Methods of test for Cereals and pulses
BS 4317-21:1999 pdf free.Methods of test for Cereals and pulses一 Part 21: Determination of rheological properties of doughs using an extensograph.
NOTE Al] measuring equipment should be ealthrated,
6.1 E.rten.sograpk, with constant temperature water
6.2 Farinograplt, with 300 g bowl, burette and
constant temperature water circulating tank (see
6.3 Balance, at least able to weigh 300 g with an
accuracy of 0.1 g.
6.4 Plastie.s scraper.
6.5 conical flask or beaker, 250 niL.
6.8 Thermometer, graduated in intervals of 0.1 °C.
6.9 Timer, at least able to read in intervaLs of 1 s.
NOTE If the apparatus includes an integral liming device, this
should not be used for the test.
7.1 Operation of the extensograph
Turn on the thermostat and circulate the water until it reaches 30°C ± 0.5 °C. Before use, check that the temperature of the extensograph cabinet is
:io °c ± 0.5°C
Ughtly 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 nun before use.
Ensure that the chart paper is correctly aligned on the spnwkets of the chart. reronler. When the extensograph balance ann 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 arm.
7.2 Dough preparation
Allow the flour to equilibrate to 25.0 °C ± 5.0 °C if
Before carrying out the tests mix a scrap dough.
NOTE For this pupose 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.Fill the burette, including the tip, with water at
30.0 °C士2.0 °C.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.
Set the pen on a 9 ruin line on the farinograph chart paper. Start mixing 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 mm line pour the sodium chloride solution through the funnel into the bowl. Tap the funnel to release any adhering drops into tiw bowl. Add further water front 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 11(1 at the end of the mixing procedure. When the dough forms. careftilly use the plastics scraper to push any flour or dough adhering to the mixing bowl walls down into the mixture. Mix for 1 mm from the start of water addition.
After 1 ruin from the start of water addilum, switch otT (he farinograph motor and allow the dough to rest in the covered bowl for 5 mm, After the rest period, mix for a further 2 mm with the motor running at approximately 63 r/min.
NOTE 1 The fInal dough consistency should be 500 HU ± 20 Ht NOTE 2 [)unng the second mixing penod additional water may bc uided uiily to catinude the wider ukIiIton for a further mixing of (he same flour. [toughs produced under these conditions should not be siretdied as the dough structure is not uniform.
7.3 Dough shaping
Remove the dough from the mixer with niininuim han(lhng. 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 from 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 replace the dough holder in the cradle. Set the I inter to 45 nun. 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 nun 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 (he dough piece has broken, remove the dough holder from the balance ann, collect the dough from the dough holder and hook and repeat the balling and moulding operations in aecrduwe with 7.3. Reset the timer to 45 miii.
NOTE 1 With new models of exiensograpli the hook should stop auloniaflcally and return to the start pounon. With older models the hook shouki be stopped by use or a switch alier the dough piece tweaks arid to stall It returning to its upper poshion.
Measure extensibility to the point where the dough first breaks.
NOTE 2 Gcnernily one of the dough picc’ra should break before the other. II so, the point at which the dough first breaks may be ni.tde ticarer by geoLly nudging 11W t’xtensograph hahuwc ann upwards intmediately 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 dough holder and hook. Repeat the balling and moulding operations in accordance with 7.3 on the second (k)Ugh I)ieCC.
Move the pen to a fresh position on the extensograph chart. 45 mm after returning the first dough piece to the resting cabinet, repeat the stretching operation in accordance with 7.4 and 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 nun afier returning the first dough piece to the resting cabinet, repeat the stretching operation in accordance with 7.4. When the dough piece breaks, remove from the dough holder an(l 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 holder and hook and discard.
8 Expression of results
Relswt the resislanee (the mean niaxitmun height of the curves from the two dough pieces) at each test time (45 mm, 90 mm arid 135 nun) to the nearest 5 1111.BS 4317-21 pdf free download.Methods of test for Cereals and pulses