Sugar content and profile of Zucchella and Ramassin, local Italian plums used for no-added sugar traditional jam manufacturing

Plums are produced from a wide range of Prunus species, cultivars and landraces, characterised by highly variable pomological, sensory and compositional traits. Sweetness is an important attribute of plums and derived products. A high sugar content characterises Prunus domestica fruits, which are processed into jams, dried prunes, juices, beyond being eaten fresh. The functional properties related to fibre content are preserved in processed jams, whose potential dietary and health benefits can however be decreased because of the generally high level of added sugars. The fruits of some local plum varieties are often traditionally processed by no- or low-sugar addition, because of their natural sweetness. Among them, Zucchella (Prunus domestica L.), grown on small areas of Emilia region (North East of Italy) and Ramassin (Prunus domestica subsp. insititia (L.) Bonnier & Layens), traditionally cultivated in Piedmont region (North West of Italy) are ancient genotypes locally exploited for their interesting characteristics. Pomological traits, soluble solids, sugar and organic acid content and profile of Zucchella and Ramassin plums collected at full ripening were analysed. The two cultivars showed a different sugar and organic acid profile. Zucchella plums were characterised by a high sorbitol content, amounting at 16% of total sugars, compared to 4% in Ramassin plums. Sorbitol is a sugar alcohol with properties of natural laxative and not subject to non-enzymatic browning that causes sugars and amino acids degradation. Glucose was, on average, the most abundant sugar, (38% of total sugars), whereas sucrose accounted for 40% and 20% of total sugars in Ramassin and Zucchella, respectively. The most abundant organic acids were malic and quinic in Zucchella plums, whereas succinic and quinic acid characterised Ramassin plums.