RWANDA STANDARD DRS 49 Second edition 2017-mm-dd Yoghurt Specification Reference number DRS 49:2017 RSB 2017
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 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without prior written permission from RSB. Requests for permission to reproduce this document should be addressed to: Rwanda Standards Board P.O Box 7099 Kigali-Rwanda KK 15 Rd, 49 Tel. +250 252 586103/582945 Toll Free: 3250 E-mail: info@rsb.gov.rw Website: www.rsb.gov.rw RSB 2017- All rights reserved ii
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 iii RSB 2017- All rights reserved
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) RSB 2017- All rights reserved iv
Rwanda Standards Board(RSB) Secretariat v 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) 1 RSB 2017- All rights reserved
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 RSB 2017- All rights reserved 2
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 microorganisms 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 shelflife. 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; 3 RSB 2017- All rights reserved
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 RSB 2017- All rights reserved 4
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. S/N Characteristic Whole milk Yoghurt Table 1 compositional requirements for plain 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 iii. Titratable acidity % lactic acid iv. Lactobacillus Bulgaricus and Streptococcus Thermophillus per g, min 4.3.2 Sweetened and flavoured Yoghurt 8.5 8.5 8.5 8.5 RS ISO 3728 0.6 1.2 0.6 1.2 0.6 1.2 0.6 1.2 ISO/TS 11869 10 7 10 7 10 7 10 7 Annex A/ ISO 9232 When tested in accordance with appropriate test methods, sweetened and/or flavoured yoghurt shall comply with the compositional requirements in table 2. 5 RSB 2017- All rights reserved
Table 2 Compositional requirements for sweetened yoghurt. S/N Characteristics Sweetened Yoghurt Partially skimmed sweetened yoghurt milk Skimmed sweetened yoghurt milk 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) III. Titratable acidity % lactic acid IV. 4.3.3 Fruit Yoghurt Lactobacillus bulgaricus and Streptococcus thermopiles per g (min) 8.5 8.5 8.5 RS ISO 3728 0.6 1.2 0.6 1.2 0.6 1.2 ISO/TS 11869 10 7 10 7 10 7 Annex A 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. RSB 2017- All rights reserved 6
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; 7 RSB 2017- All rights reserved
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. RSB 2017- All rights reserved 8
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. 9 RSB 2017- All rights reserved
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 A.5.2.4.5 Composition Agar 20 g Distilled water 1 000 ml. A.5.2.4.6 Preparation 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 RSB 2017- All rights reserved 10
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. A.6.1 Recommended culture media. 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. 11 RSB 2017- All rights reserved
A.6.2.5 Growth with 6.5 % NaCI. A.6.2.6 Culture medium. A.6.2.6.1 Composition M 17 broth (A.6.1.1.) without B-glycerol phosphate NaCI 6.6 %. A.6.2.6.2 Preparation 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. A.7.1 Recommended culture media. 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. RSB 2017- All rights reserved 12
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 Catalase - - - - Gas - - - - Production glucose from Growing temperature At 15 C-45 C Fermented Sugars No growth No growth No growth No growth + + + + Fructose + + ± + Galactose ± + + + Glucose + + + + Lactose - + + + Maltose + + + + Mannose - + ± + Sucrose - + - + Trehalose - + ± + Gluconate - - - - Cellobiose - - - + Rods with round end, singly, in pairs or short chains. No met achromatic bodies 13 RSB 2017- All rights reserved
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 RSB 2017- All rights reserved 14
ICS 67.100.10 RSB 2017 - All rights reserved