FACTORS AFFECTING RATE OF ABSORPTION 185 



what greater decrease was noted for straight hydrogenated cottonseed oil 

 melting at 46°C. A decrease in absorption rate to 20% of that of the value 

 for the limpid oils was observed with hydrogenated cottonseed oil melting 

 at 55 °C. Hydrogenated lard having an identical high melting point 

 showed a somewhat smaller depression in absorption rate. 



(3) The Presence of Emulsifying Agents 



It has recently been shown that the presence of emulsifying agents will 

 increase the rate of absorption and the coefficient of digestibility of difficultly 

 absorbed fats. Although these emulsifiers also appear to increase the speed 

 of absorption of readily absorbed fats such as limpid cottonseed oil, they 

 cannot improve the coefficient of digestibility, in view of the fact that these 

 fats, without the emulsifier, are practically completely digested. The 

 common emulsifying agents present in foods include lecithin, mono- and 

 diglycerides, polyoxyethylene sorbitan monooleate (PSM, marketed under 

 the trade name of "Tween 80"), and isopropyl and stearyl citrates. Not 

 only do these substances have an effect on the absorption of difficultly di- 

 gested triglycerides, but they also are quite effective in improving the utili- 

 zation of the fat-soluble vitamins, particularly vitamin A and carotene. 



a. The Effect of Lecithin on the Absorption of Fat. Commercial 

 lecithin has been widely employed as an emulsifying agent in a variety of 

 food products over the past decade. The presence of lecithin in a fat- 

 water mixture greatly aids in the emulsification of fat, and assists in the 

 production of very fine fat droplets. The beautiful fine emulsion which 

 exists in egg yolk is an excellent example of an emulsion of a natural fat 

 which is stabilized by lecithin. 



The formation of such a stable fine emulsion should increase the absorb- 

 ability of fat, irrespective of whether the Lipolytic or the Partition Hypoth- 

 esis represents the actual process by which fat is absorbed. The ad- 

 vocates of the Lipolytic Theory can explain any improved absorbability 

 when lecithin is present as a result of the production of a finer emulsion. 

 This will increase the ability of the fat to be hydrolyzed by the pancreatic 

 lipase, steapsin, since a greatly enlarged fat surface area is available to the 

 enzyme. On the other hand, if fat is absorbed largely in the form of drop- 

 lets of neutral fat, as is postulated in the Partition Theory, any agent which 

 will increase the capacity for the production of an emulsion, or which will 

 assist in the development of an emulsion system composed of finer droplets, 

 will aid in the absorption of fat. 



Adlersberg and Sobotka 838 reported that both fat and vitamin A are ab- 



838 D. Adlersberg and H. Sobotka, /. Nutrition, 25, 255-263 (1943). 



