TESTING OF NEW-ZEALAND-GROWN WHEATS.

New Zealand Journal of Agriculture, Volume XXVII, Issue 1, 20 July 1923, Page 1

TESTING OF NEW-ZEALAND-GROWN WHEATS.

I. MILLING-QUALITIES.

L. D. FOSTER,

Analyst, Chemistry Section

TN the growing of wheat, however much maximum-quantity IN production may be aimed however much maximum-quantity production may be aimed at, it is the quality of the flour produced from the wheat which is of most value to the miller and the baker, and incidentally to the consumer. A good milling-wheat is one which produces the greatest quantity of flour of . the best quality. Hence, being of good quality, or “ strength ” as it is called, ’ such wheat is in greater demand, and consequently should bring a higher price.

Wheats, however, are often valued by their general appearance, weight per bushel, soundness, &c., and bought according to these valuations, not so much attention being paid to their capacity for-producing large'amounts of flour of good quality. As a matter of fact, good appearance is often associated with “ weakness,” and weight per bushel is not a sure indication of.strength. And although, where these facts are taken into consideration, large yields are often associated with inferior strength, it should be remembered that it has been found possible in many countries to find and develop varieties especially suited to particular districts yet sacrificing little of yield to strength.

STRENGTH IN FLOURS.

It may be advisable at this point to state as exactly as possible what is meant by “ strength.” Biffen (i) defines it most satisfactorily as follows :. “A strong wheat is one which yields flour capable of making large well-piled loaves.” Wheat-flour has the property, in common only with rye-flour, of forming when mixed with water a dough which produces, on leavening and baking, a porous bread. This is due to the gluten it contains being able to imprison in small bubbles the gas generated by the fermentative action of yeast. Upon the quantity and quality of this gluten present in the flour its strength largely depends. A strong wheat - flour produces a loaf of larger volume than that produced by a weaker flour.

Flour, as a foodstuff, consists of about 70 per cent, of starch and 10 to 12 per cent, of proteins. These latter are highly complex compounds, for the most part non-crystalline in form. They are assimilated by the body, and furnish that constant supply of energy so necessary to life. Starches are heat-producing substances, while proteins are largely tissue-forming and contribute to the formation of muscle, &c.

One of the oldest methods of determining strength is the separation and weighing of gluten in flour. Gluten is a protein substance, and certain other proteins are associated with it in small amounts. Generally speaking, it may be said that with all grades of flour the higher the percentage of protein the greater the strength to a certain point (3) ; there is also a very close correlation between the protein in the flour, the quantity and quality of the gluten, and the loaf volume (4, 5). It is well known that there are exceptions to this relationship, but by examining a sufficient number of samples it should be possible to discover and isolate any exceptions to the general rule. Protein content, then, is an important factor in determining strength. Other factors which must be taken into consideration, however, are the volume of water absorbed, the amount of ash present, and the ratio of wet to dry gluten (8).

As regards the amount of gluten present, its quality and other physical properties, many of our locally grown wheats have been found to compare favourably with the strong and medium-strong wheats grown in Australia and North America. In this article, however, it is intended to deal only with the milling-qualities of New Zealand wheatsv. ' ■

CAUSES OF VARIATION IN STRENGTH.

The various influences determining the strength of wheats may be divided into three classes — climate, soil, and. variety. It is well-nigh impossible to modify climate ; as regards soil-fertility, it may be said that this is rarely a limiting factor in the growing of strong wheats (1, 6) ; there remains the varietal factor. One has but to turn to the monumental work of W. Farrer in Australia and R. H. Biffen in England to realize the importance of variety. Summed up, it may be said from their work that while the quality of some wheats may change considerably with' climate and soil, there are other varieties in cultivation which retain their strength under all conditions. Thus in England the soft wheats grown at the beginning

of the century are being replaced by relatively strong wheats capable of again competing in quality with the imported varieties (2). In Australia the quality of wheats has been advantageously affected by the work of Farrer. It should be possible, then, to adopt in every wheat-growing locality in New Zealand, each with environmental conditions peculiar to itself, some variety which will yield well without at the same time unduly sacrificing quality to quantity. That this is so is apparent from the results tabulated in this and an article which will follow. ; -

The miller has constantly to watch the quality of the flour which he is marketing. His is not the straightforward task of simply milling each wheat as it arrives, but rather must he consider the price which his flour will fetch in relation to the first cost of the wheat and to the cost of manufacture. A flour is judged largely by («) colour, (b) strength, and (c) weight of flour per bushel of wheat.

No one wheat may satisfy all these requirements ; moreover, reliable wheats may vary even from season to season. The miller, therefore, by a system of blending, mixes, say, a strong wheat with one of good colour, and in this way endeavours to maintain a sufficiently high standard wherein the best qualities of each are effectively represented.

EXPERIMENTAL WORK BY THE CHEMISTRY SECTION

Work has been recently carried out by the Chemistry Section of the Department of Agriculture with the object of ascertaining the milling-yields of varieties of wheats from different localities in New Zealand and the strengths of the resulting flours. Samples were obtained through the various Instructors in Agriculture.

The milling tests have been carried out by means of the Allis Reduction Machine installed in this Laboratory two years ago (see Journal, November, 1920, page 249). This is the type of machine used largely in the United States by the different State Agricultural Departments, and also in some of the larger private laboratories. The process as actually carried out on a commercial scale is followed here as closely as possible. Duplicate results to within 0-2 per cent, are obtained; and, though, for obvious reasons the actual milling figures may differ'slightly from those obtained commercially, it is considered that the ratios of milling tests obtained are strictly comparable. It may be noted in passing that the results obtained in this Laboratory compare closely with those of the -experimental mills of both the New South Wales and Queensland Departments of Agriculture (7).

These wheats have been classified" as “ good ” and “ very good ” only when the amounts of flour obtained on milling have equalled those of a similar classification adopted in New South Wales.

Reviewing the tabulated statement (page 4), it will be seen that four samples of Pearl from various localities are given. The first three may be classified • as very good with yields of over 75 per cent., while the remaining sample is a good milling-wheat. The wheats yielding good percentages of flour come from widely separated districts. Although the number of samples, of the varieties milled in 1922 was rather small, there is a fair indication that Pearl yields as a rule a large amount of flour.

Of the nine samples of Velvet shown, three yielded very good amounts of flour, the one from Lincoln being excellent. The other samples produced good . percentages of flour. On the whole the millingqualities of Velvet are good, ranging from medium to excellent, with a good proportion of good and very good samples. It may be said that for the most part the better flour-yielding Velvet samples

come from the more southern districts. A notable exception to this, however, is the excellent amount of 75-2 per cent., obtained from the selected Velvet variety grown at Lincoln (0 812). A fact worthy of notice is that the commercial sample of the same variety grown in the same locality (0 814) gave 70-8 per cent, of flour.

The sample of Hunters grown at Killinchy yielded a good percentage of flour. College Hunters samples were received from different localities in the South Island. Of the samples milled, as shown in the table, one may be classified as very good, and three as good. The sample: from Dumbarton gave the very good yield of 73-6 per cent, of flour, and one from Airedale 73 per cent. These samples, which came from widely distributed districts, do not show any very marked differences in their milling-yields, except that College Hunters grown at Dumbarton and Airedale gave better results than those from the other districts examined' in 1922. Of this variety as a whole it may be said that for the year in which these samples were grown it yielded on the average a medium amount of flour.

Three samples only of Tuscan were received, a number too small to give much positive information ; of these three, however, two from -Lake County produced good percentages of flour — 72-6 and 71-5 respectively. White Tuscan is represented by two samples which gave good yields of flour—72-2 and 71-5 per cent. The first of these was also from the Lakes district ; the other was grown at the Winton Experimental Area. Better results were obtained from Solid-straw Tuscan. Of the samples tested, three (from North Canterbury) gave very good yields of flour, and one (from Southland) was classified as good. From"-these results it may be fair to say that in 1922 Solid-straw Tuscan gave generally z a good yield of flour. Purple-straw Tuscan is represented by a sample from Greendale, Selwyn County, testing 72-2 per cent, of flour, which is regarded as a good amount.

The variety Victor gave very interesting results. One sample from Kirwee (P 323) gave the excellent milling-yield of 76 per cent, flour, and three others very good yields —namely, those from Horrelville (75-5 per cent.), Domett (74-4 per cent.), and Irwell (73-5 per cent.). These again (see Solid-straw Tuscan) are all from North Canterbury. A sample from Glenavy, Waimate, gave the fair yield of 71-7 per cent. The average of the five samples is therefore very high, and Victor must be considered, so far as the 1922 figures show, as a variety usually yielding a high percentage of flour. More, however, will be said later regarding the strength of this variety.

There remain six samples which are grouped under the heading “Miscellaneous.’' Two samples of Dreadnought, both from Waitaki, yielded very good percentages of flour'—75 and 73-1.. This is an interesting variety, and it is to be regretted that more samples of it were not received for milling tests. A sample of Huron gave the very good yield of 74-9 per cent, of flour. Marquis was a good wheat with 72-4 per cent. There was then a drop to Thew with 71-1 per cent. These results are interesting, and further reference will be made to them later.

SUMMARY AND CONCLUSION.

Summarizing the results, it may be said that in 1922 the Lakes district produced wheats with good milling-qualities, while each of the three samples received from the Upper Taieri was good. The south and middle Canterbury wheats ■ were on the whole very satisfactory in. flour-percentage, out of the total number of samples tested two only not being , classified as good. Those from north Canterbury reached an equally , good standard, more than half of them giving good and very good percentages of flour.

- Interesting results were obtained from several varieties not grown to any great extent in New Zealand, and this would suggest that experiments might be tried with these. Provided that their yields per acre were satisfactory, it might be found that they would be specially adapted to certain districts, yielding more satisfactory amounts of flour than some varieties now grown.

On the average the flour-producing quality of New Zealand wheats is shown to be very fair. But, naturally, it will be in the interests of the grower, the miller, the baker, and. the consumer if that proportion of the wheats which is yielding not such a good average of flour can be eliminated and in its place the better varieties grown. This should be possible by the. adaptation of special wheats to special localities, though what varieties are better adapted than others to this purpose can be detei mined only by actual experiment. It would appear that the average amount of flour produced by those wheats milling only about 71 per cent, could be increased by some 2 to 3 per cent, or even more. It is needless to point out how much such an increase would affect and improve the all-round value of the Dominion’s wheat crop; especially is this so when one ' considers that an improvement' of 2 to 3 per cent, on the gross yield of flour may actually represent an increase of 10 to 15 per cent, in net profits.

REFERENCES IN TEXT.

(1.) A. E. Humphries and R. H. Biffen : The Improvement of English Wheat. Jour, of Ag. Science. Cambridge, 1907, p. 1.

(2.) T. B. Wood : The Story of a Loaf of Bread. Cambridge University Press 1913. ' .. • ’

(3.) W. I.. Stockham : Some Factors related to Quality of Wheat and Strength of Flour. Bulletin 139, N. Dakota Exp. Station, 1920.

(4.) J. Zinn : Correlation between various Characters of Wheat and Flour. Jour, of Ag. Research, 1922, p. 529. (5.) H. F. Roberts : The Relation of Protein Content to Variety Types in American Wheats. Jour, of Ag. Science, 1920, P- 121.

(6.) F. T. Shutt ; Influence, of Environment on Composition of Wheat. Jour, of Society of Chemical Industry, I9°9> P- 339.

(7.) Agricultural Gazette of New South Wales, 1918, 1919, 1920, 1921. (8.) International Review of the Science and Practice of Agriculture, Rome, 1922, p. i33i- .

Laboratory Number. Variety. ■ Locality and County. Bran. Pollard. Flour. Remarks on Yield of Flour. . P 307 Pearl Weedon’s, Paparua. . Per Cent. 9’3 Per Cent. I5-5 1 Per Cent. 75'2 Very good.. P 382 Frankton, Lake 14-4 n-3 74'3 O 81 I Lincoln, Springs 12-3 13-9 73-8 P 306 Leeston, Ellesmere . . n-5 16-1 72-4 Good. O 812 Velvet (selected) Lincoln, Springs . . . 9-o 15-8 Very good. P 294 Dumbarton, Tuapeka 9-0 15’8 75’2 Very good. p 294 Velvet Velvet . Dumbarton, Tuapeka 12-6 13’3 74-i p 262 Windsor Downs, Wai-II-I 15-8 73’i p 292 mate Nenthorn (Moonlight), 12’9 14-2 72-9 Good. . p 291 Upper Taieri Middlemarch, Upper 12-2 15-2 72-6 P 290 Taieri Ditto . . • . . 12-9 15-3 71-8 p 327 Wrev's Bush, Wallace . .. 12-3 Wrev’s Bush, Wallace 16-6 I2‘3 71-6 16-6 71-6 p 468 Winton, Southland . . 15-6 T.2’9 7 I- 5 0 814 Lincoln, Springs 1'3-5 15-7 70-8' P 310 Hunters Killinchy, Ellesmere 14-2 14-0 71-8 P 29 .5 College Hunters Dumbarton, Tuapeka IS’ 0 1.3-4 73’6 Very good. p 265 •. Airedale, Waitaki . . Airedale, Waitaki. . . 12’8 12-8 14-2 14-2 73’0 73’0 Good. ■ Good. P 313 Lincoln, Springs 14-8 13-5 7.1-7 P 308 Doyleston, Ellesmere ■ 13-4 i5’i 71-5 P 383 Tuscan . ■ Malaghan’s, Lake . . 13-0 14-4 72-6 P 379 Lake . . ii-4 16-8 71-8 P381 White Tuscan 14-0 13-8 72-2 P467 *, Winton, Southland . . Winton, Southland . . 13-7 13-7 ia-8 ia-8 7-1-5 7i-5 P 315 Solid-straw TusAnnat, Malvern 9’5 16-3 74-2 Very good. P 314 can Ditto Domett, Cheviot. Ii-O 1.5-2 73'8 P316 ,, . • • Hawkins, Selwyn 12-2 14-5 73’3 P 325 - ,. . . • Athol, Wallace Athol, Wallace 10-9 10-9 17-2 17-2 71-9 7i-9 Good. Good. P 3i9 Purple - straw Greendale, Selwyn . . 14-4 I3-7 72-2 .. P 323 Tuscan Victor Kirwee, Malvern 1-5 12-5 76-0 Excellent. P321 Horrelville, Eyre »» 12-7 Horrelville, Eyre n-8 . 12’7 75-5 n-8 Very good. 75’5 Very good. P 322 Domett, Cheviot 10-9 14'7 74'4 P 324 ,, • • Irwell, Ellesmere . . 1'3-4 I3-I I 73-5 P 263 ] >} • • Glenavy, Waimate . . 1 Glenavy, Waimate . . ' I2-I I2-I 16-2 16-2 71-7 71-7 Good. Good. P 260 | Dreadnought Miscellaneous Kurow, Waitaki n-5 13-5 75 Very good. P 259 Kia Ora, Waitaki 10-5 16-4 73-i P43I Huron . . Dumbarton, Tuapeka . 13-7 11-4 74 : 9 P 429 Marquis ' 12-4 15’2 72-4 Good. P 432 1 Thew . . 14-6 14-3 .71-1 O 81.5 I Burbank’s Super Flaxton, Rangiora .. 14-0 16-0 70-0

TABLE I. —MILLING TESTS OF NEW ZEALAND WHEATS (SELECTED RESULTS).

Class. Variety. Number of Samples. ' Average Percentage of Flour. Pearl Pearl . . 5 73’3 Velvet IO 7 2 '4 Hunters . . Velvet . . : . . IO 72-4 College Hunters . . . . 12 71-2 Tuscan Victor .. . . 6 73'7 • • -•> Solid-straw Tuscan Solid-straw Tuscan 7 7 72-0 72-0

Though the number of samples received in some cases was too small to produce reliable averages, the following figures are given for the totals of some of the varieties tested in 1922 :—