100 



Journal of Applied Microscopy. 



somewhat below 20''C. The microtome 

 knife or razor must be very hard, sharp, 

 and rigid, for the material is now brit- 

 tle to a greater degree than most plant 

 tissues. Staining on the slide by any of 

 the usual methods is easy and the results 

 satisfactory. 



George J. Peirce. 

 Assistant Professor of Plant Physiolo- 

 gy, Stanford University, California. 



A Note on the Detection of Maize 

 Starch and Maize Flour in Mix- 

 ture With Wheat Flour. 



E. E. EWELL. 



Contributed by H. W. Wiley. 



During the past few months there has 

 been much discussion in commercial and 

 legislative circles concerning the use of 

 maize products for the dilution of wheat 

 flours. It is claimed that the addition 

 of a well prepared maize starch to 

 wheat flours increases the power of the 

 latter to endure storage in warm and 

 moist climates in exactly the same way 

 that an addition of starch to a baking 

 powder insures its keeping qualities. 

 On the other hand, it has been urged 

 that a considerable portion of the dilu- 

 tion of wheat flour with maize products 

 is done with a less praiseworthy mo- 

 tive. It seems to be a fact that the sale 

 of wheat flours adulterated with maize 

 is still largely confined to Southern 

 markets. Two samples of flour which 

 were suspected of containing maize have 

 been sent to us for examination from 

 the Gulf states. Both contained a con- 

 siderable proportion of maize starch. On 

 the other hand, we have just finished 

 the examination of forty samples of 

 fiour of various grades, recently pur- 

 chased from wholesale and retail gro- 

 cers in Washington, D. C, including 

 some of the best stores in the city, as 

 well as small establishments in the 

 humbler quarters, and with two excep- 

 tions, found no evidence of admixture 

 with maize in any of the samples. In 

 both of these samples the maize was 

 present in small amount, and in the 

 form of rather coarsely ground particles. 

 In one of these cases the presence of the 

 maize was traced to careless storage in 

 the small store at which it was pur- 

 chased; as the other sample also con- 

 tained a number of whole grains of rice, 

 it is quite probable that its foreign 

 ingredients were accidentally added. 



The fact that maize products are used 

 to a considerable extent in some parts 

 of the country for the dilution of wheat 

 flours, for one purpose or another, makes 

 it desirable to develop the most conven- 

 ient and reliable methods for the detec- 



tion of such mixtures. Various methods 

 have been suggested for this purpose, 

 depending upon the "feel" of the flour 

 when dry and when kneaded with water, 

 etc., but the microscope must be consid- 

 ered the only instrument at present 

 known that will give reliable results in 

 every case. Wheat flours are not always 

 as flnely ground as many persons sup- 

 pose. Maize starch is added in the form 

 of ground white maize of various 

 degrees of fineness or in the form of 

 maize starch, which may be made from 

 maize of any variety, and which will 

 possess a "feel" varying with its phy- 

 sical condition, which is in turn depend- 

 ent upon the purity and method of man- 

 ufacture; and the amount of admixture 

 may vary within wide limits. All of 

 these circumstances tend to limit the 

 value of any test which does not enable 

 us to study the form and size of th:-. 

 individual starch grains of the material. 

 While the task of a microscopic exam- 

 ination is easier, the greater the per- 

 centage of the substance sought, very 

 small percentages of maize starch may 

 be very readily detected in wheat flours 

 if a thorough search is made. 



Dr. C. Urban Smith* has stated that as 

 low as two per cent, of adulteration can 

 be detected by this means. Our own 

 work indicates that this delicacy can 

 readily be attained or even exceeded; 

 this is especially true if the adulterant 

 is added in the form of high grade 

 maize starch. 



In many cases the microscopic exam- 

 ination may be greatly facilitated by 

 sifting the flour through bolting cloths 

 having meshes of different sizes, and by 

 examining each portion thus separated. 

 It must be remembered, however, that 

 the maize starch will not always accu- 

 mulate in the coarsest portions of the 

 sifted material. 



A mixture of equal volumes of water 

 and glycerol and fifty per cent, acetic 

 acidt have been suggested as mounting 

 media appropriate for the microscopic 

 examination of starches and fiours. The 

 diluted glycerol possesses the advantage 

 that it evaporates but very slowly; 

 acetic acid brings out the structures of 

 the foreign starch grains somewhat 

 clearer than do water or diluted glycerol. 



In consequence of the possibilities of 

 imperfect mixing and the danger of 

 missing coarse particles, it is important 

 to thoroughly mix the sample before 

 proceeding with the examination, and 

 to use a considerable portion of it for 

 preparing the mixture with the mount- 

 ing medium. To this end, place from 

 one to ten grams of the material in a 



* Health Magazine, 1898, 5, 286. 

 t Dr. C. Urban Smith, Health Magazine, 1898, 5, 

 286. 



