764 BENNETT d COPPOCK-FLOUR TESTING. I I

Nevertheless, these comparative tests have enabled us to interpret the results on each They reveal the factors involved in selecting test procedures and instrument more accurately.

the pitfalls which can occur in their application and relation to baking behaviour.

British Baking Industries Research Association Chorleywood

Herts. Received 27 January, 1956

References 1 Aitken, T. R., Fisher, N. H., & Anderson, J. A.,

a Bennett, R., & Coppock, J. B. M., J. Sci. Fd Agvzc.,

4 Bennett, R., & Coppock, J. B. M., Trans. Amev.

6 Near, C., &Sullivan, B., Ceveal Chem., 1935. 12,527 8 Dempster, C. J., Hlynka, I., t Winkler, C. A..

7 Amos, A. J., Analyst, 1949, 74, 392 * Hlynka, I . , & Bath. F. w., Cereal Chem., 1955.32,

Cereal Chem.. 1944, 21, 465 ; 1944. 211 489,

1952, 3, 297 Ceveal Chem., 1952, 29, 39

Halton, P., Ceveal Chem., 1949, 26, 24

Ass. Ceveal Chem., 1953. 1 1 , 172 472

FLOUR TESTING. 11."-An Alternative Method of Using the Brabender Farinograph and Extensograph for Testing Bread Flours

By RUTH BENNETT and J. B. M. COPPOCK

A method is described for measuring the water absorption of flour, using a yeasted dough 3 hours after mixing, by determining the minimum mobility on remixing in the Brabender Farinograph. This enables a correction to be applied to derive the water neces- sary for the dough subsequently stretched on the Extensograph. A yeasted dough is given 3 hours rest before moulding and then a further 30 minutes before stretching. The advan- tage over the standard method is that untreated and variously treated bread flours are shown in a more correct relation to each other in close agreement with their placings in baking practice.

Introduction The standard method suggested by the makers of the Brabender instrument is used in many

laboratories for flour testing. I t gives useful information on the strength of different wheat flours especially on untreated flours before receiving bleaching and/or oxidizing treatment.

If, however, this method is used for testing bread flours from mixed grists that have been treated with various ' improvers ', the type and amount of which is not known by the operator, then in certain cases misleading results can be obtained.

In Part I' are described the factors involved in improving the response of the Brabender instrument to oxidizing improvers and in particular to potassium bromqte.

The defects of the standard method principally lie in : (a) the measurement of water absorp- tion by resistance to mixing on the Farinograph in which dough stickiness increases resistance. A sticky dough causes the water absorption determination to give a misleading and too high water requirement of a flour in relation to the water desirable for satisfactory baking into bread ; (b) the water absorption, being measured at the mixing stage, takes no account of dough soften- ing during the fermentation process. It is essential in making good bread that dough con- sistency should be correct at the dividing and moulding stage, i.e., the time that the dough is tinned prior to proving and baking ; (c) the Extensograph stretching test being given insufficient time in the dough fully to reveal the effect of certain flour treatment ; and (d) the absence of yeast so that a dough made from unbleached and untreated flour reveals little change with time.

* Part I : preceding paper

J. Sci. Food Agric., 7, December, 1956

BENNETT 6. COPPOCK-FLOUR TESTING. I I 765

Thus the essential requirements in overcoming these difficulties are (I) inclusion of yeast in the dough (see Fig. 2, Part Il), (2) measurement of water absorption at the end of a fermenta- tion period and (3) moulding of the dough after fermentation and prior to its stretching. These factors are included in the Simon method previously described and as originally devised by Halton.2

A method has now been devised using the Brabender equipment, to meet these requirements.

Experimental Method

The following equipment additional to the standard instrument is required : (I) Jars with lids to hold 450-500 g. of dough and sufficient space to allow for its expansion

For this ~z-in.-high glass jars as used for storing boiled sweets,

(2) A fermentation cabinet maintained a t a constant temperature for holding these doughs. The same amount of salt and yeast as used in commercial baking should be present in the

dough. The temperature of the fermentation cabinet should be equal to the average fermentation conditions in the bakery. A typical basic method would be to prepare a dough from flour 300 g., salt 4'5 g., yeast 3.75 g. equivalent to a mix of 280,4*2 and 3 3 lb. respectively, fermenting at 27" for 3 hours after mixing with the appropriate quantity of water,

Water absorptio?z.-A dough is mixed in the Farinograph for 3& minutes adding an amount of water (calc. on the weight of flour) approximating to the correct amount, e.g., 55% for flour in England and Wales (15.4 gallons per sack) ; 57% for flour in Scotland and Northern Ireland (16.0 gallons per sack) ; 50% for flour in Eire (140 gallons per sack). The quantity of water added should be noted.. The dough is then left in a covered jar at 27" for 3 hours to ferment.

450 g. dough are then weighed and remixed in the Farinograph until the minimum mobility (the lowest part of the curve) has been just passed. The centre of the curve at this minimum mobility is read off in Brabender Units (B.U.). From the consistency of the dough in B.U. and the water known to have been given to this dough, the correction in this amount of water to give dough of standard consistency (510 B.U.) can be found from Table I. This table shows

during 3 hours' fermentation. etc., are convenient.

Table I Correction table for converting water given to required water absorption at standard consistency

3 h. B.U.

650 640 630 620 610 600 590 580 570 560 550 540 530 520 510

Water to be increased by 3 h. Water to be decreased by yo of gallon per B.U. yo of gallon per

flour wt. sack flour wt. sack 3'6 3'4 3.2 2'9 2'7 2'4

1.8 I .6 1.3

0.8 0.7 0.4

2'0

I '0

1'0

0.95 0.9 0-8 0'75 0.7 0.6 0.55 0.5 0.4 0.3 0.25 0'2 0' I -

0'1

0.5 0.8

1;4 1'7

2'5 2'7 2'9 3'0

1'1

2'0

Note : 55% dough water = 15.4 gallons per sack (280 Ib.) 57% 1 ) ., = 16.0 ,, ,, .. ., ,, 50% ,, . ,, = 14'0 ,, ,, ,,

0.05 0.15

0.3 0.4 0.5 0'6 0.7 0.8 0.85 0.9

0.2

the amount of water to be added to the amount actually given, for each B.U. above 510, and similarly to be deducted from the amount given if the reading is below 510. If the water selected for actual test is more than 3% (I gallon per sack) different from that required for a consistency of 5x0 B.U., a repeat test should be made, giving dough water nearer the correct figure.

J. Sci. Food Agric., 7, December, 1956

766 BENNETT 6. COPPOCK-FLOUR TESTING. II

The table was originally prepared by taking several types of flour and preparing doughs from each at five or six different levels of water, and measuring consistency after 3 hours. Con- sistency in B.U. was plotted against the known water given. From a graph representative of these several tests, the values in the table were read off.

Water absorption levels obtained in this way have been found to agree closely (a) with the baker's opinion of the requirements of a flour and (b) with the figure obtained by extrusion on the Simon Meter.

As each Farinograph may have slightly different correction factors from those given, con- struction of individual correction tables is advisable. It should be stated, however, that closely similar figures have been obtained on another instrument.

Extensograph.-A dough is prepared containing the amount of salt and yeast stated above, and the quantity of water obtained from the water absorption test. The dough is fermented for 3 hours in a covered jar a t 27'.

Two 15c-g. pieces are weighed, moulded and shaped in the usual way, and allowed 30 minutes' resting at 27" before stretching in the usual manner. (If preferred 45 minutes' resting can be allowed, but the shorter resting time permits the performance of a greater number of tests per

Further information on flour quality can be obtained by fermentation tolerance tests. In this method the dough is divided after a I-hour fermentation in the jar and is then moulded and stretched 30 min. later. Each dough piece is pressed together by hand and returned to the constant-temperature cabinet of the Extensograph until 2 hours after mixing, when the process is repeated, and again at 3, 4, 5 hours, etc.

The ratio of extensibility to resistance gives a useful guide to fermentation time require- ments, the larger the ratio the longer the fermentation time necessary to give the best bread.

Example Water absorption.-If 55% water (15.4 gallons per sack) was used in doughing and gave a t

3 hours, on remixing, a minimum mobility figure of 550 B.U., to this 55% is added an additional 1.0% (0.3 gallons per sack) giving a ' correct ' water absorption of 56% (or 15-7 gallons per sack).

Extensograph.-To illustrate how this method gives more reliable information than the standard method two sets of tests are quoted. (I) An untreated flour, a gas-treated com- mercial flour and the untreated flour with additions of potassium bromate and ascorbic acid at levels adjusted to give equivalent bread to the commercial treatment, were all baked, tested by the standard method and also tested by the suggested procedure. Extensograph curves and breadprints are given in' Fig. I. It can be seen that in the standard method the three treatments give very different curves, contrary to the baking behaviour of these flours. The suggested method, with yeast in the dough, gives curves that can be more directly interpreted to baking behaviour.

(2) An untreated and a commercially treated flour were each baked allowing I, 3 and 5 hours' fermentation before dividing and moulding and were each tested by both the standard and suggested methods at these same times. Breadprints and Extensograph curves are given in Fig. 2. I t is seen from the breadprints that the untreated flour gives progressively improving bread up to 5 hours, whereas the treated flour gives better bread than the untreated flour a t 3 hours, but poorer bread at 5 hours.

In the standard method without yeast, the untreated flour shows no such progressive change as is evident in the bread. The treated flour shows some change, when tested by both methods. A comparison of the two loaves baked at I, 3 and 5 hours, respectively, with the corresponding Extensograph curves at I, 3 and 5 hours indicates the closely parallel changes revealed in the suggested method that are not indicated by the standard method.

The replication of the procedure is satisfactory: for example, (I) using yeasted doughs 3 hours after fermentation, Extensograph curves on duplicate dough pieces agree as well or better than those for the unyeasted doughs on the standard method ; (2) a series of flours each tested in triplicate on the same day gave a variation between triplicates in resistance of 20-30

J. Sci. Food Agric., 7, December, 1956

day 4

The suggested method, however, does show this change.

BENNETT & COPPOCK-FLOUR TESTING. 11 767

UNTREATED GASEOUS 00025 % 00025% COMMERCIAL BROMATE ASCORBIC TREATMENT ACID

0.0025 X ASCORBIC ACID

GASEOUS COMMERCIAL

STANDARD METHOD SUGGESTED METHOD

FIG. I.-Untreated pour and $our treated with bromate and ascorbic acid equivalent to commercial treatment. Comparison of the standard 135-min. Extensographs with the suggested method with yeast at 3 hr. The curves are

f normal size - I HOUR- -3HOURS+ -5 HOURS- UNTREATED TREATED UNTREATED TREATED UNTREATED TREATED

UNTREATED

NO YEAST

WITH I h.

FIG. 2.-Untreated $our and commercially treated flour. Comparison af Extensograph tests with and without yeast at I, 3 and 5 hours, with bread baked after I , 3 and 5 hours

units and extensibility of I unit ; (3) no larger variation was obtained on replicates tested on different days during a period of about a month.

British Baking Industries Research Association Chorleywood

Herts. Received 27 January, 1956

References 1 Bennett, R., & Coppock, J. B. M., J. Sci. Fd Rgvic., Halton, P., Cereal Chem., 1952, 3, 297

19.56 7 , 754

J. Sci. Food Agric., 7, December, 1956