Characterization of Pomegranate (Punica granatum L.) through the Morphoanatomical and Lipid Profile of Seeds for the Valorisation of Italian Accessions

Abstract

Pomegranate produces fruit with high nutritional value. Of particular interest is the woody part of the seed, which influences consumer acceptability and is rich in bioactive components. The aim of this study was to morphoanatomically and biochemically characterize the tegmen of local and commercial pomegranates grown in Italy. SEM and a texturometer were used for morphoanatomical and hardness analysis, respectively, and gravimetric and Soxhlet extraction, as well as a GS-MS instrument, were used for chemical analysis. In addition to the classic morphometric parameters, we described, for the first time, the bundles on pomegranate tegmen, identifying four forms (FAN, TREE, COMB and RAMIFIED); local cultivars showed a higher variability compared to the commercial cultivars. Lignin content showed no correlation with seed strength. We developed a new hierarchical model in which geometric parameters and the resistant volume of the lignified tissue can explain the variability in hardness observed in the tests. Quantitative differences were observed in total lipids and unsaponifiable fractions; in particular, all oils were rich in unsaturated fatty acids. We propose that bundles form as a novel trait for characterization and a new hierarchical model to evaluate the hardness of seeds. The content of fatty acids and other biocompounds in pomegranate seeds can promote their valorization as a resource rather than a waste product.