CHARLES THOM 441 



may be withdrawn by the addition of an agent like salt or sugar while the rest becomes 

 a brine or syrup sufficiently concentrated to reduce or stop losses. The combination 

 of reduced water content and salting is the basis of most brining processes with meat 

 and fish. The combination of sugar with the juices of fruit products is used in the 

 manufacture of preserves, jams, jellies, etc. In the development of these industries 

 concentrations capable of controlling the usual processes of decay are readily reached, 

 but along with these developments species of bacteria, yeasts, and molds capable of 

 growing in solutions of salt or sugar verging upon saturation have complicated the 

 processes. Salt-tolerant organisms often invade the tissues of meat and fish, discolor- 

 ing them and rendering them unfit for use. Molds and yeasts tolerant of high concen- 

 trations of sugar break down the sucrose of stored raw sugar, invert maple sugar, and 

 ferment the centers of many forms of confectionery causing tension and bursting 

 which renders them unmarketable. 



We are only beginning to appreciate the bacteriological precautions necessary in 

 the handling of foods which depend upon osmotic concentration for extension of their 

 marketing period. The development of this information bids fair to bring about clean- 

 er and more sanitary handling of all these foods as a measure in the prevention of loss, 

 as well as in the interest of the consumer. 



PRESERVATION BY COLD 



The whole practice of refrigeration rests upon the progressive slowing of met- 

 abolic activities by lowered temperatures. The response of the different species 

 of micro-organisms to low temperature is exceedingly varied. In studies of meat 

 in transit from Australia and New Zealand to London, Brooks' found that cer- 

 tain molds would develop characteristic colonies at temperatures down to -{-22° F. 

 Pennington and her colleagues in the Bureau of Chemistry, working with bacterial 

 cultures (unpublished), showed that the micro-organisms used would grow slowly 

 at temperatures below the freezing-point as long as crystallization of the sub- 

 stratum did not occur. No growth was found by them in tubes in which crystalliza- 

 tion occurred quickly in the cold-storage chamber used. Since the usual temperatures 

 of the refrigerator leave the products unfrozen, we must recognize that storage in 

 such conditions is not indefinite preservation, but such a slowing up of inherent de- 

 terioration of the product and of micro-organic activity as will prolong the market- 

 ing period for days, weeks, or months according to the conditions furnished. We must 

 recognize further that the products removed from the refrigerator are not fresh prod- 

 ucts, however good and fit for food they may be, and that they ultimately become 

 unfit even under the most careful handling in the refrigerator. This is well illustrated 

 by the deterioration of eggs in storage. Eggs are stored just above the freezing-point, 

 and show progressive changes differing in rate in the same lot so that there is an in- 

 creasing percentage of unmarketable eggs in lots removed from storage month by 

 month. These losses become so large as to limit the period of profitable storage to less 

 than a year. Even within that time the discriminating user of eggs recognizes their 

 deterioration within a comparatively short period. 



' Brooks, F. T., and Hansford, C. G.: "Mould Growth upon Cold-store Meat." Tr. Brit. Mycol. 

 Soc, VIII, Part III (1923), 113-42. 



