VEGETABLE CASEIN AND VEGETABLE JUICES.
AS most of my readers doubtless know, peas, beans, lentils and other
seeds of leguminous plants are more nutritious, theoretically, than the
seeds of grasses, such as wheat, barley, oats, maize, &c. I was glad
to see at the Health Exhibition a fine series of the South Kensington
cases, displaying in the simplest and most demonstrative manner the
proximate analyses of the chief materials of animal and vegetable food.
I refer to them now because they did not receive the attention they
deserve. On the opening day there was, out of all the crowd, only one
other besides myself bestowing any attention upon them. These cases
show 1 lb. of wheat, oats, potatoes, peas, &c. &c., on trays; by the
side of these are bottles, containing the quantity of water in the 1
lb., and other trays, containing the other constituents of the same
quantity; the starch, gluten, casein, the mineral matter, &c., thus
displaying at a glance the nutritious value of each so far as chemical
analysis can display it. Those Irishmen and others who think I have
been too hard upon the potato, will do well to take its nutritive
measure thus, and compare it with that of other vegetable foods. I
should add that these cases form a part of the permanent collection of
the South Kensington Museum, and therefore may be studied at any time.
All the leguminous seeds, the ground-nuts, &c., have their nitrogenous
constituents displayed under the name of ‘casein.’ The use of this term
is rather confusing. In many modern books it does not appear at all in
connection with the vegetable kingdom, but is replaced by ‘legumin.’
Liebig regarded this nitrogenous constituent of the leguminous seeds,
almonds, &c., as identical with the casein of milk, and it was a
pupil and friend of Liebig’s—the late Prince Consort—who devised and
originally supervised this graphic method of displaying the chemistry
of food.[16]
I will not here discuss the vexed question of whether the analyses
of Liebig, identifying legumin with casein, or rather those of Dumas
and Cahours, who state that the vegetable casein is not of the same
composition as animal casein, are correct.
The following figures display my justification for thus lightly
treating the discussion:
+--------------------+--------+---------+---------+---------+
| -- | Casein | Legumin | Legumin | Legumin |
+--------------------+--------+---------+---------+---------+
| Carbon | 53·7 | 50·50 | 55·05 | 56·24 |
| Hydrogen | 7·2 | 6·78 | 7·59 | 7·97 |
| Nitrogen | 16·6 | 18·17 | 15·89 | 15·83 |
| Oxygen and Sulphur | 22·5 | 24·55 | 21·47 | 19·96 |
+--------------------+--------+---------+---------+---------+
The first column shows the results of Dumas for animal casein; the
second, those of Dumas and Cahours for legumin; the third, those of
Jones for the same; and the fourth, those of Rochleder; all as quoted
by Lehmann. Here it will be seen that the differences upon which
Dumas and Cahours base their supposed refutation of the identity of
the animal with the vegetable principle are much smaller than the
differences between the results of different analyses of the latter.
These differences I suspect are all due to the difficulty of isolating
the substances in question, especially of the vegetable substance,
which is so intimately mixed with the starch, &c., in its natural
condition that complete separation is of questionable possibility. The
difficulty (or impossibility) of driving off all the adhering water,
without removing the combined elements of water, is a further source of
discrepancy.
This will be understood by the following description of the method of
separation as given by Miller (‘Elements of Chemistry,’ vol. iii.).
‘Legumin is usually extracted from peas or from almonds, by digesting
the pulp of the crushed seeds in warm water for two or three hours. The
undissolved portion is strained off by means of linen, and the turbid
liquid allowed to deposit the starch which it holds in suspension; it
is then filtered and mixed with dilute acetic acid. A white flocculent
precipitate is thus formed, which must be collected on a filter and
washed.’
This is but a mechanical process, and its liability to variation
in result may be learned by anybody who will repeat it, or who has
separated the gluten of flour by similar treatment.
Practically regarded in relation to our present subject, casein and
legumin may be considered as the same. Their nutritive values are
equal, and exceptionally high, supposing they can be digested and
assimilated. One is the most difficult of digestion of the nitrogenous
constituents of vegetable food, and the other enjoys the same
distinction among those of animal food. Both primarily exist in a
soluble form; both are rendered solid and insoluble in water by the
action of acids; _both are precipitated as a curd by rennet_, and both
are rendered soluble after precipitation, or are retained in their
original soluble form by the action of alkalies. They nearly resemble
_in flavour_, and John Chinaman makes actual cheese from peas and beans.
Pease-pudding hot, pease-pudding cold,
Pease-pudding in the pot, nine days old.
I leave to Mr. Clodd the historical problem of determining whether this
notable couplet is of Semitic, Aryan, Neolithic, or Paleolithic origin.
Regarded from my point of view, it expresses a culinary and chemical
principle of some importance, and indicates an ancient practice that is
worthy of revival.
I have lately made some experiments on the ensilage of human food,
whereby the cellular tissue of the vegetable may be gradually subjected
to that breaking up of fibre already described. One of the curious
achievements of chemical metamorphoses that is often quoted as a matter
for wonderment is the conversion of old rags into sugar by treating
them with acid. The wonderment of this is diminished, and its interest
increased, when we remember that the cellulose or woody fibre of which
the rags are composed has the same composition as starch, and thus
its conversion into sugar corresponds to the every-day proceedings
described in Chapter XI. All that I have read and seen in connection
with the recent ensilage experiments on cattle fodder indicate that
it is a process of slow vegetable cookery, a digesting or maceration
of fibrous vegetables in their own juices, which loosens the fibre,
renders it softer and more digestible, and not only does this, but, to
some extent, converts it into dextrin and sugar.
I hereby recommend those gentlemen who have ensilage-pits and are
sufficiently enterprising to try bold experiments, to water the fodder,
as it is being packed down, with dilute hydrochloric acid or acetic
acid, which, if I am not deluded by plausible theory, will materially
increase the sugar-forming action of the ensilage. The acid, if
not over-supplied, will find ammonia and other bases with which to
neutralise itself.
Such ensilage will correspond to that which occurs when we gather
Jersey or other superlatively fine pears in autumn as soon as they are
full grown. They are then hard, woody, and acid, quite unfit for food,
but by simply storing them for a month, or two, or three, they become
lusciously tender and sweet; the woody fibres are converted into sugar,
the acid neutralised, and all this by simply fulfilling the conditions
of ensilage, viz. close packing of the fibre, exclusion of air by the
thick rind of the fruit, _plus_ the other condition which I have just
suggested, viz. the diffusion of acid among the well-packed fibres of
the ensilage material.
In my experiments on the ensilage of human food I have encountered
the same difficulty as that which has troubled graziers in their
experiments, viz. that small-scale results do not fairly represent
those obtained with large quantities. There is besides this another
element of imperfection in my experiments respecting which I am bound
to be candid to my readers, viz. that the idea of thus extending the
principle was suggested in the course of writing this series, and,
therefore, a sufficient time has not yet elapsed to enable me (with
much other occupation) to do practical justice to the investigation.
I find that oatmeal-porridge is greatly improved by being made some
days before it is required, then stored in a closed jar, brought
forth and heated for use. The change effected is just that which
theoretically may be expected, viz. a softening of the fibrous
material, and a sweetening due to the formation of sugar. This
sweetening I observed many years ago in some gruel that was partly
eaten one night and left standing until next morning, when I thought
it tasted sweeter; but to be assured of this I had it warmed again two
nights afterwards, so that it might be tasted under the same conditions
of temperature, palate, &c., as at first. The sweetness was still more
distinct, but the experiment was carried no further.
I have lately learned that my ensilage notion is not absolutely new.
A friend who read my Cantor Lectures tells me that he has long been
accustomed to have his porridge made some days before eating it, then
having it warmed up when required. He finds the result more digestible
than newly-made porridge. The classical nine days’ old pease-pudding
is a similar anticipation, and I find, rather curiously, that nine
days is about the limit to which it may be practically kept in a cool
place before mildew—mouldiness—is sufficiently established to spoil
the pudding. I have not yet tried a barrel full of pease-pudding or
moistened pease-meal, closely covered and powerfully pressed down, but
hope to do so.
Besides these we have a notable example of ensilage in sour-kraut—a
foreign luxury that John Bull, with his usual blindness, denounces,
as a matter of course. ‘Horrid stuff!’ ‘beastly mess!’ and such-like
expressions I hear whenever I name it to certain persons. Who are
these persons? Simply English men and English women who have never
seen, never tasted, and know nothing whatever of what they denounce
so violently, in spite of the fact that it is a staple article of food
among millions of highly-intelligent people. Common sense (to say
nothing of that highest result of true scientific training, the faculty
of suspending judgment until the arrival of knowledge) should suggest
that some degree of investigation should precede the denunciation.
In the cases of the sour-kraut and the ripening pear there is acid at
work upon the fibre, which, as I have before stated, assists in the
conversion of this indigestible constituent into soluble and digestible
dextrin and sugar.
The demand for the solution of the vegetable casein or legumin, which
has such high nutritive value and is so abundant in peas, &c., is of
the opposite kind. Acids solidify and harden casein, alkalies soften
and dissolve it. Therefore the chemical agent suggested as a suitable
aid in the ensilage or slow cookery, or the boiling or rapid cookery,
of leguminous food is such an alkali as may be wholesome and compatible
with the demands for nutrition.
The analyses of peas, beans, lentils, &c., show a deficiency of
potash salts as compared with the quantity of nitrogenous nutriment
they contain; therefore I propose, as in the case of cheese food,
that we should add this potash in the convenient and safe form of
bicarbonate—not merely add it to the water in which the vegetables may
be boiled, and which water is thrown away (as in the common practice
of adding soda when boiling greens), but add the potash to the actual
pease-porridge, pease-pudding, lentil soup, &c., and treat it as a part
of the food as well as an adjunct to the cookery. This is especially
required when we use dried peas, dried beans of any kind, such as
haricots, dried lentils, &c.
I find that taking the ordinary yellow split-peas and boiling them
in a weak solution of bicarbonate of potash for two or three hours, a
partial solution of the casein is effected, producing pease-pudding, or
pease-porridge, or _purée_ (according to the quantity of water used),
which is softer and more gelid than that which is obtained by similarly
boiling without the potash. The undissolved portion evidently consists
of the fibrous tissue of the peas, the gelatinous or dissolved portion
being the starch, with more or less of casein. I say ‘more or less,’
because at present I have not been able to determine whether or not the
casein is _all_ rendered soluble.
The flavour of the clear pea-soup which I obtained by filtering through
flannel shows that some of the casein is dissolved; this is further
demonstrated by adding an acid to the clear solution, which at once
precipitates the dissolved casein. The filtered pea-soup sets to a
stiff jelly on cooling, and promises to be a special food of some
value, but for the reasons above stated, I am not yet able to speak
positively as to its quantitative value. The experience of any one
person is not sufficient for this, the question being, not whether
it contains nutritive material—this is unquestionable—but whether it
is easily digested and assimilated. As we all know, a food of this
kind may ‘agree’ with some persons and not with others—_i.e._ it may
be digested and assimilated with ease or with difficulty according
to personal idiosyncrasies. The cheesy character of the abundant
precipitate which I obtain by acidulating this solution is very
interesting and instructive, regarded from a chemical point of view.
The solubility of the casein is increased by soaking the peas for some
hours, or, better still, a few days, in the solution of bicarbonate of
potash.
Another question is opened by these experiments, viz. what is the
character and the value of the fibrous solid matter remaining behind
after filtering out the clear pea-soup? Has the alkali acted in an
opposite manner to the acid in the ripening pear? Is it merely a
fibrous refuse only fit for pig-food, or is it deserving of further
attention in the kitchen? Should it be treated with dilute acid—say
a little vinegar—to break up the fibre, and thereby be made into
good porridge? Other questions crop up here as they have been
cropping continually since I committed myself to the writing of these
papers, and so abundantly that if I could afford to set up a special
laboratory, and endow it with a staff of assistants, there would be
some years’ work for myself and staff before I could answer them
exhaustively, and, doubtless, the answers would suggest new questions,
and so on _ad infinitum_. I state this in apology for the merely
suggestive crudity of many of the ideas that I have thrown out.
Before leaving the subject of peas, I must here repeat a practical
suggestion that I published in the ‘Birmingham Journal,’ about twenty
years ago, viz. that the water in which green peas are boiled should
not be thrown away. It contains much of the saline constituents of the
peas, some soluble casein, and has a fine flavour, the very essence
of the peas. If to this, as it comes from the saucepan, be added a
little stock, or some Liebig’s ‘Extract,’ a delicious soup is at once
produced, requiring nothing more than ordinary seasoning. With care,
it may form a clear soup such as just now is in fashion among the
fastidious, but prepared however roughly, it is a very economical,
wholesome, and appetising soup, and costs a minimum of trouble.
I must here add a few words in advocacy of the further adoption in
this country of the French practice of using as _potage_ the water in
which vegetables generally (excepting potatoes) have been boiled.
When we boil cabbages, turnips, carrots, &c., we dissolve out of them
a very large proportion of their saline constituents; salts which are
absolutely necessary for the maintenance of health; salts without which
we become victims of gout, rheumatism, lumbago, neuralgia, gravel, and
all the ills that human flesh with a lithic acid diathesis is heir
to; _i.e._ about the most painful series of all its inheritances. The
potash of these salts existing therein in combination with organic
acids is separated from these acids by organic combustion, and is
then and there presented to the baneful lithic acid of the blood and
tissues, the stony torture-particles of which it converts into soluble
lithate of potash, and thus enables them to be carried out of the
system.
I know not which of the Fathers of the Church invented fast-day and
_soupe maigre_, but could almost suppose that he was a scientific monk,
a profound alchemist, like Basil Valentine, who, in his seekings for
the _aurum potabile_, the elixir of life, had learned the beneficent
action of organic potash salts on the blood, and therefore used the
authority of the Church to enforce their frequent use among the
faithful.
The above remarks when published in ‘Knowledge’ invoked much
correspondence, including many inquiries for further information
concerning the salts that should be contained in our food, and in what
other form they might be obtained.
I therefore add the following, especially as I can speak from practical
experience of the miseries that may be escaped by understanding and
applying it. I inherit what is called a ‘lithic acid diathesis.’ My
father and his brothers were martyrs to rheumatic gout, and died early
in consequence. I had a premonitory attack of gout at the age of
twenty-five, and other warning symptoms at other times, but have kept
the enemy at bay during forty years by simply understanding that this
lithic acid (stony acid) combines with potash, forming thus a soluble
salt, which is safely excreted. Otherwise it is deposited here or
there, producing gout, rheumatism, stone, gravel, and other dreadfully
painful diseases, which are practically incurable when the deposit is
fairly established. By effecting the above-named combination in the
blood the deposition is _prevented_.
The potash required for the purpose exists in several conditions.
First, in its uncombined state as caustic potash. This is poison, for
the simple reason that it combines so vigorously with organic matter
that it would decompose the digestive organs themselves if presented to
them. The lower carbonate is less caustic, the bicarbonate nearly, but
not quite, neutral. Even this, however, should not be taken as _food_,
because it is capable of combining with the acid constituents of the
gastric juice.
The proper compounds to be used are those which correspond to the
salts existing in the juices of vegetables and flesh, viz. compounds
of potash with _organic_ acids, such as tartaric acid, which forms the
potash salt of the grape; such as citric acid, with which potash is
combined in lemons and oranges; malic acid, with which it is combined
in apples and many other fruits; the natural acids of vegetables
generally; lactic acid in milk, &c.
All these acids, and many others of similar origin, are composed of
carbon, oxygen, and hydrogen, held together with such feeble affinity
that they are easily dissociated or decomposed by heat. This may be
shown by heating some cream of tartar or tartaric acid on a strip of
metal or glass. It will become carbonised to a cinder, like other
organic matter. If the heat is raised sufficiently this cinder will all
burn away to carbonic acid and water in the case of the pure acid, or
will leave carbonate of potash if cream of tartar or other potash salt
is thus burned.
Unless I am mistaken, this represents violently what occurs gradually
and mildly in the human body, which is in a continuous state of slow
combustion so long as it is alive. The organic acids of the potash
salts suffer slow combustion, give off their excess of carbonic acid
and water to be breathed out, evaporated, and ejected, leaving behind
their potash, which combines with the otherwise stony lithic acid just
when and where it comes into separate existence by the organic actions
which effect the above-described slow combustion.
If we take potash in combination with a mineral acid, such as the
sulphuric, nitric, or hydrochloric, no such decomposition is possible;
the bonds uniting the elements of the mineral acid are too strong to
be sundered by the mild chemistry of the living body, and the mineral
acid, if separated from its potash base, would be most mischievous, as
it precipitates the lithic acid in its worst form.
For this reason, all free mineral acids are poisons to those who have
a lithic acid diathesis; they may even create it where it did not
previously exist. Hence the iniquity of cheapening the manufacture of
lemonade, ginger-beer, &c., by using dilute sulphuric or hydrochloric
acid as a substitute for citric or tartaric acid. I shall presently
come to the cookery of wines, and have something to say about the
mineral acids used in producing the choicer qualities of some very
‘dry,’ high-priced samples which, according to my view of the subject,
have caused the operations of lithotomy and lithotrity to be included
among the luxuries of the rich.
It should be understood that when I recommended the use of bicarbonate
of potash for the solution of casein, all these principles were kept
in view, including the objection to the bicarbonate itself. In the
case of the cheese, the quantity recommended was based on an estimate
of the quantity of lactic acid existing in the cheese and capable of
leaving the casein to go over to the potash. In the case of the peas
the quantity is difficult to estimate, owing to its variability. The
more correct determination of such quantities is among the objects of
further research to which I have before alluded.
Speaking generally it is not to the laboratory of the chemist that we
should go for our potash salts, but to the laboratory of nature, and
more especially to that of the vegetable kingdom. They exist in the
green parts of all vegetables. This is illustrated by the manufacture
of commercial potash from the ashes of the twigs and leaves of timber
trees. The more succulent the vegetable the greater the quantity of
potash it contains, though there are some minor exceptions to this. As
I have already stated, we extract and waste a considerable proportion
of these salts when we boil vegetables and throw away the _potage_,
which our wiser and more thrifty neighbours add to their every-day
_menu_. When we eat raw vegetables, as in salads, we obtain all their
potash.
Fruits generally contain important quantities of potash salts, and
it is upon these especially that the possible victims of lithic acid
should rely. Lemons and grapes contain them most abundantly. Those who
cannot afford to buy these as articles of daily food may use cream of
tartar, which, when genuine, is the natural salt of the grape, thrown
down in the manner I shall describe when on the subject of the cookery
of wines.
At the risk of being accused of presumption, I must here protest, as a
chemist, against one of ‘the fallacies of the faculty,’ or of certain
members of the faculty, viz. that of indiscriminately prohibiting to
gouty and rheumatic patients the use of acids or anything having an
acid taste.
This has probably arisen from experience of the fact that _mineral_
acids do serious mischief, and that alkaline carbonate of potash
affords relief. The difference between the organic acids, which are
decomposed in the manner I have described, and the fixed composition of
the mineral acids, does not appear to have been sufficiently studied by
those who prohibit fruit and vegetables on account of their acidity.
It must never be forgotten that nearly all the organic compounds of
potash, as they exist in vegetables and fruit, are acid. It may be
desirable, in some cases, to add a little bicarbonate of potash to
neutralise this excess of acid and increase the potash supply. I have
found it advantageous to throw a half-saltspoonful of this into a
tumbler of water containing the juice of a lemon, and have even added
it to stewed or baked rhubarb and gooseberries. In these it froths like
whipped cream, and diminishes the demand for sugar, an excess of which
appears to be mischievous to those who require much potash.
I must conclude this sermon on the potash text by adding that it is
quite possible to take an excess of this solvent. Such excess is
depressing; its action is what is called ‘lowering.’ I will not venture
upon an explanation of the _rationale_ of this lowering, or discuss
the question of whether or not the blood is made watery, as sometimes
stated.
Intimately connected with this part of my subject is another vegetable
principle that I have not yet named. This is vegetable jelly, or
_pectin_, the jelly of fruits, of turnips, carrots, parsnips, &c.
Fremy has named it _pectose_. Like the saline juices of meat it is
very little changed by cookery. An acid may be separated from it which
has been named ‘pectic acid,’ the properties and artificial compounds
of which appear to me to suggest the theory that the natural jelly of
fruits largely consists of compounds of this acid with potash or soda
or lime. We all know the appearance and flavour of currant jelly, apple
jelly, &c., which are composed of natural vegetable jelly plus sugar.
The separation of these jellies is an operation of cookery, and one
that deserves more attention than it receives. I shall never forget
the _rahat lakoum_, prepared for the Sultana, which I once had the
privilege of eating in the kitchen of the Seraglio of Stamboul, where
it was presented to me by his Excellency the Grand Confectioner as
a sample of his masterpiece. Its basis was the pure pectose of many
fruits, the inspissated juices of grapes, peaches, pine-apples, and I
know not what others. The sherbet was similar, but liquid. Well may
they obey the Prophet and abstain from the grosser concoctions that
we call wine when such ambrosial nectar as this is supplied in its
place! It is to Imperial Tokay as tokay is to table-beer! I tasted many
other choice confections there, and when I find myself defending the
Turk against his many enemies, my conscience sometimes asks whether my
politics have been influenced by the remembrance of that visit.
The ‘lumps of delight’ sold by our confectioners are imitations made of
flavoured gelatin. Similar substitutes are sold in Constantinople. The
same as regards the sherbet.
I conclude this part of my subject by re-echoing Mr. Gladstone’s
advocacy of the extension of fruit culture. We shamefully neglect the
best of all food, in eating and drinking so little fruit. As regards
cooked fruit, I say jam for the million, jelly for the luxurious, and
juice for all. With these in abundance, the abolition of alcoholic
drinks will follow as a necessary result of natural nausea.
I may add that besides the letters asking for the further information
here given, I have since received several others from readers who have
adopted the diet above prescribed with good practical results.
I have further learned that vegetarians are remarkably free from the
lithic acid troubles above named, and that many who were sufferers
before they became vegetarians have subsequently escaped.
The testimony of a large number is demanded in such subjects, as
individual examples may depend upon individual peculiarities of
constitution.
FOOTNOTE:
[16] Shortly after the close of the Great Exhibition of 1851, when the
South Kensington Museum was only in embryo, I had occasion to call
on Dr. Lyon Playfair at the ‘boilers,’ and there found the Prince
hard at work giving instructions for the arrangement and labelling of
these analysed food products and the similarly displayed materials of
industry, such as whalebone, ivory, &c. I then, by inquiry, learned how
much time and labour he was devoting, not only to the general business
of the collection, but also to its minor details.