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65
Preservatives in Tinned, or Canned Foods.
Properly tinned, or canned, wholesome food needs no
added preservatives. Preservatives, when found, point (a)
to the food being partly decomposed previous to being
tinned, or canned, the preservatives being added to prevent
such tins or cans "blowing," i.e., becoming distended with
the accumulated gases of decomposition; or (b) to the fear of
the tinning, or canning, process not being efficient and trustworthy,
i.e., the tins or cans not being hermetically sealed.
In this connection, reference may be made to the practice of
tinned, or canned, foods being sent from abroad, and, on
arrival in England, being transferred to glass bottles or
jars, to meet a special demand amongst certain purchasers.
In such cases, the addition of preservatives becomes important,
so as to prevent any decomposition showing itself
in the contents which are transferred from the tins and cans
to the glass bottles or jars.
In any case it is desirable that, if preservatives be allowed,
their quantity should be limited, and their presence and
amounts declared on the labels on the tins or cans, e.g., not
more than one grain of salicylic acid per lb. weight of food,
etc. No formaldehyde or formalin preparations should be
used as preservatives, in view of their action on the digestive
system.
Metallic Impurities in Tinned, or Canned Foods.
In certain preserved foods, tin and lead are, at times,
found as impurities, arising from either the plating, or the
solder used in soldering the lids on to the tins or cans.
These metallic impurities are generally found in old tins or
cans of preserved food (e.g., old ship stores, but in amounts,
at times, sufficient to be injurious to health. Tinned, or
canned lobster, salmon, apricots and pineapples may be
mentioned in this connection—the acid juices dissolving out
proportions of any tin, or lead, with which they may come
into contact. A form of plating that is dangerous is the socalled
"terne" or semi-leadplating, whilst some tins or cans
are for quickness soldered with "spirits of lead" instead of
with resin. The need for using suitable plating and proper
solder, and of soldering only on the outside of tins or cans