1、| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BRITISH STANDARD BS 4317-21:1999 ICS 67.06
2、0 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW Methods of test for Cereals and pulses Part 21: Determination of rheological properties of doughs using an extensographThis British Standard, having been prepared under the direction of the Consumer Products and Services Sector
3、 Committee, was published under the authority of the Standards Committee and comes into effect on 15 December 1999 BSI 12-1999 The following BSI references relate to the work on this standard: Committee reference AW/4 Draft for comment 95/502232 DC ISBN 0 580 33055 9 BS 4317-21:1999 Amendments issue
4、d since publication Amd. No. Date Comments Committees responsible for this British Standard The preparation of this British Standard was entrusted to Technical Committee AW/4, Cereals and pulses, upon which the following bodies were represented: Agricultural Engineers Association Association of Publ
5、ic Analysts Campden and Chorleywood Food Research Association Grain and Feed Trade Association Home Grown Cereals Authority Institute of Brewing Institute of Food Science and Technology Intervention Board Maltsters Association of Great Britain Ministry of Agriculture, Fisheries and Food NABIM Nation
6、al Farmers Union Natural Resources Institute United Kingdom Agricultural Supply Trade Association Ltd.BS 4317-21:1999 BSI 12-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Normative references 1 3 Definitions 1 4 Principle 1 5 Reagents 1 6 Apparatus 1 7 Proced
7、ure 1 8 Expression of results 2 Annex A (informative) Repeatability and reproducibility 3 Table A.1 Repeatability: limits of result differences 3 Table A.2 Reproducibility: limits of result differences 3 Table A.3 Resistance after 45 min 3 Table A.4 Results of interlaboratory tests for resistance af
8、ter 45 min 4 Table A.5 Extensibility after 45 min 4 Table A.6 Results of interlaboratory tests for extensibility after 45 min 4 Table A.7 Resistance after 90 min 5 Table A.8 Results of interlaboratory tests for resistance after 90 min 5 Table A.9 Extensibility after 90 min 5 Table A.10 Results of in
9、terlaboratory tests for extensibility after 90 min 6 Table A.11 Resistance after 135 min 6 Table A.12 Results of interlaboratory tests for resistance after 135 min 6 Table A.13 Extensibility after 135 min 7 Table A.14 Results of interlaboratory tests for extensibility after 135 min 7ii BSI 12-1999 B
10、S 4317-21:1999 Foreword This part of BS 4317 has been prepared by Technical Committee AW/4, Cereals and pulses. It supersedes BS 4317-21:1989, which is withdrawn. This British Standard is derived from ICC Standard Method No. 114/1, published by the International Association for Cereal Science and Te
11、chnology. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document
12、comprises a front cover, an inside front cover, pages i and ii, pages 1 to 7 and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued. BSI 12-1999 1 BS 4317-21:1999 1) This part of BS 4317 has been prepared based on work with the Brabender Ext
13、ensograph. This information is given for the convenience of users of this part of BS 4317 and does not constitute an endorsement by BSI of this product. 1 Scope This part of BS 4317 specifies a method, using an extensograph 1) , for determination of the stretching characteristics of a wheat flour do
14、ugh. The method is applicable to white and brown wheat flours. Details of an interlaboratory trial on the repeatability and reproducibility of results gained using the method specified in this British Standard are given in annex A. 2 Normative references The following normative documents contain pro
15、visions that, through reference in this text, constitute provisions of this part of this British Standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. For undated references, the latest edition of the publication referred to applies. BS 43
16、17-20, Determination of water absorption of flour and rheological properties of doughs using a farinograph. 3 Definitions For the purposes of this part of BS 4317, the following definition applies. 3.1 stretching characteristics (of dough) resistance to extension (expressed in Brabender extensograph
17、 units, BU) and extent to which it can be stretched until breaking (“extensibility”; expressed in millimetres transposition of the recorder paper) 4 Principle A floursaltwater dough is prepared under standard conditions in a farinograph and moulded on the extensograph into a standard shape. After a
18、fixed time the dough is stretched and a curve drawn recording its extensibility and resistance to stretching. The dough is immediately remoulded and, after a fixed time, restretched. The remoulding, resting and stretching are repeated once more. The size and shape of the curves obtained are a guide
19、to the baking characteristics of the flour. 5 Reagents 5.1 Distilled water or deionized water or water of equivalent purity. 5.2 Sodium chloride, analytical reagent grade. 5.3 Liquid paraffin. 6 Apparatus NOTE All measuring equipment should be calibrated. 6.1 Extensograph, with constant temperature
20、water circulating tank. 6.2 Farinograph, with 300 g bowl, burette and constant temperature water circulating tank (see BS 4317-20). 6.3 Balance, at least able to weigh 300 g with an accuracy of 0.1 g. 6.4 Plastics scraper. 6.5 Conical flask or beaker, 250 ml. 6.6 Funnel. 6.7 Scissors. 6.8 Thermomete
21、r, graduated in intervals of 0.18C. 6.9 Timer, at least able to read in intervals of 1 s. NOTE If the apparatus includes an integral timing device, this should not be used for the test. 6.10 Ruler. 7 Procedure 7.1 Operation of the extensograph Turn on the thermostat and circulate the water until it
22、reaches 308C 0.58C. Before use, check that the temperature of the extensograph cabinet is 308C 0.58C. Lightly grease the dough holders with liquid paraffin. Place some water in the troughs of the dough holder cradles and return these to the dough cabinets at least 15 min before use. Ensure that the
23、chart paper is correctly aligned on the sprockets of the chart recorder. When the extensograph balance arm is moved the pen should follow the arcs on the chart paper. The pen should be on the zero line when a dough holder with clamps and 150 g weight is placed in position on the extensograph balance
24、 arm. 7.2 Dough preparation Allow the flour to equilibrate to 25.08C 5.08Ci f required. Before carrying out the tests mix a scrap dough. NOTE For this purpose the salt and rest period may be omitted. Place 300.0 g 0.1 g of flour in the farinograph bowl. Close the lid to engage the safety switch. Fil
25、l the burette, including the tip, with water at 30.08C 2.08C. Place 6.0 g of sodium chloride into the conical flask (or beaker). Run in 135 ml of water from the burette and dissolve the sodium chloride.2 BSI 12-1999 BS 4317-21:1999 Set the pen on a 9 min line on the farinograph chart paper. Start mi
26、xing the dry flour with the motor running at approximately 63 r/min. Position the funnel in the central hole in the lid. As the pen crosses the 0 min line pour the sodium chloride solution through the funnel into the bowl. Tap the funnel to release any adhering drops into the bowl. Add further water
27、 from the burette, through the front end of the right hand slot in the lid, to a volume estimated to give a dough consistency of 500 BU at the end of the mixing procedure. When the dough forms, carefully use the plastics scraper to push any flour or dough adhering to the mixing bowl walls down into
28、the mixture. Mix for 1 min from the start of water addition. After 1 min from the start of water addition, switch off the farinograph motor and allow the dough to rest in the covered bowl for 5 min. After the rest period, mix for a further 2 min with the motor running at approximately 63 r/min. NOTE
29、 1 The final dough consistency should be 500 BU 20 BU. NOTE 2 During the second mixing period additional water may be added only to estimate the water addition for a further mixing of the same flour. Doughs produced under these conditions should not be stretched as the dough structure is not uniform
30、. 7.3 Dough shaping Remove the dough from the mixer with minimum handling, taking care that it is not pulled or deformed in the process. Use the scissors to scale off 150 g of the dough as near as possible in one piece. Place this in the balling unit and mould (20 revolutions of the plate). Remove f
31、rom the balling unit and pass once through the moulder ensuring that the dough piece enters the moulder centrally positioned and base first. Take a cradle and dough holders from the cabinet and remove the clamps. Roll the test piece from the moulder into the centre of a holder, clamp in position and
32、 replace the dough holder in the cradle. Set the timer to 45 min. Weigh a second dough piece and ball, mould and clamp as before. Place the cradle with dough holders and dough pieces in the cabinet and shut the door. 7.4 Dough stretching Ensure that the pen is on the extensograph chart paper. 45 min
33、 after clamping the first dough piece, place the first dough holder in position on the balance arm of the extensograph with the bridge between the two halves of the dough holder on the left hand side to avoid impeding the hook. Immediately start the hook descending. Once the dough piece has broken,
34、remove the dough holder from the balance arm, collect the dough from the dough holder and hook and repeat the balling and moulding operations in accrdance with 7.3. Reset the timer to 45 min. NOTE 1 With new models of extensograph the hook should stop automatically and return to the start position.
35、With older models the hook should be stopped by use of a switch after the dough piece breaks and to start it returning to its upper position. Measure extensibility to the point where the dough first breaks. NOTE 2 Generally one of the dough pieces should break before the other. If so, the point at w
36、hich the dough first breaks may be made clearer by gently nudging the extensograph balance arm upwards immediately the piece breaks. Turn the chart paper back to the same start position as for the first dough. Repeat the stretching procedure on the second dough piece. Collect the dough from the doug
37、h holder and hook. Repeat the balling and moulding operations in accordance with 7.3 on the second dough piece. Move the pen to a fresh position on the extensograph chart. 45 min after returning the first dough piece to the resting cabinet, repeat the stretching operation in accordance with 7.4 and
38、the balling and moulding operations in accordance with 7.3, returning the moulded test pieces to the cabinet. Move the pen to a fresh position on the extensograph chart. 45 min after returning the first dough piece to the resting cabinet, repeat the stretching operation in accordance with 7.4. When
39、the dough piece breaks, remove from the dough holder and hook and discard. Turn the chart paper back to the same start position as for the first dough piece. Repeat the stretching operation described in accordance with 7.4 on the second dough piece. When the dough piece breaks, remove from the dough
40、 holder and hook and discard. 8 Expression of results 8.1 Resistance Report the resistance (the mean maximum height of the curves from the two dough pieces) at each test time (45 min, 90 min and 135 min) to the nearest 5 BU. 8.2 Extensibility Report the extensibility (the mean distance travelled by
41、the chart paper from the moment the hook touches the dough piece until the dough piece first breaks) at each test time (45 min, 90 min and 135 min) to the nearest millimetre.BS 4317-21:1999 BSI 12-1999 3 Annex A (informative) Repeatability and reproducibility A.1 Repeatability r Values for the diffe
42、rence between two independent single test results obtained by the method specified in this British Standard, from examination of identical test material in the same laboratory by the same operator using the same equipment and within a short interval of time, are given in Table A.1. Table A.1 Repeata
43、bility: limits of result differences Test time Resistance Extensibility 45 min 45 BU 13 mm 90 min 70 BU 14 mm 135 min 65 BU 23 mm A.2 Reproducibility R Values for the difference between two single test results obtained by the method specified in this British Standard, from examination of identical t
44、est material in different laboratories with different operators using different equipment, are given in Table A.2. Table A.2 Reproducibility: limits of result differences Test time Resistance Extensibility 45 min 140 BU 23 mm 90 min 205 BU 29 mm 135 min 240 BU 30 mm A.3 After 45 min A.3.1 Resistance
45、 The results of interlaboratory trials to determine the resistance after 45 min are given in Table A.3. Table A.3 Resistance after 45 min Measurement Sample A Sample B Sample C Total Number of laboratories 7 7 7 7 Number of results 14 14 14 42 Number of laboratories retained after deletion of outlie
46、rs 7777 Number of accepted results 14 14 14 42 Mean 495.0 126.4 470.0 363.8 Repeatability standard deviation S(r) 31.96 5.35 10.86 16.05 Repeatability coefficient of variation CV(r) % 6.46 4.23 2.31 4.41 Reproducibility standard deviation S(R) 51.18 34.87 61.09 49.05 Reproducibility coefficient of v
47、ariation CV(R) % 10.34 27.58 13.00 13.48 Repeatability r 95 % 2.833 S(r) 90.45 15.14 30.72 45.43 Reproducibility R 95 % 2.833 S(R) 144.83 98.69 172.88 138.804 BSI 12-1999 BS 4317-21:1999 Annex A The reported results are given in Table A.4 expressed in Brabender Units (BU). No outliers or stragglers
48、were identified. Table A.4 Results of interlaboratory tests for resistance after 45 min Laboratory no. Sample A Sample B Sample C 1 470 445 80 95 380 365 2 530 560 190 190 550 550 4 460 420 95 90 435 435 8 500 590 150 140 470 500 11 455 450 115 120 440 420 13 520 465 120 120 505 500 15 535 530 135 1
49、30 520 510 A.3.2 Extensibility The results of interlaboratory trials to determine the extensibility after 45 min are given in Table A.5. Table A.5 Extensibility after 45 min Measurement Sample A Sample B Sample C Total Number of laboratories 7 7 7 7 Number of results 14 14 14 42 Number of laboratories retained after deletion of outliers 7777 Number of accepted results 14 14 14 42 Mean 156.8 139.7 148.3 148.3 Repeatability standard deviation S(r) 5.19 3.02 5.64 4.62 Repeatability coefficient of variation CV(r) % 3.31 2.1
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