Nov. 15, 1920 Changes Taking Place in the Tempering of Wheat 275 



The addition of sufficient water to make the total moisture content 18 

 per cent was tried with each variety of wheat. In every case the result- 

 ing flour was sticky, the sieves became clogged, and the yields were 

 reduced below that for the untempered grain. For this reason the 

 analyses of the flour from this treatment were not completed. 



It will be noted that when the wheat was tempered at 5 C. there was 

 practically no chemical change as compared with the untempered wheat. 

 As a general rule the yields were slightly higher and the milling qualities 

 were considerably better than those secured from the control or un- 

 tempered wheat. In each case the bran was tougher, and a cleaner sepa- 

 ration of the bran and endosperm was possible. The length of time 

 appeared to have very little influence on either the physical or chemical 

 composition of the flour. 



When the wheat was tempered at 20 C, a small but definite chemical 

 change took place. The hydrogen-ion concentration was increased, as 

 was shown by a lower P H value. The total acidity, the water-soluble 

 phosphorus, and the titrable nitrogen were also higher. Both the yield 

 and the milling quality were better than when the wheat was tempered 

 at 5 C. The time of tempering appeared to be a factor in the chemical 

 changes but had very little if any relation to the physical qualities. 



The chemical changes were still more pronounced when the grain was 

 tempered at 40 C. The physical changes appeared to be detrimental to 

 the milling qualities of the grain. In other words, increasing the time of 

 tempering increased the chemical changes but proved detrimental after 

 48 hours so far as the milling value of the wheat was concerned. 



In general the milling qualities of the drier wheats were improved by 

 tempering more than were those of the wetter wheats, and the hard wheats 

 were improved more than the soft wheats. 



It may be concluded from these experiments that slight chemical 

 changes take place during the tempering process and that these changes 

 increase with time and temperature. Improvement in the milling qualities 

 is confirmed also, excepting in cases where the time of tempering exceeded 

 48 hours and where the temperature exceeded 20 C. It would appear 

 from this that (1) the improved milling quality of tempered wheat is due 

 chiefly to physical changes, (2) a temperature of 20 to 25 C. is best, (3) 

 i$/4 per cent moisture appears to be about the best, (4) the maximum 

 improvement takes place in 48 hours, (5) hard wheats are improved more 

 than soft wheats, and (6) dry wheats are improved more than wet 

 wheats. 



