Heat deterioration of phospholipids. VI. Clarification of mechanism for the new pseudo Maillard rearrangement reaction by using 2-aminoethyl dihydrogenphosphate

Clarification of the Mechanism of Inhibiting the Maillard Reaction between Phosphatidylethanolamine and Sugars by Adding Fatty Acid Calcium Salts

Lecithin is known to undergo heat induced deterioration by the Maillard reaction between 1 mol of any sugar, except 2-deoxy sugar, and 2 mol of phosphatidylethanolamine (PE). However, we have previously reported that adding fatty acid metal salts can inhibit heat deterioration of soybean lecithin (SL). To clarify the mechanism of inhibition, 1,2-di-O-stearoyl-sn-glycero-3-phosphatidylethanolamine (DSPE), d-glucose, and calcium stearate or calcium decanoate were heated in octane. When DSPE and d-glucose with calcium stearate or calcium decanoate were heated in the octane, the heat deterioration of DSPE was significantly inhibited, and no increase in UV absorption at 350 nm was observed. From these reactant solutions, one compound having a phosphate group and no primary amine was isolated, and NMR spectra confirmed that two molar of stearic acid derived from DSPE were coordinated to the amino group and phosphate group of DSPE. Therefore, we concluded that adding fatty acid metal salts reduced the nucleophilic reactivity of the amino group of PE and inhibited the Maillard reaction with sugars because two molar of fatty acid derived from PE coordinated to the amino group and phosphate group of PE.

Use of Fatty Acid Metal Salts for Preventing Maillard Reaction-Driven Browning of Lecithins

We previously reported that fluid soybean lecithin (SL) undergoes heat deterioration by the newly reported pseudo-Maillard rearrangement reaction. To inhibit heat deterioration, SLs were treated with metal silicates, such as magnesium silicate and calcium silicate. When soybean fatty acid was added to SL before treatment with calcium silicate, the color index after heating improved significantly as the acid value increased from 10 to 35 mg KOH/g. To elucidate the role of soybean fatty acid, calcium silicate treatment was carried out by adding several fatty acids to SL. Although saturated fatty acids had no effect on the heat deterioration of SL, unsaturated fatty acids were significantly more effective at inhibiting heat deterioration. Furthermore, for unsaturated fatty acids, it was confirmed that the calcium concentration increased in SL. Based on these results, several fatty acid metal salts were added to confirm whether heat deterioration while heating SL could be inhibited. It was observed that the heat deterioration of SL could be inhibited with fatty acid metal salts, regardless of whether the fatty acids were saturated or unsaturated and whether the metal was monovalent, divalent, or trivalent. Therefore, in this study, we clarified that the heat deterioration of SL could be inhibited by adding fatty acid metal salts to SL. Among sodium stearate, calcium stearate, magnesium stearate, barium stearate, and aluminum tristearate, the divalent fatty acid metal salts had a stronger inhibitory effect on heat deterioration than the monovalent and trivalent salts.