rwanda standard - world trade organization · 2018. 1. 5. · iso 9232, yogurt -- identification of...

Reference number

DRS 49:2017

© RSB 2017

RWANDA STANDARD

DRS

49

Second edition

2017-mm-dd

Yoghurt — Specification

DRS 49:2017

©RSB 2017- All rights reserved ii

In order to match with technological development and to keep continuous progress in industries, standards are subject to periodic review. Users shall ascertain that they are in possession of the latest edition

© RSB 2017

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DRS 49:2017

iii ©RSB 2017- All rights reserved

Contents Page

1 Scope ...................................................................................................................................................... 1

2 Normative references ............................................................................................................................ 1

3 Terms and definitions ........................................................................................................................... 2

4 Requirements ......................................................................................................................................... 3 4.1 Ingredients ............................................................................................................................................. 3 4.1.1 Essential ingredients ............................................................................................................................ 3 4.1.2 Optional ingredients .............................................................................................................................. 4 4.2 General requirements ........................................................................................................................... 5 4.3 Composition of Yoghurt ....................................................................................................................... 5 4.3.1 Plain Yoghurt ......................................................................................................................................... 5 4.3.2 Sweetened and flavoured Yoghurt ...................................................................................................... 5 4.3.3 Fruit Yoghurt .......................................................................................................................................... 6 4.3.4 Heat treated yoghurt ............................................................................................................................. 6 4.4 Microbiological requirements .............................................................................................................. 6

5 Food additives ....................................................................................................................................... 6

6 Contaminants ......................................................................................................................................... 7 6.1 Heavy metals .......................................................................................................................................... 7 6.2 Pesticide and veterinary drug residues .............................................................................................. 7 6.3 Aflatoxins ............................................................................................................................................... 7

7 Hygiene ................................................................................................................................................... 7

8 Packaging ............................................................................................................................................... 7

9 Labelling ................................................................................................................................................. 7

10 Sampling ................................................................................................................................................ 8

Annex A (normative) Identification of Lactobacilus bulgaricus and Streptococcus thermophiles as characteristic microorganisms in yoghurt .................................................................................... 9

A.1 Scope ...................................................................................................................................................... 9 A.2 Definition ................................................................................................................................................ 9 A.3 Principle of the method......................................................................................................................... 9 A.4 Isolation of colonies .............................................................................................................................. 9 A.5 Phenotypic characteristics required for proper identification of l. bulgaricus; ............................. 9 A.5.1 Recommended culture media. ............................................................................................................. 9 A.5.2 Characteristics to consider ................................................................................................................ 10 A.6 Phenotypic characteristics required for a proper Identification of S.hermophilus. ..................... 11 A.6.1 Recommended culture media. ........................................................................................................... 11 A.6.2 Characteristics to consider: ............................................................................................................... 11 A.7 Expression of results .......................................................................................................................... 12 A.7.1 Recommended culture media. ........................................................................................................... 12 A.7.2 Characteristics to consider ................................................................................................................ 12 A.8 Expression of results .......................................................................................................................... 13

DRS 49:2017

©RSB 2017- All rights reserved iv

Foreword

Rwanda Standards are prepared by Technical Committees and approved by Rwanda Standards Board (RSB) Board of Directors in accordance with the procedures of RSB, in compliance with Annex 3 of the WTO/TBT agreement on the preparation, adoption and application of standards.

The main task of technical committees is to prepare national standards. Final Draft Rwanda Standards adopted by Technical committees are ratified by members of RSB Board of Directors for publication and gazettment as Rwanda Standards.

RS 49 was prepared by Technical Committee RSB/TC 004, Milk and milk products.

In the preparation of this standard, reference was made to the following standard (s):

1) KS 05-34, Yoghurt — Specification

2) SAZS 792, Yoghurt — Specification

The assistance derived from the above source is hereby acknowledged with thanks.

This second edition cancels and replaces the first edition (RS 49:2012), which has been technically revised.

Committee membership

The following organizations were represented on the Technical Committee on Milk and milk products (RSB/TC 004) in the preparation of this standard.

Enterprise Urwibutso

Global Trading Impex Serena Nice Cream (GTI)

Inyange Industries

Laiterie Nyabisindu

Ministry of Agriculture (MINAGRI/RALIS)

Agashinguracumu Ltd

Rwanda Consumer’s Rights Protection Organization (ADECOR)

Rwanda National Dairy Platform (RNDP)

DRS 49:2017

v ©RSB 2017- All rights reserved

Rwanda Standards Board(RSB) – Secretariat

DRS 49:2017

1 ©RSB 2017- All rights reserved

Yoghurt — Specification

1 Scope

This standard specifies requirements, sampling and test methods for yoghurt.

This standard shall apply to different types of yoghurt such as plain, sweetened, fruit, flavoured, and heat treated.

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 193, Codex general standard for contaminants and toxins in foods

ISO 14501, Milk and milk powder -- Determination of aflatoxin M1 content -- Clean-up by immunoaffinity chromatography and determination by high-performance liquid chromatography

ISO 8069, Dried milk -- Determination of content of lactic acid and lactates

ISO 9232, Yogurt -- Identification of characteristic microorganisms (Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus)

ISO/TS 11869, Fermented milks -- Determination of titratable acidity -- Potentiometric method

RS CAC/RCP 1, General Principle for Food Hygiene.

RS CODEX STAN 192, Codex general standard for food additives

RS CODEX STAN 212, Sugars –Specification

RS EAS 38, General standard for labelling of pre-packaged foods

RS ISO 10560, Milk and milk products – Detection of Listeria monocytogenes

RS ISO 11290-2, Microbiology of food and animal feeding stuffs — Horizontal method for the detection and enumeration of Listeria monocytogenes —Part 2: Enumeration method

RS ISO 11866-2, Milk and milk Products-Enumeration of presumptive Escherichia coli-part 2: colony-count technique at 44oC using membranes

RS ISO 2446, Milk — Determination of fat content (Routine method)

©RSB 2017- All rights reserved 2

RS ISO 3728, Ice-cream and milk ice -- Determination of total solids content (Reference method)

RS ISO 6579-1, Microbiology of the food chain -- Horizontal method for the detection, enumeration and serotyping of Salmonella -- Part 1: Detection of Salmonella spp.

RS ISO 6611, Milk and milk products- Methods of microbiological examination part 3: Enumeration of colony forming units of yeasts and/or moulds-colony-count technique at 25 degrees celcius

RS ISO 707, Milk and milk products — Guidance on sampling

3 Terms and definitions

For the purposes of this standard, the following terms and definitions apply.

3.1

yoghurt

coagulated milk product obtained by lactic acid fermentation through the action of Lactobacillus bulgaricus and Streptococcus thermophillus and other suitable bacteria from milk products which have been pasteurized prior to fermentation.

Note: Other suitable bacteria may be other Lactobacilli spp and Bifidobacteria are also sometimes added during or after

culturing yogurt.

3.2

plain Yoghurt

yoghurt as defined in clause 3.1 to which no sugar and food additives have been added

3.3

fruit Yoghurt

yoghurt as defined in clause 3.1 to which fruits have been added to characterize the flavour

3.4

flavoured Yoghurt

yoghurt as defined in clause 3.1 to which flavouring essences, foods or ingredients have been added with or without added sugars and/or colouring substances to characterize the flavour

3.5

sweetened Yoghurt

natural yoghurt as defined in clauses 3.1 to 3.4 which carbohydrate sugar has been added

DRS 49:2017


3.6

heat-Treated Yoghurt

yoghurt as defined in clauses 3.1. to 3.4 which has been subjected to heat treatment after fermentation. It may not contain viable and abundant micro-organisms

3.7

pasteurized yoghurt

yoghurt which has been subjected to a pasteurization process for the purpose of destroying most of the micro-organisms and extending the shelf life.

3.8

thermized yoghurt

yoghurt that has been heat-treated aimed at reducing the number of viable organisms and prolonging shelf-life.

4 Requirements

4.1 Ingredients

All ingredients used for the manufacture of yoghurt shall be of good quality and shall comply with the relevant standards.

4.1.1 Essential ingredients

All yoghurts shall be made from any of the following milk and milk products and essential additions. The basic mix ingredients shall be pasteurized before fermentation.

4.1.1.1 Milk and milk products

Those products include:

a) pasteurized milk;

b) evaporate or condensed milk;

c) pasteurized partly skimmed milk;

d) evaporated or condensed partly skimmed milk;

e) pasteurized skimmed milk;

f) evaporated or condensed skimmed milk;


g) pasteurized cream; and

h) a mixture of two or more products.

4.1.1.2 Yoghurt cultures

The following cultures shall be added to all types of yoghurt:

a) Cultures of Lactobacillus bulgaricus; and

b) Streptococcus thermophillus

4.1.2 Optional ingredients

The following ingredients may be added to all types of yoghurts. Those include but are not limited to:

4.1.2.1 Milk products which shall have been pasteurized in their production:

a) milk powder;

b) skimmed milk powder;

c) unfermented buttermilk;

d) concentrated whey;

e) whey proteins;

f) whey protein concentrates;

g) water soluble milk proteins;

h) edible casein; and

i) caseinates.

4.1.2.2 Other suitable lactic acid producing bacteria cultures in addition to those in 4.1.1.2

4.1.2.3 Sugars (in sweetened types of yoghurt only), complying with RS CODEX STAN 212.

4.1.2.4 Permitted flavours conforming to RS CODEX STAN 192

DRS 49:2017


4.2 General requirements

Yoghurt shall:

a) be free from off flavours and off odours such as metallic flavour or yeast flavour;

b) be free from foreign matter;

c) have the characteristic taste and flavour of the type of yoghurt;

d) be free from bitterness; and

e) be free from coarseness due to over ripening.

4.3 Composition of Yoghurt

All types of yoghurt when tested according to Annex A shall contain characteristic microorganisms of L.bulgaricus and S. thermophilus. Other compositional factors may vary depending on the milk fat content of the milk part of yoghurt.

4.3.1 Plain Yoghurt

When tested in accordance with appropriate test methods, plain yoghurt shall comply with the requirements specified in table 1.

Table 1 ▬ compositional requirements for plain yoghurt

S/N Characteristic

Whole milk

Yoghurt

Partially

skimmed milk

yoghurt

Skimmed milk

Yoghurt

High fat

yoghurt

Test method

i. Milk fat % m/m 3.0- 7 >0.5 -<3 0.5(min) 7 (min) RS ISO 2446

ii. Milk solids not fat %

m/m ,min 8.5 8.5 8.5 8.5 RS ISO 3728

iii. Titratable acidity %

lactic acid 0.6 – 1.2 0.6 – 1.2 0.6 – 1.2 0.6 – 1.2 ISO/TS 11869

iv. Lactobacillus Bulgaricus and

Streptococcus Thermophillus per g ,

min

107 107 107 107 Annex A/ ISO

9232

4.3.2 Sweetened and flavoured Yoghurt

When tested in accordance with appropriate test methods, sweetened and/or flavoured yoghurt shall comply with the compositional requirements in table 2.


Table 2 ▬ Compositional requirements for sweetened yoghurt.

S/N

Characteristics

Sweetened

Yoghurt

Partially skimmed milk

sweetened

yoghurt

Skimmed milk sweetened

yoghurt

Test method

I. Milk fat % 2.25 (min) >0.5 –1.25 (max) 0.5 (max) RS ISO 2446

II. Milk solids not fat %

m/m (min)

8.5 8.5 8.5 RS ISO 3728

III. Titratable acidity %

lactic acid 0.6 – 1.2 0.6 – 1.2 0.6 – 1.2 ISO/TS 11869

IV. Lactobacillus

bulgaricus and Streptococcus

thermopiles per g

(min)

107 107 107 Annex A

4.3.3 Fruit Yoghurt

The milk part of fruit yoghurt or yoghurt containing food materials shall comply with the requirements of sweetened yoghurt in table 2. The minimum amount of yoghurt in the final product shall be 70 % m/m.

4.3.4 Heat treated yoghurt

In addition to the compositional requirements in clause 4.3.1, 4.3.2 and 4.3.3. Heat treated yoghurt may have no live micro-organisms.

4.4 Microbiological requirements

Yoghurt shall comply with the microbiological requirements specified in Table 2.

Table 2 ▬ Microbiological requirements

S/N Microorganisms Maximum limits (CFU per ml) Test method

i. E.coli CFU/ml Absent RS ISO 11866-2

ii. Salmonella spp in 25ml Absent RS ISO 6579-1

iii. L monocytogenes, CFU/ml Absent RS ISO 10560

iv. Moulds, CFU/ml 10 RS ISO 6611

v. Yeasts, CFU/ml 10

5 Food additives

Food additives which may be used shall comply with RS CODEX STAN 192.

DRS 49:2017


6 Contaminants

6.1 Heavy metals

The products covered by this standard shall comply with the maximum limits established by the Codex Alimentarius Commission.

6.2 Pesticide and veterinary drug residues

The products covered by this standard shall comply with the maximum residue limits for veterinary drug and pesticide residues established in Codex Standard Guide for Maximum Pesticide Limits in Foods.

6.3 Aflatoxins

When tested in accordance with ISO 14501, the level of Aflatoxin M1shall not exceed 0.50μg/l

7 Hygiene

The product covered by the provisions of this standard shall be prepared and handled in accordance with RS CAC/RCP 1.

8 Packaging

Yoghurt shall be packaged in food grade containers which shall safeguard the quality of the product

9 Labelling

In addition to the requirements specified in RS EAS 38, the following requirements shall apply:

a) name of the product as plain yoghurt, fruit yoghurt, flavoured yoghurt or sweetened yoghurt.;

b) name, address and physical location of the manufacturer;

c) list of ingredients;

d) lot number;

e) date of manufacture;

f) expiry date;

g) Country of origin;


h) Net contents in volume;

i) Storage conditions;

j) Lot number;

k) Origin of milk used if different from cow’s milk;

l) Declaration of partly skimmed milk yoghurt as fat reduced yoghurt;

m) For heat-treated yoghurt, declaration as either pasteurized or thermised;

n) Declaration of milk fat content as a percentage by mass; and

o) Declaration or products with a liquid consistency as ‘’drinking yoghurt’’.

10 Sampling

Sampling shall be done in accordance with RS ISO 707.

DRS 49:2017


Annex A (normative)

Identification of Lactobacilus bulgaricus and Streptococcus thermophiles as characteristic microorganisms in yoghurt

A.1 Scope

A1.1 This method specifies the simplified methods using the cultural and physiological properties for identification of the characteristic micro-organisms.

A1.2Field of application: The method is applicable to the strains isolated from plain, flavoured, stirred or unstirred yoghurt and fruit yoghurts, where both characteristic micro-organisms are viable and abundant.

A.2 Definition

For the purpose of this standard the following definitions shall apply: Characteristic micro-organisms: Lactobacillus bulgaricus and Streptococcus thermophilus.

A.3 Principle of the method

a) Determination of morphological, cultural and biochemical characteristics for E. bulcaricus.

b) Determination of morphological, cultural and biochemical characteristics for S. Thermophilus.

A.4 Isolation of colonies

See A.6

A.5 Phenotypic characteristics required for proper identification of l. bulgaricus;

A.5.1 Recommended culture media.

A.5.1.1 For routine cultures and physiological tests: autoclaved skimmed milk and Mrs. Broth.

A.5.1.2 For special tests, for example fermentation tests, use a basic medium (BM), similar to that of MRS* without glucose and meat extract, at pH 6.9-7, which is supplied with the producer’s diagnostic kits.


A.5.2 Characteristics to consider

A.5.2.1 Morphology

Cultures on skimmed milk should be freshly made. Smears of cultures stained with methylene blue for few minutes. (Observe the presence of voluting grains after 24 hours incubation at 37°C in skimmed milk.)

A.5.2.2 Catalase Activity

Mix equal volumes of every broth culture with 1.5 % hydrogen peroxide in a test with a rubber. Invert the catalase tubes and observe for about 20 min at room temperature. Controls are prepared simultaneously. Under these conditions L. bulgaricus will not develop in oxygen.

A.5.2.3 Growth on MRS.

Broth at 15 °C and 45 °C - inoculate one drop on a 18 – 24 h culture and observe for up to 7 days. No turbidity at 15° C: turbidity at 45 °C.

A.5.2.4 Production of C02 from glucose:

A.5.2.4.1 Culture medium.

A.5.2.4.2 Composition

BM (A5.1.2) per cent glucose.

A.5.2.4.3 Preparation

Dissolve and distribute 10 ml of culture medium (A5.2.4.1) in tubes of 16 mm x 160 mm, and sterilize at 121 °C for 15 min.

A.5.2.4.4 White agar


Agar 20 g Distilled water 1 000 ml.


Dissolve and distribute 10 m l of white agar in tubes of 16 mm x 160 mm and sterilize at 121 °C for 15 min.

A.5.2.4.7 Procedure

Inoculate culture medium with 1 per cent of the culture grown on MRS. Cover the surface to a depth of 1 cm white agar (avoid any trace on the interior surface of the tube). Incubate at 37 °C for 15 days. Presence of gas

DRS 49:2017


is evident when the white agar layer detaches itself from the underlying contents. In these conditions L. bulgaricus does not produces gas.

A.5.2.5 Fermentation of Sugars

Table 1 indicates the important sugars to distinguish L. bulgaricus from the taxonomically nearest group of thermo-bacteria.

A.5.2.5.1 Culture medium

A.5.2.5.2 BM plus diagnostic kit (clause 5.1.2) for lactobacillus.

A.5.2.5.3 Procedure

For preparation of the inoculums and reading of results see directions of the commercial micro methods.

A.5.2.6 Determination of Lactic Acid Isomers in the Culture

See ISO 8069: International standard for lactic acid and lactates content.

A.6 Phenotypic characteristics required for a proper Identification of S.hermophilus.


For routine cultures and physiological tests autoclaved litmus milk and M 17 broth.

A.6.2 Characteristics to consider:

A.6.2.1 Morphology

Cultures on litmus ilk should be freshly made. Smears of cultures stained with methylene blue for a few minutes.

A.6.2.2 Catalase Activity

See A.5.2.2. Under these conditions S. thermophilus will not develop oxygen.

A.6.2.3 Growth on litmus milk at 10 °C and 45 °C

For procedure see A.5.2.3 At 10 °C.S. thermophiles does not change litmus milk.

A.6.2.4 Action on litmus milk (acidification, coagulation, and reduction)

Litmus milk acidified by S.thermophilus turns pink and then coagulates, after coagulation the color remains pink due to incomplete reduction of litmus, with a more intensely coloured upper ring.


A.6.2.5 Growth with 6.5 % NaCI.

A.6.2.6 Culture medium.


M 17 broth (A.6.1.1.) without B-glycerol phosphate NaCI 6.6 %.


Dissolve and distribute 10 ml aliquots of A6.2.6.1 in tubes of 16 mm x 160 mm and sterilize at 121°C for 15 min.

A.6.2.6.3 Procedure

Inoculate the tubes with a drop of washed cells suspension of overnight M 17 broth culture of the strains to be tested. Incubate at 37 °C and observe the growth for up to 7 days. In these conditions S. thermophilus does not develop.

A.7 Expression of results

Compare the results of the tests of Clause 7 with main attributes Expressed on Table 1, for bulgaricus and compare the results of the tests of Clause 8 with main attributes expressed in Table 2 for S. thermophilus.


For routine cultures and physiological tests autoclaved litmus milk and M 17 broth.

A.7.2 Characteristics to consider

A.7.2.1 Morphology – Cultures on litmus ilk should be freshly made. Smears of cultures stained with methylene blue for a few minutes.

A.7.2.2 Catalase Activity – See clause A5.2.2. Under these conditions S. thermophilus will not develop oxygen.

A.7.2.3 Growth on litmus milk at 10°C and 45°C – For procedure see clause A5.2.3 At 10°C.S. thermophilus does not change litmus milk.

A.7.2.4 Action on litmus milk (acidification, coagulation, and reduction) – Litmus milk acidified by S. thermophilus turns pink and then coagulates, after coagulation the color remains pink due to incomplete reduction of litmus, with a more intensely coloured upper ring.

A.7.2.5 Growth with 6.5 per cent NaCI.

DRS 49:2017


A.7.2.6 Culture medium.

A.7.2.6.1 Composition – M 17 broth (A6.1.1.) without B-glycerol phosphate NaCI 6.6 %.

A.7.2.6.2 Preparation – Dissolve and distribute 10 ml aliquots of A.7.2.6.1 in tubes of 16 mm x 160 mm and sterilize at 121°C for 15 min.

A.7.2.6.3 Procedure – Inoculate the tubes with a drop of washed cells suspension of overnight M 17 broth culture of the strains to be tested. Incubate at 37°C and observe the growth for up to 7 days. In these conditions S. thermophilus does not develop.

A.8 Expression of results

A.8.1 Compare the results of the tests of Clause 7 with main attributes Expressed on Table 1, for bulgaricus

A.8.2 Compare the results of the tests of Clause 8 with main attributes expressed in Table 2 for S. thermophiles

Table A.1 ▬ Main attributes of L. bulgaricus, L. lactis, L. Helveticas

Attributes L. bulgaricus L. lactis L. helveticsu L. acidophilus

Morphology Rods with round

variable according to age, medium, strain.

Numerous metachromatic bodies

of cells of old culture stained with

methylene blue

As L; bulgaricus Polymorphism of old

culture not so marked as with L. Bulgaricus.

No met achromatic

bodies

Rods with round end,

singly, in pairs or short chains. No met

achromatic bodies

Catalase - - - -

Gas - - - -

Production from

glucose

No growth No growth No growth No growth

Growing temperature

At 15°C-45°C

+ + + +

Fermented Sugars

Fructose + + ± +

Galactose ± + + +

Glucose + + + +

Lactose - + + +

Maltose + + + +

Mannose - + ± +

Sucrose - + - +

Trehalose - + ± +

Gluconate - - - -

Cellobiose - - - +


Esculine - - - +

Lactic acid isomer D(-) D(-) DL DL

NOTE 1 + = positive reaction for 90 % or more strains

NOTE 2 - = negative reaction for 90 % or more strains.

NOTE 3 ± = variable reaction, weak, slow or negative

rwanda standard - world trade organization · 2018. 1. 5. · iso 9232, yogurt -- identification of...

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