Assessing the Relationship Between the Phenolic Content and Elemental Composition of Grape (Vitis vinifera L.) Stems

There is a growing interest in the application of grape stems as source of nutrients and bioactive compounds, for its use in the cosmetic, pharmaceutical and food industries. The main goal of this study was to determine the content of essential minerals, toxic metals and phenolic compounds present in grape stems, not only to understand if this by-product can be applied in the development of new products as a source of mineral nutrients, but also to understand the possibility of existing a relationship between all these parameters. The results demonstrated that this by-product presented a high content of essential minerals, being the most abundant Na, Mg, Ca, and K, ranging from 0.65, 1.34, and 1.41 to 24.45 g/kg DW, respectively, on average, as well as phenolic contents ranging from 30.91 ± 0.73 to 96.12 ± 8.14 mg GAE/g DW. In fact, stems are richer in phenolic compounds and minerals, in some cases higher than some food matrices consumed in our diet, whereby this by-product can be a good bet in the production of value added products. Furthermore, the principal component analysis showed a relationship between some elements (NI, Na, Al, As, Cd, and Pb) and the higher/lowest concentration of phenolics.