ORIGINAL ARTICLE Glycidols Esters, 2-Chloropropane-1,3-Diols, and 3-Chloropropane-1,2-Diols Contents in Real Olive Oil Samples and their Relation with Diacylglycerols Angelo Cichelli 1 · Ylenia Riciputi 2 · Lorenzo Cerretani 3 · Maria F. Caboni 2 · Nicola d’Alessandro 4 Received: 30 November 2018 / Revised: 24 September 2019 / Accepted: 6 October 2019 © 2019 AOCS Abstract A series of authentic virgin, refined, and mix- tures 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, dem- onstrating 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 correla- tion 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 proba- bility and the steric effect of the SN2 formation mecha- nism, 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 con- trol, 3-MCPD is more stable). Keywords Olive oil  Glycidol  3-Chloropropane- 1,2-diol  Diacylglycerol  Pomace olive oil  Lampante olive oil J Am Oil Chem Soc (2019). Abbreviations 2-MCPD 2-chloropropane-1,3-diol. 3-MCPD 3-chloropropane-1,2-diol DAG diacylglycerol EVOO extra virgin olive oil FA fatty acid GE glycidyl esters MAG monoacylglycerol RLOO refined from crude lampante olive oil RPOO refined from crude pomace olive oil TAG triacylglycerol VOO virgin olive oil Introduction Olive oils extracted from fresh and healthy olive fruits (Olea europaea L.), properly processed, and adequately stored are characterized by a typical and pleasant flavor and unique taste. Their flavor is characteristic and markedly dif- ferent from those of other edible fats and oils that undergo refining, which leads to the loss of most minor components (mainly volatile compounds). Once it is stated that any oil extracted by mechanical means from olive fruit is a virgin oil, the quality can be * Nicola d’Alessandro nicola.dalessandro@unich.it 1 Department of Medical, Oral and Biotechnological Science, University “G. d’Annunzio” of Chieti-Pescara, Via dei Vestini, 66100 Chieti Scalo, Chieti, Italy 2 Department of Agricultural and Food Technology Science, University of Bologna, Viale Fanin 44, 40127 Bologna, Italy 3 Salpa S.c.a.r.l., Via Adriatica, 554, 64026 Roseto degli Abruzzi, Teramo, Italy 4 Department of Engineering and Geology, University “G. d’Annunzio” of Chieti-Pescara, Via dei Vestini, 66100 Chieti Scalo, Chieti, Italy J Am Oil Chem Soc (2019) DOI 10.1002/aocs.12302 J Am Oil Chem Soc (2019)