THE ANALYST. 123

T H E ANALYSIS O F MARMALADE. BY L. K. BOSELEY, Chemist to Messrs. T. Keiller and Son, Limited.

(Read at the Meeting, March 16, 1898.) HAVING had occasion lately to work out some methods for the analysis of marmalade and jams, I have thought that a description of these, together with several results showing the composition of marmalade, might be of interest to the members of this Society .

Very few analyses on this subject have been published up to the present time- indeed, a few made by Mr. Carter Bell, the Analyst for Chester, are the only ones I know of. These analyses, which have been published quite recently, are not at all in agreement with any which I have myself made; among them are four analyses of marmalade, of which I give particulars, together with a few quotations from the report : ‘( I n the manufacture of jam on a large scale glucose, or inverted sugar, is often used in the place of cane. But to attempt to estimate this adulteration would be hopeless, for in the manufacture of jam the acids of the fruit convert the cane- sugar, more or less, into glucose.”

The following analyses are then given : Water. Glucose. Cane-sugar. Ash.

1. Marmalade ,.. 20.5 21.05 37.77 0.305 2. ?, ... 21.8 15.62 34-38 0.31 3. 9 , ... 22.5 24.39 25.61 0.30 4. 2 9 ... 19.5 21-73 14-63 0.26

From the remarks quoted above, it would seem that Nr. Carter Bell is unable t o distinguish between the product of the action of sulphuric acid on starch, usually known as glucose, and the product of the action of a fruit acid on cane or beet sugar, usually known as invert sugar.

The sugar estimated in these analyses appears to me to be very much too low ; for if the last sample be taken, and the water, glucose, and cane-sugar added together, they amount to 55.86 per cent., a, figure which leaves 44.14 per cent. of dry fruit (the water being estimated), which is not possible. My own experience goes to prove that marmalades from various sources contain from 2& to 58 per cent. of dried fruit. The probability is that both the figures for water and for sugar are much too low, as I never met with a marmalade with so low a water as 19.5 per cent., and one which containsd 36.36 per cent. of total sugar, more than half of which was glucose, would be little thicker than water.

The following are the methods in use in my laboratory : Water.-This is estimated by taking a flat-bottomed porcelain basin containing

a glass rod, and weighing into i t about 7 to 8 gramines of the well-mixed marmalade. This is warmed, and dissolved in a few C.C. of 40 per cent. alcohol. From 12 to 15 grammes of silver-sand, which has been previously dried, if necessary, are now weighed into the basin, and the marmalade, sand, and alcohol thoroughly mixed with the glass rod. The basin is then heated on the water-bath for an hour, when 5 C.C. of absolute alcohol are added, and the basin again heated for one hour ; after this it is

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124 THE ANALYST.

transferred to the air-bath and dried at 95-100" C. for thirty-six hours, or until the weight is nearly constant.

Acidity.-This is estimated by weighing out 20 grammes of the marmalade, titrating with Fa soda, with phenolphthalein, or litmus-paper as indicator. The number of cubic centimetres used, multiplied by 0.035, gives the percentage calculated as citric acid.

SzLgurs.-The following methods are the best, supposing only cane and invert sugar to be present : Weigh out 65.12 grammes of the well-mixed marmalade in a sknall beaker, add successive quantities of coZd water-say, 50 c.c.-stir well, and decant into a 250 C.C. flask. Then transfer the peel to the flask, add basic lead acetate, until the solution is only slightly acid, make up to 250 c.c., and mix well. It is best not to add sufficient basic lead acetate to neutralize the solution, as one is apt to get lead in the filtrate, this being an objectionable feature, as a slight pre- cipitate is produced on adding acid to invert the solution which is apt to interfere with the polarimeter reading. The contents of the 250 C.C. flask are now filtered through a dry filter, and polarized at t" C. Fifty C.C. of the filtrate are placed in a flask, and 5 C.C. of pure, strong HC1 added, and the flask is heated on the water-bath till a thermometer suspended in the middle of the flask indicates 68" C. in ten minutes. Cool quickly to to, and again polarize. Then,

Cane-sugar = Direct - -inverted reading (this is the well-known Clerget formula). t o 144 -- 2

(Cane-sugar - direct reading) 100 Invert sugar = ____---I_. l_l

t" 44 -- 2

_ _ _ ~ ,

If glucose be present it will be indicated by the inverted reading being + instead of - , or, at all events, being very much smaller than usual. If this he the case, it will be necessary also to determine the cupric reducing power (in duplicate).

The details of the method are as follows : Weigh out 13.024 grammes of pure cane sugar, make up to 100 c.c., add 10 C.C. strong HC1, and invert as before. Cool, take 11 C.C. of this solution, neutralize, and make up to 100 C.C. This I call solution CL.

Dilute 20 C.C. of the filtrate used for direct polarization, and make up to 100 C.C. This I call solution b.

Take two beakers, and in each place 25 C.C. of Soxhlet's copper solution and 25 C.C. of Soxhlet's alkaline tartaric solution and 40 C.C. of water, add to one 10 C.C.

of solution a, and to the other 10 C.C. of solution b. Place both over flames and bring to the boil in four minutes, and boil for four minutes longer, filter off the reduced cuprous oxide, and weigh either as metallic copper or copper oxide. The cuprie reducing power of the marmalade, calculated as percentages of invert sugar, will be found by the following formula :

Cu (or CuO) from b 4 x Cu (or CuO) from a - - x 100.

The reason for making solution b four times as strong as solution u is that the

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THE ANALYST. 125

cupric reducing power of a marmalade is somewhere in the neighbourhood of 25 per cent.

Calculation of the Percentage of Glucose.-I need hardly point out that “glucose ” is not a chemical entity, but is a mixture of maltose, dextrin, dextrose, and probably intermediate compounds. The following table will give the composition of com- mercial glucoses. The first nine are taken from a paper by Weber and McPhearsou (“ Proceedings of the Eleventh Annual Convention of the Association of Official Agricultural Chemists,” p. 126) :

Total solids 78.9 80.1 80.8 50.3 85-6 87.4 80.0 81.1 86-6 78.9 [uID of solids 133.3 132.9 120.6 135.4 132.1 127.8 149-3 130.3 134.9 143.1 Cupric re-

g\ 56% 57-0 60.6 54.9 56.7 55.9 43.6 50.6 48.8 48.5 power of solids ... J

1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

Analysis No. 10 is by H. D. Richmond. The averge of these ten samples, which may be taken to fairly represent the mean coinposition of commercial glucose, is : Total solids, 81.9 ; [u],, of solids, 133.98 ; cupric reducing power of solids, 53.31.

From the paper referred to, I find that Weber and MacPhearson found thzt coin- mercial glucose, on the average, gave, in a solution containing 13,024 grammes per 100 c.c., a

Direct reading ... ... 85.45 sugar degrees. Inverted reading . . . ... 84.9 7 ,

The inverted reading is done by the method described above, which must be strictly adhered to, Herzfeld’s modification having given a much larger difference. It is seen that the change on inversion is practically nil, and therefore cane-sugar can be esti- mated in the presence of commercial glucose with very fair accuracy. The average [a],, of the solids of commercial glucose (133.98) is practically twice that of cane- sugar, and it may be assumed without much error that 1 per cent. of glucose solids will polarize 2 per cent. of cane-sugar. When cane-sugar is inverted, 100 park become 105.3 :

The cupric reducing power of inverted cane-sugar is therefore 105.3. The cupric reducing power of glucose solids, 53.13, is practically half this, and it may be assumed without much error that 1 per cent. of glucose will have a cupric reducing power equal to 0.5 per cent. of cane-sugar.

To calculate the percentage of cane-sugar, invert sugar, and glucose in a marma- lade, the following formula3 can be derived from the facts above mentioned :

C,,H2,01, + OII, = C,H,,O, + C,H,,O,.

Direct - inverted reading to 144 - - 2

Cane-sugar - direct reading __ __ + 4 cupric reducing power to 4+44-- 2

100’

Cane-sugar= ~ ~ . -- -~

Inverted sugar =

___

Glucose-= 2(cupric reducing power - inverted sugar).

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126 THE ANALYST.

I t must be borne in mind that the inverted sugar is given by all the above formuls as percentages of cane-sugar inverted, and not as percentages of actual invert sugar present, This is done for the sake of convenience, as by adding the cane and inverted sugar together the percentage of cane-sugar present will be given.

As a, test analysis, a marmalade, of which the composition was unknown to me, was made up containing :

Cane-sugar ... ... ... 40.0 per cent. Glucose .,. ... ... ... 20.0 ,,

Direct polarization ... ... ... +61.2 at 16.5 C. After inversion ... ... ... +18*2 ,, Cupric reducing power ... ... 16.48

From these results the composition was calculated as follows by the above formulz :

The figures found on analysis were as follows :

Cane-sugar ... 3;:; 1 40.0 total Inverted sugar ... Glucose - . . , 16.3 =glucose containing 81.9 per cent solids =

This result seems to indicate that cane-sugar, invert sugar, and commercial glucose can be estimated with sufficient accuracy in the presence of each other.

The following analyses give the composition of nearly all the best known brands of marmalade on the market, the results having been all obtained by the methods given above :

19.9 per cent.

1. Moisture ... 33.3

Inverted sugar., . 25.0

Undetermined ... 4.0

100.0

Sugar ... ... 37.2

Acidity ... . . 0.5

_-

6. Water ... ... 31-3

Inverted sugar.. . 23.9 Glucose ... 8.7

Undetermined ... 1.0

100.0

Sugar ... ... 34.7

Acidity ... ... 0.4

--

11. Water ... ... 30.7 Sugar . . . ... 19.7 Inverted sugar.. . 34-1 Glucose ... 13.3 Acidity ... ... 0.6 Undetermined ... 1.6

100.0 --

2. 33.1 42.1 21.0 0.3 3.5

100.0

7. 26.6 35.6 304 5.0 0.5 0.9

--

1oq.o 12.

31.1 32.9 17.9 14.3

0.4 3.4

100.0 --

3. 27.7 25.6 41.8 0.4 4.5

100.0

8. 30.0 33.9 11.1 22.9 0.4 1.7

100.0 13.

40.6 31.4 21-5 none

0.5 6 0

--

--

4. 30.6 32% 32.7 0.4 3.7

100.0

9. 25.3 22.8 38.2 11.6 0.4 1.7

100.0

28.6 44.7 21-9 none

0.6 4.2

--

--

14.

100.0 100.0

5. 31.5 33 -2 30.0 0.5 4.8

100.0

10. 31.7 32.8 30.4 none

0.5 4.6

100.0 15. 27.7 44.0 22.9 none

0.5 4.9

100.0 --

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THE ANALYST. 127

16. ... Water ... ... 28.6 ... Sugar ... ... ... 24.3

Inverted sugar ... ... ... 42.8 Acidity ... ... ... ... 0.6 Undetermined ... ... ... 3.7

100.0 The sample labelled No. 8 contained added geIatin or isinglass, and the sample

No. 16 was one of Messrs. Keiller’s marmalade, which had been kept for six years ; hence the abnormally high invert sugar. Nos. 11 and 12 were preserved with salicylic acid. The amount of invert sugar formed in a marmalade seems to be due to three causes : Firstly, the amount of acid present ; secondly, the length of time the cooking is continued; and, thirdly, the length of time it has been kept. The figures for undetermined matter vary somewhat, but as the error of separating and estimating a complicated mixture of sugars is thrown on this figure it is not surprising.

Sugar is naturally present in oranges, and a correction has been applied for the amount of fruit-sugar present in a marmalade ; it consists in subtracting 0.1 sugar degrees from the + reading, and 0.3 from the - reading-that is, supposing the normal quantity of marmalade to have been weighed out, namely, 65.12 grammes per 250 C.C.

In conclusion, I should like to express my thanks to Mr. H. Droop Richmond for help in confirming some of the results given in this paper.

DISCUSSION. The PRESIDENT having invited discussion, Mr. A. C. CHAPMAN inquired what assumption Mr. Boseley made in regard to the

composition of glucose in the method he had adopted. Ordinary commercial glucose (a mixture of dextrose, maltose, and occasionally dextrin) varied very much in com- position. The proportion of maltose, for instance, might be as little as 4 or 5 per cent., or as much as 25 per cent. Some samples contained no dextrin ak all, while others contained a fairly considerable quantity. I t would be necessary to assume a constant composition as a basis for purposes of analysis and calculation.

Mr. HEHNER observed that an important reference had been made in the paper to salicylic acid. Salicylic acid was often found in jam, and had given rise t’o a good deal of discussion. Mr. Boseley now stated that it was added to jam solely as a meansof adulteration, and in view of this he (Mr. Hehner) thought that its presence in jam might be somewhat more vigorously condemned than hitherto. The excuse that it prevented the preserve from going bad, and that it was not particularly harmful, might justify its being passed ; but when it was distinctly understood that it also afforded a means of adding water, the matter became very serious.

Mr. L. K. BOSELEY said, in reply to Mr. Chapman’s question, that the basis the calculations had been worked out upon was the cupric reducing power of the glucose, and also the [a], of the glucose solids. H e was sorrynot to have had time enough to make this clear when reading the paper, but Mr. Chapman would understand that the amount of dextrin, dextrose, etc., which the glucose contained did not enter into the calculation, that being based on the average cupric reducing power, etc., of glucose.

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