Materials and Methods

Diglycerol (or polyglycerol-2, PG2, purity >90%, with traces of glycerol, triglycerol, and tetraglycerol) was supplied by Inovyn (United Kingdom), and stearic acid (SA, purity >98%) was supplied by Giomavaro (Italy). All other chemicals and solvents were purchased from Sigma Aldrich, Fluka, Titolchimica (Italy). Polyglycerol-2 stearic acid esters (PG2SAEs) produced through acid-catalyzed esterification (C) by Res Novare (Italy) were used as reference samples. The immobilized lipase from Candida antarctica type B, Novozym 435 (declared enzymatic activity: 5000 LU g^–1), was kindly provided by Novozymes (Denmark). Silica gel 60, 40–63 μm (Merck), was used for flash column chromatography. Analytical thin-layer chromatography (TLC) was performed on silica gel F₂₅₄ precoated aluminum sheets (0.2 mm layer, Merck, Germany); components were detected by spraying with a Ce(SO₄)₂/(NH₄)₆Mo₇O₂₄ × 4H₂O solution, followed by heating at 150 °C. Electrospray ionization mass spectroscopy (ESI-MS) analysis was recorded on a Thermo Finnigan LCQ Advantage spectrometer (United Kingdom).