Lipolysis partial glycerides

Gas-Liquid Chromatography. Gas-liquid chromatography (GLC) affords both a qualitative and, if adequate internal standards are used, a quantitative analysis of the products of lipolysis. It is necessary, however, first to isolate the acids by a suitable method and then to inject them as free acids or as esters. The partial glycerides can be isolated by thin-layer chromatography and can also be determined by GLC of suitable derivatives. The acid(s) remaining in the partial glycerides can be identified readily by GLC following transesterification. Jensen and co-workers have utilized these techniques in their studies of lipase specificity (Jensen et al 1964). 

Lipolysis, the enzymic hydrolysis of milk lipids to free fatty acids and partial glycerides, is a constant concern to the dairy industry because of the detrimental effects it can have on the flavor and other properties of milk and milk products. However, free fatty acids also contribute to the desirable flavor of milk and milk products when present at low concentrations and, in some cheeses, when present at high concentrations. 

Partial hydrolysis of lipids occur during digestion under the influence of lipases (Sections 11.2 and 11.3). Lipases present in seeds also promote hydrolysis, so that most extracted lipids contain some free acid and some partial glycerides. This is an undesirable change, since removal of free acid during processing is accompanied by some loss of fat. Lipolysis can be minimized by inactivation of the lipase before extraction. Enzymic deacylation is also the basis of some valuable analytical techniques (Section 6.2.17). 

Hydrolysis of esterified lipids is essential in order for lipid absorption to occur. Anatomically, lipolysis begins in the stomach where a limited amount of partial hydrolysis of triglycerides provides more polar lipids (fatty acids and partial glycerides) to assist in emulsification. A lingual lipase is thought to be involved in this process. The net result of this gastric phase of fat digestion is the initiation of lipolysis and the preparation of a stable emulsion on which the major pancreatic lipolytic enzymes can act in the milieu of the small intestine. 

---