THE ANALYEIT. 53

DO CEREALS CONTAIN SUGAR." BY PROF. DR. ALEX. V. ASB~TH.

IN my paper on the determination of starch (see ANALYST, July, 1887) I came to the conclusion that cereals do not contain any sugar. Baryta water does not preci- pitate sugar in presence of alcohol, and still my full analyses of various cereals came veryclose up to 100 per cent., leaving, therefore, no room for any sugar. As, however, Windish pretends that, by following the details of my process, the sugar cannot be estimated, and many chemists of repute have found sugar, I once more investigated the matter so as to prove myself in the right.

TABLE, STIOWING THE AMOUNT OF SUGAR FOUND IN NON-GERMINATED BARLEY AND WHEAT BY SEVERAL AUTHORITIES ( KUHNEMANN).

('I 0 " means not found ; '' -" means not tried for.) BARLEY. W II EA T.

Sugar. Dextrin. Sugar. Dextrin. Per cent. Per cent. Pel. cent. l'er cent.

__ - - Thomson (1817) . . * . 4

Groust (181s) . . . . 5 4 Peligot . . . . . . 0 Boussingault . . . . _- 7.2

Polson . . . . . . -- 4.8 -- 5 3 - -

- -- - -

Saussure . . . . . . - - 2.4 3 4

} (Ism) . . 0 Mulder Oudemans

- -- - Mitscherlich . . . . 0 Her ms taed t . . . . 4.7 4.5 Einhof (1838) . . . . 5.3 4.6 W. Stein (1860) . . * . 0 6.5 Pillitz (1872) . . . . 2-71 1.96 1.60 1.76

According to Oudemans, analysts have now and then found sugar, because they extracted the flour with water, which caused the dextrin, and probably some of the starch, to invert. If flour is extracted with absolute alcohol, and the solution evaporated to drynessaresidue is obtained which, after inversion with strong acetic acid, reduces the copper solution, and yields about -2 per cent. of sugar ; but even these small traces are not really pregent as such in the original flour. Most likely they arederived from a little dextrin,

* Uherp, Zeit., 2 and 4, 1888,

-- c

- - - -

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54 THE ANALYST.

as this substance is not quite insoluble in alcohol, and flour probably contains small quan- tities of copper-reducing substances which need not necessarily be sugar.

Krocker extracts the flour with limewater and filters. The filtrate is freed from albuminoids and excess of lime by a current of carbonic acid. Sugar could not be detected in the filtrate.

Schlosing estimates sugar as follows :-lo to 19 grammes of finely ground sub- stance are repeatedly rubbed in a mortar with small quantities of water, and finally ex- hausted in a displacement apparatus. The filtrate is divided into three equal parts. Sugar is estimated by Fehling’s solution in o m half of one of these parts. The other portion is used for determining the dextrin.

H e evaporates the watery solution and then extracts with rectified spirits of wine. The alcohol is distillsd off and the residue dissolved in a definite volume of water. If much colouring matter is present some animal charcopl must be used. The filtrate is divided into two equal parts and the glucose estimated, best by the well-known mercury solution. The other part is heated with a few drops of sulphuric acid for two hours in the water-bath, and then treated like the first. Any increase in sugar is calculated to cane-sugar.

J. Bell gives the following method :-I0 grammes of finely powdered material are extracted with alcohol of 70 per cent. The alcoholic solution is evaporated, and the residue inverted with 5 C.C. of normal sulphuric acid. The sugar is then estimated by one of the well-known processes. To practically ascertain whether these processes give reliable results, and to prove my case, I have made the following experiments :--

1. 10 grms. of maize-flour were gelatinised with 50 C.C. of water, and, whilst still warm, mixed with 200 C.C. of 80 per cent. alcohol. After cooling, the liquid was filtered and evaporated to dryness. I took up the residue with a little water and tested a little of it with Fehling. Notwithstanding the fluid gave a copious precipitate with baryta water and proof spirit, I could scarcely get any reduction of the copper solution.

2 . About 16 grammes of maize-flour were extracted in the cold with 200 C.C. of 80 per cent. alcohol; the latter evaporated and the residue dissolved in water. This solution (which but sparingly reduced Fehling) was mixed with lime water and boiled. The excess of lime and other impurities were removed by carbonic acid and the filtrate evaporated to dryness. The residue was again treated with rectified spirits of wine, when an insoluble yellow powder remained undissolved. The filtrate had a brownish colour, and left, after evaporation, a brownish sticky mass, readily soluble in water. The substance is, no doubt, erythrodextrin. With iodine it gives a red colour, and it does not reduce Fehling until it has been boiled with hydrochloric acid,

3. Experiments with wheat and peas gave similar results. 4. 20 grms. of maize were extracted according to Schliisiag’s process. The solution

I now come to the following conclusions :-The cereak contain no sugar, neither Analysts who have apparently found it have made use of wrong

SchlGsiag’s process is wrong, because the erythrodextrin, and most likely some of

Koenig modifies this process.

This was impure dextrin.

This solution is precipitated by baryta water in presence of alcohol.

strongly reduced the alkaline copper solution.

glucose nor saccharose. processes.

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THE ANALYST. 55

the starch, yield a little glucose by mere treatment with water. Koenig’s modification is also wrong, as my experiments plainly prove cereals contain a gummy-like substance, soluble in alcohol, which yields glucose on boiling with acids. The process of J. Bell and Rasenach also gives inaccurate results, as dextrin is perceptibly soluble in rectified spirits of wine, and the subsequent boiling with acid will make this into glucose. Then there is also the dextrin-like substance which I have found in all cereals, and which also yields glucose on boiling with acids.

As dextrin and erythrodextrin slightly reduce copper solution on prolonged boiling, it is not to be wondered at I sometimes got, in my analpes, slight reductions which ought not to have taken place.

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