A METHOD FOR DETERMINING THE QUALITY OF GLUTEN IN WHEAT

Abstract: The quality of gluten in wheat is determined by centrifuging a gluten sample taken from a wheat dough against a sieve. Upon completion of the centrifugation process, it is determined how large a proportion of the sample has remained in the sieve, without penetrating therethrough. The magnitude of this proportion is used as a measurement of the gluten quality.

Description: A method for determining the quality of gluten in wheat The present invention relates to a method for determining the quality of gluten in wheat, in which method a. gluten sample taken from wheat dough is placed on a sieve in a centrifuge and centrifuged against the 5 sieve. • ••' When determining the quality of wheat flour,, it is normal to establish the amount. of protein and' gluten ■ contained therein. This can be achieved with the aid of relatively simple methods which can be quickly carried 10* out.. This analysis alone, however, is not sufficient '. ■ "to assess the baking properties of the flour with any "' • • degree of surety, since two flours which have mutually '■ the same protein or gluten content may have totally ■ • ■ ■ . different baking properties, due to the fact that they 15 have* utually different gluten properties. There is a great need to be able to establish the gluten quality in .wheat iri- a simple and reliable manner, this need . being found particularly among wheat growers, millers and bakers. 20' When determining the gluten content* of wheat ' flour, it is normal practice to prepare a wheat dough from a given quantity of wheat flour and to remove the , ' . starch from the dough, by treating the dough in a jet of water. This procedure results in a residual product 25 of water-insoluble, wet gluten which contains 80-8555 protein. A measurement of the gluten content of the flour can be obtained by weighing the gluten making up the residual product. Since the gluten content an the protein content are mutually proportional, there is. ' 30 also obtained in this case a measurement of the protein content of the flour. It can be ascertained manually that the proper¬ ties of the gluten obtained in this way may vary from flour to flour. . • • For example, the gluten can be dry, elastic, .inelastic, short, stretchable, slimy, tacky, etc. Manual characterization of the properties of the gluten is not considered to give a sufficiently reli- 5 .able and clear result. There is, however, no inter¬ nationally accepted method for determining gluten quality analytically. • Many different types of apparatus have been - . ' constructed for measuring the rheological, i.e. 0 elastic, plastic and'.viscous properties of the gluten. • One type of apparatus is based on the method of measuring the stretchability of the gluten when ■ ■ _ • subjected to ' a-'g . iven force over a given period of time. Another type ' of apparatus is based on the method 15 of. first subjecting the gluten to a given force over a ., given period of time .and then measuring restoration of the gluten to its original state. Another type of apparatus is based on the method of placing a gluten sample between a plate and a cone, subjecting the 20 . ■ sample to torsional forces, and measuring the relaxa¬ tion properties of the sample. None of these apparatus, •however, has found general use, due to the fact that the methods supp.lied therewith are too complicated and '■ • ' . the apparatus too expensive. 25 In certain countries, e.g. Austria, the • swelling-index method (German: Quellzahl) is used Officially .to determine the gluten quality and baking properties of wheat flour. This method is based on degrading the gluten in- la'ctic acid and recording the 30. .. degradation effect. The method is both complicated and highly time consuming (3-^ hours are required in. order to ' carry the method into effect). The object of the present invention is to enable the quality of gluten in wheat to be determined analy- 35 tically in a simple and positive manner. This object is achieved in accordance with the invention by determining the amount of gluten which penetrates the sieve under the influence of the centri¬ fugal force generated, and using this penetrative ;5 amount .as a measurement of the gluten quality. More particularly, subsequent to centrifuging the sample there is determined the ratio between the amount of •gluten which has. not passed through the sieve and the ' * ; • total amount of gluten present. 10 ' . A particular advantage is afforded in this regard when the extent to which the gluten sample passes through a special sieve is determined in combi- • ' ■ • nation-with the centrifugation process normally .carried out to determine the gluten content of flour, e.g. With- 15 the. aid of. an apparatus Glutomatic manufactured, by . ■ Falling Number. AB in Sweden. The only additional working procedure that need be carried out in compari¬ son with the known procedure is that of weighing the. portion of the gluten! sample located on one side or • 20 • . the other of the sieve. Further features of the invention and advantages •- ' ' • •"'afforded thereby will be apparent from the following' description and claims. .. ;. ' • ; The invention will now be described in more 25. • '• ■ detail with the aid of an exemplifying embodiment ' thereof illustrated in the accompanying drawings, • in which Fig. 1 is a schematic view from above of test apparatus for carrying out the method according to 30 • the invention; ' Fig. 2 is a perspective view of a sample container used in Fig. 1; Fig. 3 illustrates a part of the sieve incorporated in the sample container, and 35 Fig. 4 is a diagram which shows the relationship between Quellzahl Q and gluten index for various gluten samples. For the purpose of determining the quality of the gluten in wheat there is first prepared a dough from a given amount of wheat flour, and the dough is washed under a jet of water so that the water-insoluble 5. part of the dough remains, this residual product con¬ sisting of. et gluten. The separation of the gluten can be achieved readily and simply with the aid, e.g. of - an apparatus Glutomatic manufactured by Falling Number - • • ' • ' . AB in Sweden. . ' '• ' 10 This apparatus includes a centrifuge for removing excess water from the wet gluten. The normal practice hitherto has been to place the wet gluten • against a sieve in the centrifuge and to subject the • gluten to centrifugation, whereafter -the gluten is • 15 collected and weighed in order to determine the gluten ■ content of the flour. It has surprisingly been found ■ in accordance with the invention, however, that this centrifugation can be utilized not only to determine the gluten content of the flour, but also to determine 20: ' the .quality of the gluten analytically. Experiments- have shown .that there is a direct .'relationship between gluten quality ' and the ' ability 'of . the gluten, sample to pass through the sieve under the influence of. centrifugal force. The extent to which the 25 sample penetrates the sieve can be established* easily,- by weighing, for instance, the amount of gluten which ' does not pass through the sieve in addition to weighing the total amount of gluten in accordance with the earlier known procedure. Thus, it has been found that 30 the method, applied at present to determine the gluten content can be readily complemented in a manner which will also enable the quality of the gluten to be deter¬ mined at an insignificant extra cost and with but a negligible amount of additional labour. Fig. 1 illustrates how, in accordance with the invention, a conventional centrifuge 1 of the kind used in the aforementioned apparatus Glutomatic is used to determine both the gluten content and the gluten 5 quality at one and the same time, with the use of the wet gluten obtained when washing wheat dough in a conventional manner. The centrifuge 1 has a wall radius R of ca 60 mm and a working spe.ed n of ca 6000 rpm and ' . rotates in the* direction indicated by the arrow 2. 0 Arranged in*the .centrifuge 1. ar.e two mutually identi¬ cal, substantially tubular gluten sample containers 3 and 3'. Each container, has a. sieve-f.ormi.ng partition •• wall. which during the process of centrifugation is. located- at a distance. r_ of ca.49 mm from the ' centrifuge 5 centre and is provided with a large number of holes 5 - •■ . ' ; of diameter d_. which have a mutual spacing t_ - (see Fig 3). rior to centrifugation, a gluten sample 6 is placed on the side of the sieve 4 facing the centre of the centrifuge and during. the centrifuging process 0 .. ' part of the sample will be forced through the sieve 4, so that upon ' completion- of the centrifugation process ' • an inner sample part 6' will ' be located inwardly of ■ •; the -sieve and an outer sample part 6" will be located outwardly thereof.• The proportional relationship -5 ' , ' between either one , of the sample, parts 6' and 6". and the whole of the sample 6 can be readily determined by . weighing said sample- part and said whole sample, and has been found to constitute a measurement of the quality of the gluten. 0 It. will readily .be understood that a given type of gluten will penetrate the sieve, to varying degrees, depending upon the magnitude of the centri¬ fugal force generated- (a function of the speed ri and the centrifuging radius r_) , the length of time over 5 which the sample is centrifuged, and the sieve con¬ struction. It has also been found that the waiting time prior to centrifugation plays a signficant part in the extent to which the gluten penetrates the sieve. The extent to which the gluten penetrates the sieve increases with increasing centrifugal force and 5 increasing centrifuging time, and also with increasing mesh- size. ■ If,- however, different sorts of flour are tested " under the same conditions, i.e. at mutually the same .. ' • . centrifugal 'force and ' are centrifuged for' mutually the 0 same length of time with the aid of one and the same sieve and with the same waiting period prior to centri- " ' ' fugation, it is possible to graduate the quality of the gluten in the various flour ■ sorts .on the basis of the measured- extent of penetration through the sieve. 15 -The tests can be made more revealing or indica- ■ ' tiv ' e within certain, quality intervals, by changing the test conditions. For instance, by using a coarse sieve it is easier to measure differences in quality between such., gluten- samples that when using a fine sieve, would • 20 , show only small differences, due to. the fact the samples find it difficult to pass through a fine sieve, this' ay be of .particular interest in those areas of the quality scale in which the limit between bake- ability and non-bakeability for the flour concerned 2i5 • - is located. ' Table I below recites the test results obtained in the case of various flours, ' where the samples were centrifuged for 1 minute at a centrifuge speed n. of 6000 rpm.,' and a distance from the centrifuge centre 30 ■ of 49 mm. Two different sieves were used,- the one with d=0 r 60 mm and t=l,40 mm, and the other with d=0,75 mm and t=l,50 mm. The waiting time prior to centrifugation was ca one minute. Table I. Wheat flour • Gluten content Q o Q 30 Gluten index d= d= 0,6mm 0,75mm gluten index.,. It will also be seen that the gluten index for a given wheat flour will decrease with increasing hole sizes in the sieve. ' 30 , , Fig.' 4 illustrates graphically, on the basis of Table ' I,, the relationship between, gluten index and . "Quellzahl" Q Q . It will be seen from this graphic illustration that there is a clear relationship between gluten index and. Q Q . Thus, it is possible to obtain 35 a measurement of the gluten quality on the basis' of the gluten index. In some countries the law requires the gluten to have a Q of at least 14 in order to have acceptable baking properties. In Fig. 4 this corresponds to a gluten index of at least ca 60 with a sieve having a 5 . hole diameter of d=0,6 mm. Different test series have shown ' that the reprodueibility is good. A sample container 3 of the illustrated kind has. been, found particularly, suitable for manipulating • the gluten .sample,- hich is prevented from- spreading 10.- in. the ' circumferential- direction of the centrifuge by the walis surrounding the sieve.. This greatly facili¬ tates collection and -weighing of the sample parts. The . . ' . ' -. . -configuration of the sample -container and its position- ; ' - ing. in the centrifuge can, ' of course, be varied in 15- many " different ways. ,For .example*,-.-the number of. sample ' ' containers, used may " -be " varied in accordance with requirements, while taking into consideration the " problems of balance in the centrifuge. For the purpose of determining the influence of 20 the Waiting .time of the gluten sample on . the gluten ' ' index,, a- sample can be centrifuged several times. For ■ • ' example, • the.sample can be centrifuged after a waiting time of one ' inute an.d then centrifuged. again after a further waiting time of e.g. 30 minutes. By centri- 2.5 . fuging the whole s.ample each time, it is not necessary. ■ to divide the sample down into smaller portions, ' although the sample can be- divided-up, of course, if so desired. Those, experiments carried out hitherto have 30 shown, that the gluten -quality of wheat flour can be : . determined in a very reliable and ' very simple manner with the aid of standardized testing procedures.

Claims: CLAIMS 1. A method of determining the quality of gluten in wheat, in which method a gluten sample taken from a wheat dough is placed on a sieve in a centrifuge and centrifuged against -the sieve, characterized by deter- mining ' the' extent to which the gluten sample penetrates the sieve under the influence. of the centrifugal force generated artd taking this extent of penetration as a measurement of the gluten quality,. 2. A method according to Claim 1, characterized by determining the ratio between the amount of gluten ' , ' that has not penetrated through the. sieve and the total atnount of gluten, 'upon completion of the centrifugation process. 3. A method according to Claim 1 or 2, characterized by performing the centrifugation at a pre-determined centrifugal force-. 4. A method ' according to Claim 3, characterized by using a centrifugal speed of ca. 6000 rpm, and by locating' the sample at a maximum distance from the ' . ' • '' centre of . -the-centrlfuge of "ca 60 mm. 5; A method accprding to any of Claims 1-4, . characterized by continuing the centrifugation process "over a pre-determined length of time. 6. ' A method according to Claim 5, characterized by continuing the- centrifugation process for ca one minute. '• 7. A method according to any of Claim 1-6, ' characterized by using a sieve of pre-determined . properties. 8. A method according to Claim 7, characterized in that the sieve has the form of a perforated plate in which the hole diameter is ca 0.6 mm and the hole spacing is ca 1.40 mm. 9. A method according to any of Claims 1-8, characterized by placing the gluten sample on a sieve which is provided with circumferential walls on both sides thereof. ; " 5 10. A method according to any of Claims 1-9, characterized by commencing the centrifugation process subsequent to the lapse of a pre-determined length of time from the time of obtaining ' the gluten sample, suitably a time lapse. of one minute. ] _0 ' ■ , ' 11. A method according to Claim 10, characterized by centrifuging the gluten sample for at least a second time, suitably subsequent to a time lapse of* 30 minutes from ;the time of completing the first centrifugation process.

Inventors: PERTEN HARALD, PERTEN, HARALD
Applicants: PERTEN HARALD, PERTEN, HARALD
Application year: 1987
Main classification: G01N33
IPC codes: G01N11, G01N19, G01N33