Glycidols Esters, 2‐Chloropropane‐1,3‐Diols, and 3‐Chloropropane‐1,2‐Diols Contents in Real Olive Oil Samples and their Relation with Diacylglycerols

Abstract

A series of authentic virgin, refined, and mixtures of olive oils was analyzed for their content of 2‐and 3‐chloropropanediol (MCPD) esters expressed as 2−/3‐MCPD, glycidol (and related glycidyl esters) (GE), and diglycerides (DAG). High concentrations of MCPD and GE were found, above all, in pomace oils, which come from the poorer starting raw materials, while virgin olive oils, as expected, do not contain any process contaminant. On the other hand, DAGs are present in all samples, demonstrating that their involvement in the formation of such contaminants only occurs when temperatures are higher than that used during the refining steps. The lack of correlation between the amounts of MCPD and GE can be ascribed to their completely different chemical stability as the epoxy ring of the GE opens easily, leading to both short‐chain derivatives and/or MCPD itself. This finding can also explain the data about the absence of 2‐MCPD in all the analyzed oil samples: other than the statistical probability and the steric effect of the SN2 formation mechanism, both in favor of the 3‐ derivative, we have also to consider the MCPD formation pathway involving glycidol that, under opportune conditions of refining, can increase the whole amount of 3‐MCPD (under thermodynamic control, 3‐MCPD is more stable).

The Formation of 3-Monochloropropanediol Esters and Glycidyl Esters during Heat-Induced Processing Using an Olive-Based Edible Oil

“…The order of the effects was duration > temperature > DAG content. The previous studies also found that the role of DAG in the formation of 3-MCPDE and GE was not clear, but high temperature was indeed the key factor [ 33 ].…”