METHODS FOR STUDY OF DIGESTIBILITY OF LIPIDS 213 



ciilation of digestibility by the use of correction factors based upon the 

 weight of the feces may yield quite erroneous results. Under such con- 

 ditions, it is necessary first to correct the weight of the feces by sub- 

 tracting the weight of the indigestible fraction, which has previusly been 

 determined by an independent analysis. The correction factor for meta- 

 bolic lipid is obtained by multiplying the corrected weight of the feces 

 by the appropriate value. 



Table 7 illustrates the procedures used by Calbert et at? in the calcula- 

 tion of the total stearyl citrate and stearyl alcohol excreted in the feces 

 by dogs previously fed stearyl citrate. After the determination of these 

 values, it is possible to use them for the calculation of the digestibility of 

 fat and stearyl citrate, as shown in Table 7. "X.S.F." is the abbrevia- 

 tion used in Tables 7 and 8, and subsequently in the text, for the non- 

 saponifiable fraction. 



a. General Formulas for the Calculation of the Digestibility of Higher 

 Alcohols, Hydrocarbons, or Waxes. It is possible to calculate the diges- 

 tibility of higher alcohols or hydrocarbons, as well as of fats fed concomit- 



Table 7 



Determination of Proportion op Stearyl Citrate and of Stearyl Alcohol 



Excreted in Feces after Administration of Stearyl Citrate" 



Results on 

 Category dog 10 



Stearyl alcohol excreted: 



(a) N.S.F., total, mg. 219 



(6) N.S.F., control value, mg. 33 



(c) Stearyl alcohol, total, mg. (a - b) 186 

 Citric acid excreted: 



(d) As free acid (before hydrolysis), mg. 



(e) Combined (after hydrolysis), mg. 49 

 Distribution of stearyl alcohol: 



(/) Total, mg. (c) 186 



(g) Combined, mg. (Combined citric acid (e) X 281 (540/192)) 138 



(h) Free, mg. (/ - g) 48 



Calculation oi stearyl citrate hydrolyzed: 



(i) Total stearyl alcohol as stearyl citrate, mg. (Corrected stearvl 



alcohol X 1.29 (696/540)) * 240 



(j) Unhydrolyzed stearyl citrate, mg. (Combined citric acid (e) X 



3.63 (696/192)) 178 



(k) Hydrolyzed, mg. (i — j) 62 



(I) Hydrolyzed, % (k/i X 100) 25.8 



Calculation of stearyl citrate and stearyl alcohol in feces: 



(to) N.S.F., total, g. (by analysis) 16. 1 



(n) N.S.F., corrected, g. (Control N.S.F. (17.2% dried feces) sub- 

 tracted from to) 13.2 

 (o) Stearyl alcohol and stearyl citrate in feces, g. (7? X + (100 — 



I) X n X (696/540) 16.0 



C. E. Calbert, S. M. Greenberg, G. Kryder, and H. J. Deuel, Jr., Food Research, 16, 

 294-305(1951). 



