jgii] Carl L. Aisberg 127 



The Occurrence of Lipase in the Fat of the Common 

 Fowl — Gallus Domesticus 



M, E. PENNINGTON AND J. S. HEPBURN 



(Food Research Laboratory of the Bureau of Chemistry, U. S. 

 Department of Agriculture, Philadelphia.) 



If a chicken be kept hard frozen or at the temperature of the 

 room, or at any temperature between these two extremes, the 

 acidity of the fat increases, as has been shown in previous pubhca- 

 tions from this laboratory. Since the fat-spHtting enzyme, hpase, 

 is found in many plant and animal tissues, this investigation was 

 undertaken to determine if lipase is present in the crude fat of 

 chickens. The technique is fairly simple. The crude abdominal 

 fat is passed several times through a meat chopper, and its acidity 

 is determined. A weighed sample of the ground fat is triturated 

 in a mortar with sand, and then extracted with ten times its weight 

 of water. Fifty c.c. of the aqueous extract and i c.c. of an ester 

 (ethyl acetate, butyrate or benzoate, or amyl salicylate) are mixed, 

 the Solution is made neutral to Phenolphthalein and incubated at 40° 

 C. for periods of time varying between 24 and 168 hours — usually 

 y2 hours. Toluol is used as a bactericide. Fifty c.c. samples of 

 the aqueous extract are boiled, then run as blank experiments in 

 exactly the same manner as were the determinations proper. At 

 the end of the incubation both determinations and blank experi- 

 ments are titrated; the increase in acidity of the determination 

 proper over the blank is due to the action of lipase. 



This research has demonstrated the presence of lipase in the 

 crude abdominal fat of fresh chickens retaining the animal heat, and 

 of chickens kept at temperafures from that of the room to that 

 of the " f reezer " for varying periods of time. The highest acidity 

 of the crude fat, and the greatest activity of the lipase, occurred 

 in chickens which had been kept hard frozen for sixteen months, 

 or which had been permitted to putrefy at room temperature. The 

 lowest acidity of the crude fat, and the least activity of the lipase, 

 were found in a fresh chicken still retaining the animal heat. Ap- 

 parently in fresh birds the enzyme is present as a zymogen, which 

 is converted into the active form as the chicken ages after death. 



