INFLUENCE OF RELATIVE HUMIDITY AND MOISTURE CONTENT. 9 



moisture content of the flour produced was 12 per cent, and at 65 to 

 69 per cent relative humidity, the moisture content was 13.3 per cent, 

 or an increase of 1.3 per cent moisture for a difference of 30 per cent 

 in relative humidity. 



It has been suggested that probably these are the normal moisture 

 contents for flour at the respective relative humidities shown, but 

 such a conclusion is not entirely justified, for the reason that in these 

 tests no proof exists that the exposure of the flour to the air, which 

 was limited to the length of time necessary for milling the sample, 

 was sufficiently long to establish a state of equilibrium between the 

 moisture content of the flour and that of the mill atmosphere. On 

 the other hand, proof that at least some of these moisture contents 

 are not normal is evidenced by the wide divergence from the results 

 obtained by Bailey, to which reference has been previously made. 

 For instance, he found that the hygroscopic moisture in flour in 

 equilibrium with atmospheric humidity at 25° C. ranges from a little 

 more than 5 per cent at 30 per cent relative humidity to 15 per cent 

 at 60 per cent relative humidity. 



COMPARISON OF THE INFLUENCE OF RELATIVE HUMIDITY AND 

 OF MOISTURE CONTENT OF WHEAT ON THE MOISTURE CON- 

 TENT OF FLOUR. 



Some indication of the comparative influence exerted on the mois- 

 ture content of flour by each of the factors, atmospheric humidity and 

 moisture content of the wheat before tempering, is given in figure 5. 

 In this figure the results from samples which before tempering had 

 moisture contents falling within various ranges are represented by 

 separate curves. From this system of grouping it is possible to ascer- 

 tain the particular influence exerted by each of these two factors. 

 The proximity of the four curves to each other and their tendency 

 to cross and recross each other indicate, for the method of tempering 

 used in these experiments, no very pronounced relation between the 

 moisture content of the flour and the moisture content of the wheat 

 before tempering; or, in other words, no relation to the quantity of 

 temper water added. On the other hand, a decided tendency is shown 

 for the moisture content to increase as the relative humidity increases, 

 a difference of 10 per cent in relative humidity making an average 

 difference of approximately one-half of 1 per cent in the moisture 

 content of the flour. 



It would be interesting to know what influence, if any, variations 

 in the final moisture content to which wheat may be tempered and the 

 length of the tempering period would have on the resultant moisture 

 content of the flour milled at different relative humidities. Since all 

 samples were tempered to the same moisture content and for approxi- 

 mately the same length of time, it is impossible to draw any conclu- 

 sions in regard to this influence from the results of these experiments, 



