TESTING OF NEW-ZEALAND-GROWN WHEATS.

New Zealand Journal of Agriculture, Volume XXXII, Issue 1, 20 January 1926, Page 26

TESTING OF NEW-ZEALAND-GROWN WHEATS.

RESULTS FOR YEAR 1925

( Continued.)

L. D. Foster, B.Sc., Analyst, Chemistry Section, Wellington

III. BAKING TESTS

Experimental baking tests are designed to determine the actual suitability of different flours for breadmaking. In particular such tests differentiate between those flours which, though low in protein content, yet make good loaves, and those flours which, possessing a good protein content, for one reason or another fail to produce good bread. The work carried out by the Chemistry Section in 1925 has been fairly complete, and affords an insight into the behaviour of the flours obtained from the New-Zealand-grown wheats when undergoing the practical test of baking ; it also shows such correlation as exists between chemical analyses and baking tests. Some additional analytical figures, to be given in another article, will elaborate this point

To carry out baking tests accurately and efficiently, the conditions of baking must be as nearly the same in every series of loaves as it is possible to maintain them. Even baking tests, however, are not infallible, and it is not always easy to obtain absolutely concordant results. All tests, however, are done in duplicate. If, as sometimes happens, these duplicates do not approximately agree, it is then necessary to repeat tests a third and perhaps a fourth time. From an average of such a series a fairly correct idea of the breadmaking qualities of a flour may be obtained.

The method of experimental baking is standardized as far as possible. Not only must .the sugar, salt, and yeast be always of the same good quality and used in exactly the same amounts, but the mixing, doughing, proving, and baking processes must be carried out under the same conditions in every case. The only differences in treatment are the amount of water added in mixing the dough, and the length of time the dough is allowed to ferment. The amount of water added is based on the percentage absorption of water.

SIZE OF LOAF.

The size, or volume, of a loaf is a measure of the quality or strength of the flour from which it is baked. A dough will expand two to three times its original volume before it reaches its maximum expansion, the time for this depending on the quality of the flour and the activity of the yeast. In the present experimental tests the dough was allowed to reach a point just short of its maximum expansion before it was placed in the oven. It is true that in commercial baking a loaf is not allowed to ferment as long as this, but a flour .which gives the best loaf under the maximum expansion of laboratory baking tests will also make a loaf of good volume and texture when baked in the ordinary commercial way.

METHODS OF EXPERIMENTAL BAKING TESTS. A greater proportion of yeast is used in experimental baking than in commercial methods, but this is to ensure that any failure on the part of the flour to produce a good loaf is not due to the lack of yeast. Sugar is also added so that there shall be no lack of material for the yeast to work upon in the initial stages of proving. The flour, water, yeast, salt, and sugar are warmed to 35 0 C. ( = 95 & F.), and mixed. The doughs receive as nearly as possible the same amount of kneading, and are then placed in a proving-cabinet, where the fermentation proceeds under regulated conditions of temperature (35 0 C.) . and humidity. A definite degree of dampness must be-maintained to prevent the formation of skins on the doughs, which are. likely to modify expansion. The doughs are placed in wellgreased tins and allowed to attain almost their maximum expansion ; they are then placed in the oven, where they are baked at 220° C. (== 428° F.). The tins in which the loaves are baked are all equal in

side measurements, but vary in height—namely, 2 in., 2-4 in., 2-8 in., and 3-2 in. By this variation in the height of the tins it is possible to arrange all doughs, each perhaps differing in volume from the others, with the same amount projecting, at maximum expansion, unsupported above the sides of the tins. From the shape of that portion of the unsupported loaf it is possible to obtain some idea of the strength of the flour. A dough made from a strong flour . will stand up boldly; a weak dough tends to collapse and spread over the sides of the tins. ’ '

With each series of experimentally milled flours a commercial sample is included in the baking tests as a standard (see Fig. 4). The experimental, flours are compared with this, as to texture, colour, &c. The commercial sample serves also as a check on the proper maintenance of conditions in doughing and proving ; for if the standard flour gives the same volume each time it is baked one may assume that conditions of mixing, &c., have been the same in each series. After baking, the loaves are cooled, weighed, and their volumes measured on the following day they are cut in halves and their texture and colour noted.

SIZE OF LOAF AND PROTEIN CONTENT

The size of the loaf is connected, on an average, with the amount of protein the flour contains. Graph 3 shows this relationship, the average loaf-volume of the flours tested this year being plotted against the percentage of protein. To obtain these figures the flours with approximately the same amount of protein (8-9 per cent., 9-10 per ■cent., &c.) were classified together, and the average -volumes of these classes were then determined.

It will be noticed that there was a rise in average -volume for those flours containing less than 10 per cent, protein. This was apparently due to the very good quality of the gluten in the flours obtained from the Lake County wheats, which latter were low’ in protein content but made good bread.

NOTES ON RESULTS OF BAKING TESTS (SEE TABLE 6).

The flours from the various wheats are arranged in the same order as that adopted, in Table 5 in the second article of 'this series [Journal, December, 1925, p. 381), thus enabling easy reference to be made to the chemical analyses. The percentage absorption-of-water figures are

repeated, and also the percentage of protein; a description is given of the quality of the gluten as revealed by its appearance and cohesion, &c. The shape, texture, colour, and volume of the loaves are given in subsequent columns. The volumes of the experimental loaves may be compared with that of the standard loaf made from a good average baker’s flournamely, 600 c.c. Some of the loaves obtained in the baking tests are shown in Figs., 5, 6, 7, and 8. Each reproduction of the loaves has been reduced proportionally, so that any one loai in the series may be compared with any. other. »

Varieties of Wheat-flours.

The 1924 wheats were of particular interest, including as they did the flours obtained from Lake County wheats ; these Lake wheatflours were mostly low in protein, but contained gluten above the average in quality. They produced loaves of good volume, and decidedly larger than those other flours with the same protein content received in this and previous years. S 708 (Tuscan), in particular, produced a loaf of very good volume, very good shape, and fair texture and colour ; this flour compared very favourably with the best of the flours yet tested (see Fig. 9). The others from the Lake district were very little inferior to this sample.

The sample of Durum (S 392) can definitely be described as a poor breadmaking flour when used by itself (see Fig. 7) ; the quality of its gluten was poor, and it failed to make even a fair loaf, in spite of the good quantity of protein it contained. It might, however, prove suitable for blending with other flours.

The best of the 1925 flours was that obtained from .Essex Conqueror (see Fig. 5). This flour produced a loaf of excellent volume, good shape, and fair texture, a result which would be expected from its very good protein content. Scandinavian (see Fig. 5) gave the next best loaf-volume, but the texture of the loaf was poor, discounting considerably the good. volume obtained. Yeoman (Fig. 6) made an excellent loaf of good size and shape; this sample also contained a very good amount of protein of average quality. The sample of Marquis (S 769) gave a very good loaf of good shape and texture, and very good colour; one would, however, have expected this flour to produce a loaf of larger volume. Velvet

(S 771) produced a very good loaf in every respect; Snowdrop (S 772) was as good in volume, but fell off in texture and colour. White Tuscan (S 770), Hybrid W (S 778), and Velvet Ngapara (S 773) all gave good loaves. The sample of Durum from Hinds, like the Durum grown in 1924, failed to make a good loaf, though in this case it was better than S 392 (see Fig. 7). Zealand (S 776) made a medium loaf, and . one not so good as its protein content would indicate. Queen Fair (S 767) and 'Velvet (T 37) made good loaves, the Velvet sample being good in shape, texture, and colour. Marquis (T 50), from Gore,. Southland, produced a very good loaf ; the quantity of the gluten in this sample was low for such a result. The sample of Major (S 768) gave a fair loaf, as did Jumbuck (S 765) ; but Red Fife (S 777) with a protein content not particularly high, gave a loaf of very good volume, this no doubt being due to the good quality of the gluten which it contained. College Hunter’s (T 75) gave a loaf of good shape, texture, and colour, but medium in volume. Queen Fan (S 766) was a medium flour, and Solid-straw Tuscan (T 77) poor. A sample of Major (T 51), from Gore, gave a loaf of good volume ; it was fairly low in protein content. Solid-straw Tuscan (T 52) from the same locality gave a fair loaf, though it, too, was fairly low in protein content. A sample of Velvet (T 76), low in protein content, gave a fair loaf. Hybrid W (T 101) was also low in protein content, and gave only a medium loaf.

Localities.

In judging the strengths of various flours by their protein content it is fair to compare only those obtained from wheats grown under . more or less similar conditions. The flours from Lake County, however, stood out in these tests as being of very good strength even though they were low in protein content. There can be no doubt that their strength depended on something apart from the quantity of gluten present; the good quality of the gluten which they contain may have had something to do with these good baking-properties, though even here the volume of the loaf was to a limited, extent dependent on the percentage of protein in' the individual samples. The samples from Gore, (see Fig. 8) also produced good loaves and better than the protein content suggested ; none of these, however, contained gluten above the average in quality as far as a visual inspection of the gluten showed. A fairer comparison between samples could be made with the flours obtained from Canterbury wheats. Here the order of loaf-volume was, with few exceptions, the order of the protein content. The possible exceptions were Marquis (S 769) and Zealand (S 776). which were perhaps not so good as their protein content indicated ; Durum (T 78), which was decidedly poorer; and Scandinavian (S 779), Velvet (S 771), Snowdrop (S772), and Red Fife (S 777), which were better. The gluten of these samples appeared on inspection to be average in quality, with the exception of Red Fife (S 777)

SUMMARY.

Flour milled irom Essex Conqueror produced the pest loai of those varieties tested in 1925. An excellent loaf was made from Yeoman. Samples of Velvet, Marquis, and Red Fife produced very

good loaves. The Durum flours were failures in regard to their breadmaking qualities. '■ The order of the strength of the flours as determined by baking tests was, on an average, also the" order of the protein" content of the various samples. Individual protein content and loaf-volume were more closely correlated when comparing flours from wheats coming from the same wheat-growing districts. Exceptions were the flours obtained from the wheats grown in Lake County and Southland County, which generally produced better loaves than their protein content indicated. The flours from the Lake district contained gluten, above the average in quality as determined by a visual inspection of the isolated gluten these flours were milled from Tuscan wheats. Those from Southland County, however, were of average quality in this respect. Flours from Canterbury wheats gave results in which, with some exceptions noted, the protein content was a good index to the bakingvalue of the different flours.

(Series to be continued.)

BAKING TESTS.

(All figures read from left to right.)

5OO ; centimetre;

■ | Variety. Where grown. Absorption of Water. Protein. Quality of Gluten judged by Appearance. Experimental Loaf. Volume Laboratory No. Locality. County. Shape. Texture. Colour. Variety. Where grown. Absorption of Water. Protein. Quality of Gluten judged by. Appearance. Experimental Loaf. Locality. County. . Shape. Texture. Colour. . Volume 1924 Wheats. C.c. Per Cent. Per Cent. Fair Fairly good Good Fair Good Medium . . Fair — S 392 Z924 Wheats. C.c. 1 Per Cent.lPer Cent.* Fair Fairly good Good Fair Good Medium . . Fair S 392 S 709 S 709 S 712 S 712 S' 708 708 S 711 S 711 S 71.0 Durum Tuscan . . ■ • . Arrowtown Gibbston. . Lake 56-0 54'2 53'2 53-6 II-8l n-75 9-38 8-69 Poor Fair • . . Good Poor Good Fair ' . . Verv good 440 660 660 700 Arrowtown 56-2 8-56 Medium . . Good Medium . . 670 ■ Hunter’s . . Velvet .. Miller’s Flat 56-6 8'50 ,, Poor >* 620 S 710 s 713 Durum Tuscan Arrowtown Gibbston. . Lake 56-0 54'2 53’2 53-6 n-8i n-75 9-38 ! 8-69 Poor Fair Good Poor Good Fair Verv good 44° 660 660 700 Arrowtown 56-2 8-56 .. . . Medium . . Good Medium . . 670 Hunter’s . . Velvet Miller’s Flat 56-6 8-5° ’ ,, • • I Poor >> >> • • 620 s 713 S 714 Tarrasr .. Ardgour .. Vincent .. 50-8 54'6 1 7-69. 7-19 Good Good .. Good 650 . I9 2 5 Wheats. Medium . . S 714 s 774 Tarras Ardgour .. Vincent .. 50-8 54'6 7-69 7-19 .. 1 Good Good Good 650 I 9 2 5 Wheats. Medium . . Very good Medium . . Good Medium . . Good Fair Good S 774 S 775 S 775 769 S S 769 S 779 Essex Conqueror . . . Yeoman Marquis .. . . Scandinavian Velvet .. Snowdrop . . White Tuscan Hybrid W . . Velvet Ngapara Durum . . Zealand Queen Fair Velvet Ashburton Ashburton 51-4 ( 14-69 Medium . . Good Fair . . 755 48-0 49'6 48-2 50-0 14-19 13-75 13’75 i3’5 6 Fair Medium . . Fair Medium . . Good Fairly good Good Poor Very good Very good Medium . . Good 700 660 720 700 s 779 771 S 771 S 772 S 772 S 770 S 770 778 778 S 773 S 773 78 T 78 T S 776 S 776 767 S 767 T 37 Hinds . . 47-6 49'8 47-6 . 50-8 51-6 I3-5O 12-25 n-88 n-88 ii-8i Medium . . Fair Medium . . Fair Medium . . Medium . . Good Poor Medium .. Fairly good Good Medium . . Medium . . Good .. Fair 700 670 660 670 540 Ashburton Lincoln . . Springs _ . . 5°'4 52'8 50-0 11-63 11-31 11-13 Fair Good Fair Good Good Fairly good Good Good . 59° 640 650 T 37 T 50 Essex Conqueror Yeoman Marquis Scandinavian Velvet Snowdrop . . White Tuscan Hybrid W . . Velvet Ngapara Durum Zealand Queen Fair Velvet Ashburton | Hinds Ashburton Lincoln . . Ashburton Springs . . 51'4 48-0 49'6 48-2 50-0 47’6 49'8 47'6 5150’4 52'8 50-0 14-69 14-19 13’75 13-75 I3-56 I3-5O 12-25 n-88 n-88 1 r-8i 11-63 ii-3i 11-13 Medium . . Fair Medium . . Fair Medium . . Fair Medium . . Fair Medium . . Fair Good Medium . . Good Medium . . Good Poor Good Fair Good Fair Fairly good Good Poor Very good Medium . . Fairly good Good Medium . . Good Fairly good Good 755 700 660 720 700 700 670 660 670 540 590 640 650 T 50 768 S S 768 s 765 S 765 S 777 S 777 T 75 T 75 S 766 S 766 T 77 T 77 T 51 T 51 T 52 Marquis Major Jumbuck . . Red Fife .. ■ • College Hunter's . . Queen Fan Solid-straw Tuscan Major Solid-straw Tuscan . . Gore Ashburton Gore , /.. Southland Ashburton Southland 54’4 50'0 6o-8 51’6 51’4 48-8 52'4 55'2 54’4 ro-88 10-75 10-69 10-56 10-31 10-31 9-69 9-63 9’44 Good Medium . . Fair . . Medium . . Fair Medium . . Good Fair Good Very good Good Medium . . Poor Medium .. Fair ’ Medium .. Good Fair 600 600 680 560 57° 535 680 640 T 52 T 76 Marquis Major Jumbuck . . Red Fife . . College Hunter's Queen Fan Solid-straw Tuscan Major Solid-straw Tuscan . . Gore Ashburton Gore Southland Ashburton Southland 54’4 50-6o-8 5151’4 ’ 48-8 52’4 55'2 54’4 io-88 10-75 10-69 10-56 10-31 10-31 9-69 9-63 9’44 Good Medium . . Fair Medium . . Fair Medium . . Good Fair Good Very good Good Medium . . Poor Medium . . Fair Medium . . Good Fair 600 600 680 560 57° 535 680 640 76 T College Velvet .. Hybrid W . . Ashburton Horrelville Ashburton .Eyre • 51-8 49'4 9-25 8-75 Medium . . ,, 5S0 T 101 College Velvet Hybrid W . . Ashburton Horrelville Ashburton Eyre 51'8 49’4 9’25 8-75 Medium . . !so

Table 6.-Baking Tests.