294 III. CHEMISTRY OF NEUTRAL FATS 



lower alkyl esters of gallic acid including propyl gallate is covered by a 

 patent.^2^ Norris and Riemenschneider^^^ have recently reported the 

 synthesis of the hexyl, octyl, dodecyl, tetradecyl, hexadecyl, and octadecyl 

 esters of gallic acid. 



Gallic acid itself has been shown by Olcott and MattilP^" and by Golum- 

 bic and MattilP^* to have effective antioxidant properties. Thus, the in- 

 duction period of lard as determined by the oxygen absorption at 75°C. was 

 prolonged from 12 hours to 213 hours by the addition of 0.06% of the acid. 

 Gallic acid has also been shown to exert a synergistic action on other anti- 

 oxidants, and for this reason it should find an application in the protection 

 of vegetable as well as of animal fats. As yet there is no proof of its in- 

 nocuousness, and therefore its use has not been approved. It is quite in- 

 soluble in fats, although it dissolves to a sufficient extent to exert its anti- 

 oxidant effect.^^2 The stabilizing effects of gallic acid on fats have been 

 demonstrated by Filer et al.^^^ and by Mattil et al.^^"^ 



{g) Tannins and Tannic Acid. Spannuth, McGuine, and Crapple^^* 

 have found that tannins are excellent antioxidants. When added to lard 

 they have protective factors (ratios of keeping time with antioxidant to 

 keeping times of controls) varying from 2.5 to 6.2. The antioxidant activ- 

 ity is presumably related to the gallic acid present in tannins. Several 

 patents cover the use of tannins and tannic acid in fats.^^^'"" 



(h) Ascorbic Acid and Its Esters. Golumbic and Mattill"^ have found 

 that ascorbic acid by itself is a relatively ineffective antioxidant in animal 

 fats, although it does have a synergistic action in connection with to- 

 copherol, hydroquinone, and similar products. The poor solubility of as- 

 corbic acid in fat has been overcome by the use of fat-soluble esters such as 

 ascorbyl palmitate. Although these esters are relatively inactive in animal 

 fats, they are especially satisfactory in vegetable fats, and they have a syn- 

 ergistic effect on the phospholipids and tocopherols.^^* The use of these 

 esters in fats has been patented.^'^ 



The retarding effects of some of the common antioxidants on the rate 

 of development of rancidity are summarized in Tables 41 and 42. 



6" T. Sabalitschka and E. Bohm (to Heyden Chem. Corp.) U. S. Patent No. 2,255,191 

 (Sept. 9, 1941). 

 62* S. G. Norris and R. W. Riemenschneider, J. Am. Chem. Soc, 68, 500-501 (1946). 



626 C. Golumbic and H. A. Mattill, Oil & Soap, 19, 144-145 (1942). 



"6 L. J. Filer, Jr., K. F. Mattil, and H. E. Longenecker, Oil & Soap, 21, 289-292 (1944). 



627 K. F. Mattil, L. J. Filer, Jr., and H. E. Longenecker, Oil & Soap, 21, 160-161 

 (1944). 



628 H. T. Spannuth, T. H. McGuine, and G. A. Grapple, Oil & Soap, 23, 110-113 (1946). 



629 S. Musher (to Musher Foundation), U. S. Patents Nos. 2,233,142 (Feb. 15, 1941) and 

 2,282,811 (May 12, 1942). 



630 B. J. Verbeck (to Wilson and Co.), U. S. Patent No. 2,354,719 (Aug. 1, 1944). 

 6" C. Golumbic and H. A. Mattill, J. Am. Chem. Soc., 63, 1279-1280 (1941). 



632 P. A. Wells and R. W. Riemenschneider (to Secretary of Agriculture), U. S. Patent 

 No. 2,368,435 (Jan. 30, 1945). 



