424 EVENING DISCOURSES 
reduce this bacterial contamination to a minimum, and while perfect 
asepsis is impossible, every possible precaution should be taken to keep the 
contamination at a low level. 
There should, indeed, be prominently displayed, in all places where 
foodstuffs are handled, Florence Nightingale’s maxim, ‘ Cleanliness is the 
only real disinfectant.’ 
Effect of Cold.—Fortunately, experiments show that the growth of these 
micro-organisms can be controlled by cold, the growth ceasing altogether at 
a temperature of — 7° C. Storage for very long periods is therefore possible. 
However, from slaughter-house to consumer meat cannot be kept con- 
tinuously at — 7° C., and the necessity for scrupulous cleanliness in the 
handling of foodstuffs is still essential: nothing else can make so great 
a contribution to success in their storage and transport. 
It thus appears that refrigeration forms the fundamental means whereby 
meat may be successfully stored and transported. ‘The freezing-point of 
meat is approximately —1° C., and if autolysis and the growth of micro- 
organisms were the only considerations involved, freezing at a temperature 
below about — 10° C. would be an ideal method of preservation. At this 
temperature fresh meat will remain wholesome for a year or more, but 
bacon deteriorates more rapidly through oxidative changes in the fat. 
The problem of storing meat appears then to be solved, the application 
of cold at — 10° C. being the solution. Unfortunately, however, freezing 
itself produces changes which damage the meat to some extent, and though 
the damage may only be in appearance and is negligible in mutton, lamb and 
pork, it is considered by the trade to render freezing, as distinct from 
chilling, an unsatisfactory process for beef. 
Drip.—tLet us consider what happens to meat when it is frozen. One effect 
of freezing is similar to that of drying ; both remove water, but whereas in 
drying the water is entirely removed, in freezing it remains in the tissue in 
the form of ice, and is thus free to be reabsorbed when the tissues are thawed. 
The proportion of water frozen out of the tissues depends on the tempera- 
ture. In the case of muscle it is about 17 per cent. at a temperature of 
—1°C.,and about 98 percent. ata temperature of — 20°C. The ice is in the 
form of crystals, and the size of the crystals depends, not on the temperature 
alone, but more particularly on the rate of freezing. When meat is frozen 
slowly, the bulk of the ice is formed between the muscle-fibres and the 
crystals are large ; such crystals have a disruptive effect upon the fibres, 
and the result is that when the meat is thawed the water is not entirely 
reabsorbed but partly drains away, carrying with it dissolved protein, salts 
and pigments. ‘This is unsatisfactory. But as the rate of freezing is 
increased, less and less ice is formed between the muscle-fibres and more 
and more within them, and the size of the ice crystals is also diminished. 
The result is that when meat is frozen at a rapid rate, since there is more 
moisture reabsorbed on thawing, the ‘ drip,’ as it is called, is less when the 
meat is thawed. It should therefore be possible, by increasing the rate of 
freezing, to form the whole of the ice within the muscle-fibres and none 
between them, and in such case there would be no ‘ drip ’ at all on thawing. 
This reasoning is perfectly sound, but the requisite rate of freezing is so 
high that it is unattainable in pieces of meat thicker than about 24 in., 
and quick freezing is therefore applicable only to small cuts, such as chops 
and steaks. Moreover, not only must the rate of freezing be high, but the 
temperature of storage must also be maintained at a far lower, and therefore 
more expensive, level than is usual, for it is a well-known physical fact that, 
even when small ice crystals are formed, they tend to grow at the expense 
of their fellows, and the rate at which they grow increases with the 
