordance with TZS 4  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
                                                                                                                        
AFDC 05( 6091)P3  
 
  
1 Scope  
This Draft Tanzania Standard specifies the requirements and the methods of sampling and test for baker's 
yeast.  
2 Normative references  
The following referenced documents are referred to in the text in such a way that some or all of their content 
constitutes requirements of this docume nt. For dated references, only the edition cited applies. For undated 
references, the latest edition of the referenced document (including any amendments) applies.  
Codex Stan 192, General Standard for Food Additives  
TZS 116, Labelling of food additives when sold as such — General requirements  
Codex Stan 193, General standard for contaminants and toxins in food and feed  
CAC/GL 50, General guidelines on sampling  
TZS 439, Wheat flour – Specification  
TZS 538, Labelling of pre -packaged foods — General require ments  
ISO 4832, Microbiology of food and animal feeding stuffs — Horizontal method for the enumeration of 
coliforms — Colony -count technique  
ISO 6579, Microbiology of food and animal feeding stuffs — Horizontal method for the detection of Salmonella 
spp. 
ISO 6888, Microbiology of food and animal feeding stuffs — Horizontal method for the enumeration of 
coagulase -positive staphylococci (Staphylococcus aureus and other species)  
ISO 7251, Microbiology of food and animal feeding stuffs — Horizontal method for t he detection and 
enumeration of presumptive Escherichia coli — Most probable number technique  
The Weights and Measures (Sales and Labelling of goods) Rules, 2007  
3 Terms and definitions  
For the purposes of this document, the following terms and definitions  apply.  
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 dry baker’s yeast  
baker’s yeast that consist of living but inactive cells of Saccharomyces  cerevisiae  
3.3 fresh baker’s y east  
Baker’s yeast that consist of living cells of Saccharomyces cerevisiae . 
3.4 food grade material  
a material, made of substances that are safe and suitable for their intended use and which will not impart any 
toxic substa nce or undesirable odor or flavor to the product.  
 
                                                                                                                        
AFDC 05( 6091)P3  
 
  
 
4. Types of baker’s yeast  
 
Baker’s yeast shall can be categorized in two types:  
 
4.1 Fresh baker’s yeast  
Fresh Baker’s Yeast  shall be in three major forms;  
(a) block or compressed this shall be in the form of a block.  
(b) granulated this shall be  in the form of small granules and  
(c) liquid this shall be a liquid suspension of yeast cells in water with a cream -like consistency .  
 
4.2 Dry baker’s yeast  
Dry Baker ’s Yeast shall be in two forms either acti ve or instant.  
(a) active dry yeast requires reactivation by rehydration using warm water between 38 °C – 45 °C prior to use.  
(b) instant dry yeast does not require rehydration to facilitate reactivation.  
 
5  Requirements   
5.1 General Requirements  
5.1.1 Fresh Baker’s Yeast (FBY)  
(a) Baker’s yeast shall be manufactured, packaged and stored under hygienic conditions in certified premises. 
Its distribution shall be under hygienic conditions. Bacteriologically free air filters shall be used for filtering the  
air required to aerate the fermenters.  
 
(b) Fresh Baker’s Yeast shall consist of living cells of Saccharomyces cerevisiae. Fresh Baker’s Yeast It shall 
be ivory in colour, with an odour typical of yeast and free of extraneous materials. It shall not be s limy or 
mouldy and shall not show any signs of deterioration or decomposition.  
 
(c ) Fresh baker’s yeast shall be in three major forms; block or compressed yeast, granulated yeast or liquid 
yeast.  
(i)  Block or compressed baker’s yeast  
This shall be in the fo rm of a block. The texture or consistency shall be either high plasticity (kneadable, 
deformation possible without breakage) or friable/crumbly (blocks easily broken into small pieces). Edible 
starch may be added in a quantity not exceeding 7 % (m/m) on dr y basis. Permissible edible binders and 
fillers may be added in accordance to Codex Stan 192.  
 
(ii) Granulated baker’s yeast  
This shall be in the form of small granules conform to the general requirement of fresh baker’s yeast as 
described in 5.1.1  
 
(iii)  Liquid baker’s yeast  
This shall be a liquid suspension of yeast cells in water with a cream -like viscosity and conform to the general 
requirement of fresh baker’s yeast as described in 5.1.1  
 
5.1.2  Dry Baker’s Yeast (DBY)  
 
(a) Dry baker’s yeast shall consist  of living but inactive cells of Saccharomyces cerevisiae. It shall be in 
the form of powder, small granules, pellets or flakes, dried to a low moisture content that stops the 
yeasts’ metabolic activity. It shall be ivory in colour, with an odour character istic of yeast and free from 
adulterants and other extraneous materials. It shall not be mouldy and shall not show any sign of 
deterioration or decomposition. Edible starch may be added in a quantity not exceeding 10 % (m/m) of 
the product.  
 
 
 
                                                                                                                        
AFDC 05( 6091)P3  
 
  
 
 
 
(b) Dry bak er’s yeast shall be in two forms; either active dry yeast or instant dry yeast.  
(i) Active dry yeast  
 
This is 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.  
 
(ii) Instant dry yeast  
This is yeast dried in a way that rehydration is not necessary to facilitate reactivation. I t shall consist of porous 
cylindrical  yeast particles with an approximate  average diameter of 0.5 mm and length up to a few 
millimeters  . 
 
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  
1 Moisture,  % (m/m), max.  73 8 Annex A  
2 Dispersibility in water  No yeast cell 
deposits  No yeast cell 
deposits  Annex B  
3 Fermenting power (ml), min  1000  350 Annex C  
4 Dough -raising capacity  To satisfy the test  To satisfy the test  Annex D  
 
 
6.0 Hygiene  
Baker’s yeast shall be manufactured and handled in accordance to EAS 39 and  
 
6.1 Microbial 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 — Microbial requirements for baker’s yeast  
S/N Characteristic  Requirement  Test method  
  FBY DBY  
 Coliform count, cfu/g,max  1000  50 ISO 4832  
 Escherichia coli,  MPN  cfu/g,  max Absent  
 ISO 16649  
 Salmonella cfu/per 25 g  Absent  ISO 6579 -1,  ISO 
6579 -2 
 Staphylococcus aureus cfu/g, 
max.  Absent  ISO 6888 -1, ISO 
6888 -2, ISO 6888 -3 
 Rope spore count, cfu /g, max  10 100 Annex E  
 
6 Contaminants  
The products shall comply with the contaminant limits cited in Codexstan 193.  
7 Sampling  
Representative samples for the products shall be drawn in accordance with  CAC/GL 50.  
 
                                                                                                                        
AFDC 05( 6091)P3  
 
 8 Packaging  
8.1 Fresh Baker’s Yeast  
Compressed and granulated baker’s yeast shall be packaged in clean waxed paper or any other suitable food 
grade wrapping material or non -toxic wrappers to preserve its freshness and to prevent undue deterioration 
during storage and distribution. Liquid bak er’s yeast shall be packed in containers suitable for liquid food 
stuffs.  
 
8.2 Dry Baker’s Yeast  
Dry baker’s yeast shall be packaged in clean, sound, air -tight food grade containers, preferably tin containers 
in such a manner as to prevent the absorption o f moisture and to prevent undue deterioration during storage 
and distribution.  
9 Marking and Labelling  
In addition to the labelling requirements of TZS 538, 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 manufacturer/distributor,  
 
c) Date of manufacture  
 
d) Best before date  
 
e) Net weight of the product in metric units,  
 
f) The list of additives in descending order by quantity when used,  
 
g) Declaration 'Contains edible starch', when edible starch is added  
 
h) Instructions for storage, and,  
 
i) Instructions of use  
 
9.2.2 The language on the label shall be “Kiswahili” or Kiswahili and English. A second language may be used 
depending on the designated market.  
9.2.3        The packages of the buns may also be marked with the TBS certification mark.  
NOTE - The TBS Standards M ark of Quality may be used by the manufacturers only under license from TBS. 
Particulars of conditions under which the licences are granted, may be obtained from TBS   
 
 
 
 
 
                                                                                                                        
AFDC 05( 6091)P3  
 
  
 
Annex A  
(normative)  
 
Determination of moisture  
 
A1 Apparatus  
- Dish - With a cover, made of glass or aluminium; about 25 mm in diameter  
 
- Glass stirring - Approximately 60 mm long, with a flattened end.  
 
- Dessicator  
 
- Oven  
A-2 Reagent  
- Ethyl alcohol or rectified spirit with a purity of 99.9%.  
 
A-3 Procedure  
Weigh the dish with the cover and stirring rod. Transfer to this, about 10 g of dry yeast or 2.5 g of fresh yeast 
and weigh accurately to the nearest milligram.  
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. Dry at 105 ± 1 °C for 4 hours for fresh baker’s yeast and 6 hours for dry 
baker’s yeast. Cool the dish in a desiccator and weigh  
 
A-4 Calculation  
 
The moisture, percent by mass = 100 × ( M1 - M 2 ) 
M1 - M 
 
where,  
M = mass, in grams of the dish, its cover and the stirring rod;  
 
M1 = mass, in grams of the dish, its cover and the stirring rod with the sample before drying, and,  
 
M2 = mass, in grams of the dish, its cover and the stirring rod with the sample after drying.  
 
 
                                                                                                                        
AFDC 05( 6091)P3  
 
  
 
 
Annex B  
(normative)  
 
Test for dispersibility in water  
B-1  
B-1 Apparatus  
Beaker 500mls and 50mls  
Cylinder 100mls and 1000mls  
Water bath, Thermometer  
B-2 Reagent  
Distilled water  
B-1 Procedure  
Weigh 5 g of dry baker’s yeast or 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 minutes and thereafter, stir for 2 minutes. Take into a one 
litre graduated cylinder, 900 ml o f distilled water at 40 °C in the case of dry baker’s yeast and at 30 °C for 
fresh baker’s yeast. Pour the slurry from 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 i t undisturbed for 5 minutes. 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 sedimen t which may contain a few yeast cells.  
 
 
 
 
 
 
 
 
 
                                                                                                                        
AFDC 05( 6091)P3  
 
  
Annex C  
(normative)  
Determination of fermenting power  
C-1.Apparatus  
 
- Fermentometer   
The assembly of the apparatus is illustrated in Fig. 1. It consists of a 250 ml flat -bottomed flask (A), whose 
mouth is fitted with a ground -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 of 250 ml capacity. I is the iron stand. D and E are connected by a PVC tube F. G 
is a water bath.  
 
- Barometer  
 
- Thermometer  
 
C-2 Reagents  
 
- Sugar phosphate mixture – Grind and mix thoroughly 400 g of sucrose, 25 g of diammonium  
hydrogen phosphate [(NH4)2 HPO4] and 25 g of dipotassium hydrogen phosphate (K2HPO4).  
 
- Calcium sulphate solution – Dilute 30 g of saturated calcium sulphate solution (CaSO4 .2H20) with 70 
g of distilled water.  
 
- Manometer solution – Weigh 200 g of anhydrou s calcium chloride and 10 g of cupric chloride and 
dissolve in distilled water. Add a little hydrochloric acid so that the final pH after making up the solution 
to 2 litres does not exceed 5·0.  
 
 
 
 
 
 
 
 
 
 
 
 
                                                                                                                        
AFDC 05( 6091)P3  
 
  
C-3 Procedure  
Mix 6.75 g of the sugar phosphate mixture with 75 ml of the caIcium sulphate solution in 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 water -bath at 30 °C through out the experiment. Bring the three -way T -shaped stop -cock of the manometer 
into a position 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 minutes 
after which the stop -cock position is altered to allow the carbon dioxide evolved to enter the manometer and 
bring about the displacement of the manometer fluid. Shake the contents of the flask every 10 minutes.  
 
While t aking the reading of the gas evolved, the level of the fluid in the manometer shall be adjusted by 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 reco rded.  
 
As soon as the reading is taken, the initial gas formed which has just been measured, is allowed 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 ba ker’s yeast, readings should be taken every 10 minutes and for dry baker’s 
yeast, readings shall be taken every 30 minutes. In both the cases, readings shall be taken for 3 hours,  
 
The room temperature and the atmospheric pressure shall also be noted durin g the course of the experiment. 
The readings are recorded in a tabulated form (see Table 2) 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. 
 
 
 
 
 
 
 7                                                                                                                        
AFDC 05( 6091)P3  
 
  
Table 2 Recording Carbon dioxide evolved every 10/30 minutes  
 
 Volume of CO2  Room  Atmospheric  
Corrected volume  
Time  evolved  temperature  pressure   
 
(ml) (°C) (mmHg)  (ml) 
  
08:00  ……..  ……..  ……..  ……..  
     
08:10  ……..  ……..  ……..  ……..  
     
08:20  ……..  ……..  ……..  ……..  
     
08:30  ……..  ……..  ……..  ……..  
     
……..  ……..  ……..  ……..  ……..  
     
……..  ……..  ……..  ……..  ……..  
     
……..  ……..  ……..  ……..  ……..  
     
……..  ……..  ……..  ……..  ……..  
     
11:00  ……..  ……..  ……..  ……..  
     
 
 
 
 
 
 
 
8                                                                                                                         
AFDC 05( 6091)P3  
 
 
 
C-4. Calculations  
 
 
Fermenting power (corrected volume in ml) 
=  
Observed volume x Observed average pressure x 
293 760 x (273 + Average room tem perature ) 
 
 
The mass of carbon dioxide evolved may be calculated from this corrected volume as  
 
 
Mass of carbon dioxide evolved =   
44 ×V 
22400   
g, where V is the corrected volume of carbon dioxide evolved.                                                                                                                         
AFDC 05( 6091)P3  
 
 Annex D  
(normative)  
Determination of dough raising capacity  
 
D-1. Materials  
 
- Wheat flour conforming to TZS 439  
 
- Sucrose  
 
- D.2 Apparatus  
 
- Beaker 500mls capacity  
 
- Measuring Cylinder 100mls  
 
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 percent for fresh bake r’s yeast.  
 
 
 
 
 
 
 
 
 
 
 
 
 
                                                                                                                        
AFDC 05( 6091)P3  
 
  
 
 
Annex E  
(normative)  
 
Determination of bacterial rope spore count  
F-1 Reagents  
 
-  
Sterilised peptone water - 0·1 percent.  
 
-  
Tryptone glucose extract (TGE) Agar  
 
 Tryptone 5.0 g   
● Agar, bacteriological grade (see Note) 15.0 g  
 
 Yeast extract 2.5 g   
● Distilled water 1 litre  
 
 Sodium chloride 6.5 g   
● Glucose (dextrose) 1.0 g  
 
 Final pH = 7.0 ± 0.1 
 
Note – Granulated or chopped shreds, practically free from thermophilic bacteria shall be used.  
 
F-2 Procedure  
Weigh 22 g of wheat flour in a suitable sanitised container and transfer to a conical flask containing 100 ml of 
sterile 0.1% peptone water and sterile sand or glass beads. Blend on a shaker for about two minutes. Dilute 
the blended mixture further; 1:10, 1:100, 1:1000, 1:10000, 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 1 5 minutes and then cool to 45 °C in a water -bath. 
Pipette volumes of the blended mixture into a series of TGE agar flasks while they are held in the water -bath; 
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 water -bath adjusted to 65 °C to 90 °C and hold for 30 minutes with 
gentle shaking occasionally to assist hea t distribution. After 30 minutes of heat treatment, cool the flasks to 
about 45 °C 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 5 sterile petri dishes in app roximately equal volumes of about 20 
ml per plate. When agar has solidified, invert the plates and incubate at 35 °C for 48 hours.  
Count the surface and sub -surface colonies. The sum of the colonies on the set of 5 plates poured from TGE 
agar, containing 1 0 ml of the blended mixture represents the number of aerobic and mesophilic spores per                                                                                                                        
AFDC 05( 6091)P3  
 
 gram of the product. Similarly, 1 ml of the blended and 1 ml of each dilution are equal to 0.01, 0.001, 0.0001 
and 0.00001 of the number of spores per gram and shall be multiplied by the respective dilution factor.  
 
Generally, the set of plates showing about 30 –60 colonies per plate are to be chosen for the counting 
purposes.  
 
F-3. Precautions and Limitations  
 
The procedure permits enumeration of aerobic and mesophilic sp ores in food samples containing 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 ma y be adopted and their numbers subtracted from the spore count.  
 
 
 
 
 
 
 
 
 
 
 
 
 
   AFDC 5 (6091 ) P1 
0 
 
DRAFT TANZANIAN STANDARD  
Bibliography  
 
[1] COFALEC (2012): General characteristics of dry baker’s yeast  
 
[2] COFALEC (2012): General characteristics of fresh baker’s yeast  
 
[3] IS 1320 (1988) (Third Edition) – Specification for baker's yeast (Reaffirmed in 2010)