Molecular weight distribution of the triacylglycerols of berry seed oils analysed by negative-ion chemical ionization mass spectrometry

Seed oils of 22 northern wild berry species collected in Finland were studied by ammonia negative-ion chemical ionization mass spectrometry using a direct exposure probe for sample introduction. The berries belonging to 13 genera (Vaccinium, Oxycoccus, Arctostaphylos, Empetrum, Hippophae, Chamaepericlymenum, Sambucus, Rosa, Fragaria, Rubus, Sorbus, Prunus and Ribes) represented the most important Scandinavian edible berry species. The mass spectrometric analyses provided information about the different molecular weight species of triacylglycerols and their proportions in the seed oils studied. Triacylglycerols with 54 acyl carbons were the most abundant components in all berry oils (72–97 mol%). The proportions of triacylglycerols with 52 and 56 acyl carbons were only 2–23 mol% and 0–6 mol%, respectively. The results were in good agreement with the fatty acid compositions of the berry seed oils reported elsewhere. The species-specific molecular weight patterns varied from the random fatty acid distribution most clearly in the seed oils of P. padus (P=0.03) and Rubus chamaemorus (P=0.02). Negative-ion chemical ionization mass spectrometry is a useful tool for the screening of triacylglycerol profiles, as shown in the present study. Measurement of the oil or fat authenticity or of the mixing ratios of different oils is one potential application of the fast analytical technique described.