Diglyceride production via noncatalyzed esterification of glycerol and oleic acid

Abstract

Production of diglycerides (DG) plays an important role in food, pharmaceutical, and cosmetic industries. In this study, optimal conditions for DG synthesis via noncatalyzed esterification of oleic acid with glycerol were determined. The temperatures (150°C, 175°C, and 200°C), oleic acid to glycerol molar ratios (1:1, 2:1, 3:1, and 4:1), and initial water content were varied to determine DG selectivity and % conversion over an 8‐hr period in a nitrogen‐purged system. The results exhibited a similar trend to catalyzed studies wherein an increase in temperature and molar ratio leaned towards the production of triglycerides (TG). It was also noted that tested initial water contents had an insignificant effect on reaction rates and product selectivity. Addition of molecular sieves for removal of water also resulted in negligible effects within this temperature range. DG production is optimum at 175°C and 2:1 molar ratio at 4 hr resulting in a product containing 42.6 ± 0.92 wt.% DG and a process selectivity of 1.11 ± 0.06 g DG/g (monoglycerides + TG). Purification by silica gel column chromatography of the product with the highest selectivity resulted in an enriched mixture with a yield of 58.25% and purity of 86.95 wt.% DG. Compared with catalyzed reactions, this system would require less downstream processing as removal of catalysts is not required and saponification does not occur. Although this procedure involves higher reaction temperature compared with enzyme‐catalyzed reactions, the time required to obtain high conversion is much shorter.

Synthesizing Precursors for Functional Food Structured Lipids from Soybean Oil Deodorized Distillates

“…Apart from these, the equivalent ξ OA and ξ GlyOH at the stated time ranges also have similar values of 37.69% and 99.98% at 40 °C, 37.88% and 93.51% at 50 °C, and 39.68% and 100% at 60 °C. Similar trends were observed in the esterification of OA and glycerol at initial molar ratios of 2.0-4.0, carried out between 40 and 60 °C but in the presence of 15% Lipozyme TL IM (w/w OA ), the solvent toluene, and molecular sieves [20], as well as, in noncatalyzed solvent-free systems at the same molar ratios but at a higher temperature range of 150-200 °C [31]. The peaks of DG selectivity also occurred faster within a narrow time frame as the reaction temperature was increased, although their occurrences were observed at much shorter periods (> 4 h) alongside steep increases in TG because of a higher enzyme loading in the former and higher temperatures in the latter compared to the current study.…”

“…in several studies on DG production based on esterification processes [31,49]. The DG yield (Y DG ) is another response that is important to consider as it gives a more practical basis of process efficiency.…”

“…It is noted that silica gel has been used as an adsorbent for glycerol and the resulting material utilized as a glycerol reservoir to regulate its release in the glycerolysis of TG [30]. It also known to adsorb different classes of lipids at various degrees, more strongly with partial glycerides, making it useful in lipid separation [31]. These could compete with the adsorption of water during solventfree esterification.…”

Process evaluation of solvent‐free lipase‐catalyzed esterification schemes in the synthesis of structured triglycerides from oleic and palmitic acids

“…Preferably, a solvent‐free method of purification such as molecular distillation can be employed to separate FFA 29 and PG 30,31 from TG and make it suitable as a human milk fat substitute (HMFS). In this study, separation by column chromatography 20 followed by winterization was attempted to purify OPO in the crude product from the current process. A fraction with TG purity greater than 98 wt.% but with a recovery of approximately 65 wt.% can be obtained from silica gel separation.…”

“…The analysis of fatty acids and glycerides was performed using a GC unit (Shimadzu GC‐2010 Plus equipped with a split injector and FID), which was run on the program described in the work of Ting et al 20 A ZB‐5HT Inferno column (15 m × 0.32 mm × 0.1 μm) was installed in the unit for component separation. The conditions in the analysis were as follows: injector and detector temperature at 370°C, initial column temperature at 80°C ramped to 365°C at 15°C/min, nitrogen gas flow of 1.4 ml/min, and an injection split ratio of 50.…”