Relationships between quality of crude and refined edible oils based on quantitation of minor glyceridic compounds

The relationships between crude and refined oils are examined by quantitation of minor glyceridic compounds, namely, oxidized triglyceride monomers, dimers and diglycerides, associated with oil quality. Particularly, two groups of compounds, i.e. oxidized triglyceride monomers and diglycerides, are of especial interest as they are indicative of oxidative and hydrolytic alterations, respectively. Olive, sunflower and soybean oils differing in initial quality, as evaluated by classical indices and levels of undesirable minor compounds, were subjected to physical and alkali refining in a laboratory system. In all assays, results indicated that amounts of oxidized triglyceride monomers and diglycerides in refined oils remained close to those found in the starting crude oils. Triglyceride dimers were the only group of compounds showing a significant increase, which was dependent on fatty acid composition and initial quality of crude oils. The main conclusion is that quantitation of minor glyceridic compounds in refined oils not only offers a new possibility for quality evalution but also allows the crude oils to be characterised by the presence of markers of oxidative and hydrolytic alterations.