HRMAS-nuclear magnetic resonance spectroscopy characterization of tomato “flavor varieties” from Almería (Spain)

1H HRMAS NMR spectroscopy has been applied to investigate differences at a metabolic level between “flavor varieties” of high quality tomatoes marketed as Protected Geographical Indication from Almería (Spain). The varieties studied include the non-hybrid Raf tomato, one of the most tasteful commercial tomatoes that is traditionally grown in this Spanish region, together with other two hybrid varieties of commercial names Rambo and Zayno. Standard quality parameters were poorly reliable for establishing specific correlations with a given variety. In contrast, 1H HRMAS NMR spectroscopy, in combination with principal component analysis (PCA) and assigned signal analysis (ASA) provided a clear differentiation between varieties as a function of the ripening process and revealed the existence of variety-dependent relationships between external appearance and metabolic content. γ-Aminobutyric acid (GABA) is envisioned as a good marker for monitoring the ripening process. The content in other taste-relevant metabolites (fructose and organic acids) proved to be variety-dependent. The results show a preferential accumulation of citric acid and fructose in Rambo and Raf varieties, respectively. Raf fruits are characterized by high fructose to glucose and fructose to citric acid ratios. The content of malic acid during ripening also remains high for Raf tomato. These combined features are responsible of the unique characteristic and exceptional taste of this traditional line of tomato.

► 1H HRMAS NMR is applied to metabolic characterization of tomato flavor varieties. ► PCA combined with assigned signal analysis distinguishes varieties. ► Ripening process is variety-dependent. ► GABA is a good marker for following the ripening process. ► The content in fructose and organic acids is variety-dependent.