It is now ascertained that in presence of a considerable proportion of water, wheat flour under the influence of heat undergoes a low degree at least of lactic fermentation, which will account for the souring of the ordinary samples when exposed to warm or humid climates. The same result will inevitably follow from their careless exposure in the holds of vessels. That this is particularly the case with many of the cargoes of wheat flour shipped to Great Britain, there is little reason to doubt. This may be partly owing to the great humidity of the English climate, as the deterioration is observed as well in the flour which is the produce of that country as in that which is received from abroad.
It is stated by Mr. Edlin, quoted in an article on Baking, in the Encyclopædia Britannica, that, "as a general rule, the London flour" is decidedly bad. The gluten generally wants the adhesiveness which characterizes the gluten of good wheat."
I have observed that, in the analyses of some of the samples of damaged flour, the proportions of what is set down under the head of glucose and dextrine are unusually large. This is perhaps due to the change produced in the starch by the action of diastase, and which may under certain circumstances be formed in wheat flour. It would seem, according to M. Guérin, that starch may thus be acted on even at slightly elevated temperatures. In one of his experiments, at a temperature no higher than 68 deg. Fahr., a quantity of starch, at the end of twenty-four hours, was converted into syrup, which yielded seventy-seven per cent. of saccharine matter.[28] It may be thought that I have overrated the importance of this subject, but it is believed that a careful examination of the facts will relieve me from this charge. I am now satisfied that, if the proportion of water in our exported breadstuffs could be reduced to about five or six per cent., one of the great causes of complaint in regard to them would be completely removed.
Kiln-drying of breadstuffs, and exclusion of air.—The injury which our breadstuffs sustain by the large proportion of water can of course be prevented only by careful drying before shipment, and by the employment of barrels rendered as impervious as possible to the influence of atmospheric moisture.
In my first report, I have spoken favorably of the process of drying by steam, according to the plan patented by Mr. J.R. Stafford. I still think this mode possesses great advantages over those previously followed, and which almost always injured the quality of the grain or flour: but from some trials which I have made during the past year, it is inferred that the exposure to the heat is perhaps usually not sufficiently prolonged to answer the purpose intended by the operation. I have often observed that samples of wheat flour, after being exposed to the heat of the salt water-bath oven (220 deg. Fahr.) for two or three hours, lost weight by a further continuance of the heat. An apparatus has been patented by Mr. J.H. Tower, of Clinton, N.Y., consisting of a cylinder of square apartments or tubes, into which the grain or flour is introduced, and subjected to heat while in rapid revolution. I examined samples which had been subjected to this operation, and ascertained that wheat flour, originally containing 14.80 per cent. of water, had the proportion reduced to 10.25 per cent., while in wheat the proportion of water was reduced from 14.75 to 8.55 per cent.
Now it is probable that by either of the above modes, and perhaps by many others, the various kinds of breadstuffs may be brought to that degree of dryness which, with ordinary care, shall protect them from subsequent injury; but in order to secure this advantage, the operation must be carefully performed, and experiments must be made to ascertain how long an exposure to heat is necessary to bring the sample to the proper degree of dryness, and to determine whether in any respect its quality is impaired. It has already been stated that absolute desiccation is not necessary, even were it attainable; but any process in order to be effective should reduce the proportion of water to about six, or at most seven per cent.
I have heretofore adverted to the great care employed in the drying of grain in various foreign countries, and to which the preservation of it for a great number of years is to be ascribed.
The operation is not conducted in the hurried manner which is here thought to be so essential, but is continued long enough to effect the intended object. Thorough ventilation, as well as the proper degree of drying, and which is equally important, is thus secured.
It is said that in Russia the sheaves of wheat, carried into the huts, are suspended upon poles and dried by the heat of the oven. The grain shrinks very much during this process, but it is supposed to be less liable to the attacks of insects, and preserves its nutritive qualities for many years. During the winter, it is sent to market.—("The Czar, his Court and People." By John S. Maxwell, p. 272.)
With all the necessary attention which may be paid to the proper drying of our breadstuffs intended for export, another point is of equal importance, viz., the shipment in vessels rendered as impervious as possible to the influence of atmospheric moisture. For however carefully and thoroughly the drying, especially of wheat flour or maize meal, may have been performed, it will be nearly useless if the shipment is afterwards made in the barrels commonly employed.[29] And it is very certain that the transport and shipment of grain in bulk, as usually conducted, are attended with great loss. This difficulty might be removed at a trifling expense by adopting the plan suggested in the preceding report, and to which I would again respectfully call the attention of those who are engaged in this branch of trade.