Oct. 1. 1919 Method for Measuring Acidity of Cereal Products 45 



and the other that the total original acidity of this oat is included in the 

 value found for the 60-minute extraction and that the rise upon pro- 

 longed extraction is due to ferment action. From my present experience 

 I would prefer the latter explanation. While, as shown above, no acid- 

 producing ferments come into play in the filtered, unneutralized grain 

 extracts at the cold-storage temperature, it is quite conceivable that if 

 the liquid remains in prolonged contact with the grain solids some 

 insoluble constituents may be hydrolized by specific ferments and form 

 acid-reacting, soluble cleavage products. 



It would be difficult to understand why the total acids originally 

 present in oats should not dissolve within i hour and hence should not 

 be included in the 60-minute acidity value, in view of the fact that, as 

 Thatcher and Koch {16) have shown, all of the diastase of cereal products 

 can be brought into solution by a i-hour extraction with ice water. 

 Diastase, being a colloid, is considered soluble with some difficulty, 

 while acid-reacting substances which occur in nature are known to be 

 readily soluble in water. 



From the corn meal acidities recorded in Table IV it would appear 

 that for corn meals the extraction period in the ice-water method should 

 be longer than for oats. For the experiment I used a commercial white 

 corn meal which was sufficiently fine to be passed through a 20-mesh 

 sieve. Notwithstanding this fineness slightly more than i hour's time 

 appeared to be required to dissolve with ice water all of the acid contained 

 in this meal. It follows that the extraction period should be extended 

 to I K hours for corn possessing this degree of fineness. 



On the whole it may be said that the ice -water extraction method 

 afifords a very rapid and inexpensive means for determining the original 

 quantity of free acids contained in cereal products, and the method is 

 no doubt of wide applicability. The results obtained by its use are 

 sufficiently accurate for practical purposes. At the same time it permits 

 the experimenter to devise such modifications as may suggest themselves 

 in special cases. For practical routine work the use of a cold-storage 

 room can, of course, be easily dispensed with by immersing the tightly 

 stoppered extraction bottles in a vessel with ice water. In the work of 

 Mr. Mastin, who, as stated, is responsible for the acidity figures recorded 

 in Table II, this mode of operation was employed. It was also found 

 preferable to use a NI20 solution of sodium hydroxid for the titrations. 

 In general, the following suggestions for the successful operation of the 

 method may be given : 



APPARATUS AND REAGENTS REQUIRED 



1. A flat-bottomed pan, with walls at least 12.5 cm. high, which is kept filled with 

 ice water. 



2. Extraction bottles of ordinary glass, provided with well-fitting rubber stoppers. 



3. Graduated cylinders, capacity 100 cc. 



4. Glass funnels. 



5. Wide-mouthed beaker flasks, capacity 100 cc. 



6. Folded filter paper. 



