Monoacylglycerol production

Damstrup ML, Abildskov J, Kill S, Jensen AD, Sparsp FV, Xu X. Evaluation of binary solvent mixtures for efficient monoacylglycerol production by continuous enzymatic glycerolysis. J Agric Food Chem 2006 54 7113-7119. 

Damstrup ML, Jensen T, Spars0 FV, Kill SZ, Jensen AD, Xu X. 2005. Solvent optimization for efficient enzymatic monoacylglycerol production based on a glycerolysis reaction. J Am Oil Chem Soc 82 559-564. 

Rosu R, Uozaki Y, Iwasaki Y, Yamane T. 1997. Repeated use of immobilized lipase for monoacylglycerol production by solid-phase glycerolysis of ohve oil. J Am Oil Chem Soc 74 445-450. 

Monoacylglycerols are the monoesters of glycerol that consist of only one fatty acid attached either to the position 1(3) or 2 of the glycerol backbone. However, because both diacylglycerols and monoacylglycerols are hydrolytic products of triacylglycer-ols and phospholipids, they may be present, if any, only in negligible levels in animal and plant tissues. 

The products of triacylglycerol digestion, mainly monoacylglycerol and long-chain fatty acids, interact with bile salts to form micelles, which comprise bile salts/ monoacylglycerols/phospholipids and fatty acids. The micelle aids the absorption of monoacylglycerol and fatty... 

Fats are esters of the trivalent alcohol glycerol with three fatty acids. When a single fatty acid is esterified with glycerol, the product is referred to as a monoacylglycerol (fatty acid residue = acyl residue). 

Correct answer = A. Pancreatic lipase hydrolyzes dietary triacylglycerol primarily to 2-monoacylglycerol plus two fatty acids. These products of hydrolysis can be absorbed by the intestinal mucosal cells. Bile salts do not inhibit release of fatty acids from triacylglycerol, but rather are necessary for the proper solubilization and hydrolysis of dietary triacylglycerol in the small intestine. Short- and medium-chain length fatty acids enter the portal circulation after absorption from the small intestine. Synthesis of apolipoproteins, especially apo B-48, is essential for the assembly and secretion of chylomicrons. 

The products of lipid digestion—free fatty acids, 2-monoacylglycerol, and cholesterol—plus bile salts, form mixed micelles that are able to cross the unstirred water layer on the surface of the brush border membrane. Individual lipids enter the intestinal mucosal cell cytosol. 

Monoacylglycerols and diacylglycerols may be genuine membrane constituents or may be products of lipolysis. Unesterified fatty acid levels... 

Studies in vitro and in rats showed that short and medium chain fatty acids and monoacylglycerols hydrolyzed from milk triacylglycerols and digestion products of sphingolipids possess strong anti-bacterial and anti-viral properties. 

Milk fat contains a number of different lipids, but is predominately made up of triacylglycerols (TAG) (98%). The remaining lipids are diacylglycerols (DAG), monoacylglycerols (MAG), phospholipids, free fatty acids (FFA) and sterols. Milk fat contains over 250 different fatty acids, but 15 of these make up approximately 95% of the total (Banks, 1991) the most important are shown in Table 19.1. The unique aspect of bovine, ovine and caprine milk fat, in comparison to vegetable oils, is the presence of high levels of short-chain volatile FFAs (SCFFA), which have a major impact on the flavor/aroma of dairy products. Most cheeses are produced from either bovine, ovine or caprine milk and the differences of their FFA profile are responsible for the characteristic flavor of cheeses produced from such milks (Ha and Lindsay, 1991). 

Figure 26-5. Principle of the 13C-mixed triglyceride breath test. Absorption of 13C-mixed triglycerides requires prior hydrolysis by pancreatic lipase (1), which leads to production of free fatty acids (stearic acid) and monoacylglycerol [2-(l-13C)octanoylglycerol]. These metabolites are incorporated into micelles, absorbed, and transported to the liver (2). Further degradation by hepatic enzymes and P-oxidation results in formation of 13C02, which is absorbed into the bloodstream, transported to the lung, and exhaled (3). Thus, exhalation of 13C02 reflects intestinal lipolysis and is a marker of pancreatic exocrine function.

Thus biodiesel is a better lubricity enhancer than its parent vegetable oil because of the presence of high-lubricity species, some of which, such as monoacylglycerols, can arise during biodiesel production. Biodiesel is required at levels such as 2% for lubricity enhancement in order to achieve a sufficient additive level of high-lubricity materials in petrodiesel. Table 1.17 gives data showing the effect of minor components of biodiesel on its lubricity. 

The lipases digest the triacylglycerols into free fatty acids and monoacylglycerol (Figure 22.4). These digestion products are carried in micelles to the intestinal epithelium where they are absorbed across the plasma membrane. 

In many food products and even some processing operations, it is important to be able to control lipid crystallization to obtain the desired number, size distribution, polymorph, and dispersion of the crystaHine phase. In most foods, it is crystallization of triacylglycerols (TAG) that is most important, although, at times, crystallization of other lipids (i.e., monoacylglycerols, diacylglycerols, phospholipids, etc.) may also be important to product quality. 

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