THE PRESERVATION OE EOOD BY COLD 477 



short periods, and the seasonal variation in price is sufficient to warrant 

 its storage from summer to winter. The keeping qualities of butter 

 depend upon many factors,* and the most efficient cold storage cannot 

 compensate for previous deficiencies. In refrigerated butter there is a 

 gradual diminution in the total number of living bacteria, with possibly 

 a multiplication of a few particular kinds. There is a slow increase in 

 acidity. In frozen butter the bacterial content and the chemical com- 

 position remain practically unchanged. 



Fruits and Vegetables. — These foods are for the most part 

 adapted to preservation for short periods at ordinary temperatures, 

 and cold storage at a temperature slightly above zero is very effective 

 in diminishing the rate of change in them. The humidity of the storage 

 chamber should be kept constant at about 60 per cent saturation in 

 order to diminish evaporation as far as possible without favoring the 

 development of molds. These foods generally remain alive during 

 storage and the changes due to intrinsic enzymes are often important. 

 Some fruits need to undergo further ripening in storage before they are 

 ready for consumption and this change may be accelerated or delayed 

 by changing the temperature of the storage chamber. The develop- 

 ment of bacteria and molds with consequent rotting is best delayed by 

 maintaining dry clean fruits and vegetables in an atmosphere of very 

 constant humidity and very constant temperature slightly above the 

 freezing-point. 



Legal Control of the Cold-storage Industry 



At present there is a rather widespread prejudice against cold-stor- 

 age food products, and in soine respects this is not without justification. 

 Cold storage preserves so well the external appearance of fresh foods 

 that deception in the sale of them to the consumer is too frequently 

 practised. This is extremely unfortunate for aU parties concerned in 

 such transactions. The proper branding of all cold-storage foods, 

 clearly indicating their character and the length of time held in stor- 

 age, would ultimately benefit the producer, the consumer and also the 

 cold-storage industry. Where cold storage is efficient such a practice 

 would proclaim its efficiency. Where it is inefficient the cold-storage 

 industry can ill afford to allow the consumer to be deceived concerning 



* See chapter on the microbiology of butteri 



