The following account of the preservative quality of pyro-ligneous[33]
acid, exhibited in a memoir by Dr. Wilkinson to the Bath Society, is
highly important:--
[33] Philosophical Magazine, 1821, No. 273, p. 12.
“Mr. Sockett having directed his attention to the smoking of hams with
wood smoke, either in a building erected for that purpose, or in a
chimney where wood alone is burned, in addition to its considerable
increase of flavour, he considered it more effectually preserved from
putrefaction by being, what is commonly called, smoke-dried. Mr. Sockett
having ascertained by experiments, that meat thus cured required less
salt, he was induced to suppose some antiseptic quality in the same,
and not attributable to the mere application of heat. A neighbouring
manufactory of pyro-ligneous acid afforded him an opportunity of trying
a variety of experiments, which convinced him of the correctness of the
supposition of the antiseptic quality of wood smoke, as the same effects
as to flavour and preservation were produced in a superior degree
without the aid of any increase of temperature, which, by drying,
diminishes the nutritious quality of meat thus exposed.”
“Mr. Sockett ascertained, that if a ham had the reduced quantity of salt
usually employed for smoke-dried hams, and was then exposed to smoke,
putrefaction soon took place when pyro-ligneous acid was not used; even
one half this reduced portion of salt is sufficient when it is used,
being applied cold, and the ham is thus effectually cured without any
loss of weight, and retaining more animal juices.”
“The mode adopted was by adding about two table-spoonfuls of
pyro-ligneous acid to the pickle for a ham of 10 or 12 lbs.; and when
taken out of the pickle, previous to being hung up, painted over with
the acid, by means of a brush. In many instances, Mr. Sockett has
succeeded by brushing the ham over with the acid, without adding any to
the pickle. The same mode answers equally well with tongues, requiring a
little more acid, on account of the thickness and hardness of the
integuments.”
“Upon dried salmon it answers admirably; brushing it over once or twice
had a better effect than two months smoking in the usual way, and
without the same loss from rancidity. From the result of a few
experiments on herrings, he is persuaded that this mode of curing might
be most advantageously introduced in our fisheries, so that herrings
might be cured here superior to those imported from Holland.”
“These experiments so satisfactorily demonstrating the antiseptic
qualities of this acid, where only small portions of salt were employed,
Mr. Sockett was then induced to try the results of the application of
this acid when no salt was employed: he placed some beef steaks upon a
plate, and covered the bottom with the acid, the steaks being daily
turned; and at the time of recording the experiment, he noticed that
they kept above six weeks without the least tendency to putrefaction:
this experiment was made in the middle of July 1815.”
“Not only Mr. Sockett, but many families in Swansea, and its vicinity,
practise, with the greatest success, this mode of curing hams, tongues,
beef, fish, &c.”
“This acid is very easily and cheaply prepared: the first distilled
product of the wood, in that state denominated black acid, answers the
best when separated from its tar and naphtha. More than 70 gallons of
acid, sufficiently strong, are procured from a ton of wood; a gallon is
quite sufficient for 2¹⁄₂ cwt. of pork, beef, and most animal
substances, with the addition of a comparatively small portion of salt,
not only affording a considerable saving in this article, but also
materially contributing to the increase of flavour and nutritive
quality. Hams or beef cured this way require no previous soaking in
water to being boiled, and when boiled swell in size and are extremely
succulent.”
“Herrings Mr. Sockett cures with very little salt. Being well dried, as
early after being caught as can be effected, they are then dipped into a
vat of the acid, and when dry, the same process repeated a few times,
suspending them like the manufacture of candles. Mr. Sockett entertains
no doubt, from the result of his experiments with herrings, that the
same process would answer for other kinds of fish, as salmon, cod, &c.;
and hence, when cooked, may be salted according to each individual’s
taste.”
“I presume this acid would be found very useful on board any vessel
fitted out for long voyages; it appears from calculations on a small
scale, that one hogshead of this acid would suffice to cure six tons of
fish, in such a manner as to retain their nutritious quality; and they
could be cured on board when opportunities occurred of procuring them,
independent of its being an excellent substitute for common vinegar in
many culinary purposes on board.”
“Mr. Sockett recommends that fish, as soon as practicable after taken,
should be a little rubbed with salt, and laid upon a sloping board to
drain, and when dry, to be dipped in the acid as before stated.”
“One great advantage attending this mode of curing hams or beef is, that
when hung up they are never attacked by the flies.”