REPORT OP COMMITTEE ON PUBLICATION 299 



The averages for the three seasons show remarkable uniformity through- 

 out. The grand averages for all shipments of the three years are an index 

 of the effect of the pre-cooling treatment upon this class of fruit. The 

 differences in percentages of decay are only slight, although in favor of the 

 pre-cooled lots. The decay in all lots is too high for good marketable condi- 

 tion. The average percentages found in the fruit two days after arrival are 

 identical, and after four days very nearly identical in pre-cooled and non- 

 pre-cooled shipments. The slight difference between 6.5 per cent and 8.1 per 

 cent in favor of the pre-cooled shipments on arrival is not sufficient to justify 

 the extra expense of the pre-cooling process, from the standpoint of the 

 effect upon the carrying quality of the fruit. In fact, in a number of indi- 

 vidual shipments the average percentages of decay were actually higher than 

 was found in corresponding non-pre-cooled shipments. This does not neces- 

 sarily mean that the pre-cooling of grapes is harmful. It does mean that 

 there are other factors which must be taken into consideration, and pre- 

 cooling alone cannot be depended upon to avoid excessive deterioration in 

 grape shipments. 



One possible explanation for the increase in decay in pre-cooled ship- 

 ments over non-pre-cooled and the slieht differences shown in the averages 

 was thought to be the uneven cooling which necessarily takes place in the 

 cooling of the different parts of the car after it is loaded. It is easy to see 

 that it is practically impossible to have the air blast reach uniformly to all 

 parts of the load. The crates must be closely stacked, thus interfering 

 materially with the circulation of the air currents within the car. The fruit 

 most exposed to the blast will be cooled below the freezing point of the fruit 

 long before the crates in the body of the load are materially affected. There- 

 fore, as soon as the exposed crates reach the danger point, the work must 

 cease. Equalization of the temperature conditions must then be depended 

 upon to bring the average temperature of the load down to the desired 

 point. It is conceivable that the extra cooling and following rise in tempera- 

 ture might be detrimental to the keeping quality of the affected packages. 

 It has not been possible actually to test this hypothesis by experimental data. 

 During one season, however, a comparison of car pre-cooling with the ware- 

 house system was made, but the results did not show that there was any 

 material gain by handling the fruit in this way. 



Later investigations of the temperature conditions within the refrige- 

 rator cars while en route indicate that the relative inefficiency of the insula- 

 tion used in the cars may be responsible for the inconsistent results. Tem- 

 perature records taken of cars en route show that there is a considerable 

 leakage of heat through the insulation, resulting in a rather rapid warming- 

 up of the fruit on the top tiers. The rise in temperature on these top tiers 

 is sufficient to account for the increase in the decay, especially where the 

 fruit has not been handled with sufficient care to prevent injury. A better 

 type of refrigerator car with better insulation is a necessity before the full 

 benefits of pre-cooling can be obtained. 



The most impressive lesson to be derived from these rather negative 

 results, however, is the fact that pre-cooling cannot replace proper handling. 

 It cannot be depended upon to offset the decay which inevitably follows in 

 juries to the fruit. It is more expensive than careful handling, and in addi- 

 tion is less efficient in preventing decay. Pre-cooling is, however, a legiti- 



