Monitoring cyclic acyloxonium ion formation in palmitin systems using infrared spectroscopy and isotope labelling technique

Abstract

To confirm the possible involvement of acyloxonium ions as reactive intermediates in food related lipids, their formation was monitored in triplamitin, 1,2 dipalmitin, 1-monopalmitin and specifically labelled tripalmitin (1,1,1-13 C 3 ) using Fourier-transform IR spectroscopy (FTIR). Reactions were conducted at 1008C using a mixture of ZnCl 2 and the lipids. When tripalmitin or 1,2-dipalmitin samples were heated at 1008C in the presence of ZnCl 2 a new band centred at 1651 cm À1 was formed and increased over time. When 13 C-labelled tripalmitin (1,1,1-13 C 3 ) was studied the spectrum exhibited an expected 40 cm À1shift from 1651 to 1611cm À1 indicating the involvement of the carbonyl carbon in the formation of the band. The 1-monopalmitin generated a similar but weaker band at higher temperatures and requiring longer times. These observations may indicate that under hydrophobic environment acyloxonium ions are preferentially formed with neighbouring ester groups assisted by the catalytic action of a free hydroxyl group serving as a proton transfer site. In the absence of such a free hydroxyl group tripalmitin undergoes acyloxonium ion formation at a slower rate than 1,2-dipalmitoyl glycerol, whereas, 1-monopalmitoyl glycerol due to the absence of a neighbouring ester shows even slower transformation efficiencies. This order of reactivity may however change in the presence of water.

Chloropropanols, Chloropropandiols and Their Esters in Food – Formation, Occurrence, Determination, Reduction of Content

“…Glicydol (2,3-epoksy-propan-1-ol) w obecności HCl i pod wpływem ciepła może ulegać interkonwersji pomiędzy 3-MCPD i 2-MCPD. Mechanizmy powstawania MCPD i DCP oraz ich estrów zostały przedstawione w wielu publikacjach [9,14,34,59,60,67,71]. Analizowana jest także możliwość udziału związków chloroorganicznych rozpuszczalnych w fazie olejowej w powstawaniu 3-MCPD i jego estrów [53,58].…”

“…>150 °C i w warunkach symulujących odwanianie triacyloglicerole (TAG), czyli główny składnik olejów roślinnych, są najbardziej reaktywnymi substratami w reakcjach powstawania diestrów MCPD. Rahn i Yaylayan [60] przedstawili spektroskopowe (IR) dowody na to, że w temp. 100 °C tripalmitynian glicerolu tworzy jon acylooksoniowy, reagujący z anionem chlorkowym do estrów 3-MCPD (rys.…”

The effects of physical refining on the formation of 3-monochloropropane-1,2-diol esters in relation to palm oil minor components

“…A recent mechanism study revealed that the formation of 3-MCPD esters in a hydrophobic environment, via acyloxonium ion formation, can activate lipids toward the nucleophilic attack of chloride ions, which is applicable to the formation of chloroesters during the refining of vegetable oils (Rahn & Yaylayan, 2011b). The formation of acyloxonium ion from a related precursor is influenced by the steric hindrance effect and the leaving group involved.…”

“…Among the proposed precursors are partial acylglycerol (mono-and di-acylglycerol) (Rahn & Yaylayan, 2011b), phospholipids (Collier et al, 1991;Hamlet et al, 2004), and carotenoids (ILSI, 2009). Use of a D-optimal design modelling of the experiment (involving a categorical factor) is possible with a reduced number of experimental sets (Hoskins, Colbourn, & Montgomery, 2005).…”

Tallow Beef Flavor: Effect of Processing Conditions and Ingredients on 3‐Chloropropane‐1, 2‐Diol Esters Generation, and Sensory Characteristics

“…Previous researches reported a significant decrease of 3‐MCPD esters with addition of carbonate or bicarbonate salt into oil . In addition, Rahn and Yaylayan demonstrated that metal elements (such as iron, zinc, copper, etc.) existing in yeast extract, as Lewis acidic substances, can promote the formation of 3‐MCPD esters.…”