Amino acids profile and nutritional value of processed tomato by-products

Tomato by-products, such as its fresh fruit, contain bioactive compounds with beneficial properties for human health. The analysis of these bioactive compounds provides relevant information that promotes the valorization of these by-products. Amino acids are considered to be compounds with a high nutritional value.

In this work, the amino acid (aa) profiles and nutritional values of processed tomato by-products, which were subjected to one of two dehydration methods—at 60 °C in a hot air circulation oven (OD) or freeze-drying (FD)—were analyzed using HPLC-DAD-FLD and AOAC, respectively. In total, 20 protein and 1 non-protein amino acids (γ-aminobutyric acid, GABA) were identified in the tomato by-products.

The co-elution of some compounds was observed, namely Asp+Glu, GABA+Pro, and Ile+Leu. Asp+Glu was the most abundant, followed by Gln, Arg, Tyr, and GABA+Pro. The OD treatment reduced the percentage of Gln (14.68%), Gly (10.88%), GABA+Pro (14.40%), Met (10.00%), Val (8.80%), Phe (13.07%), Trp (10.43%), Ile+Leu (11.05%), His (10.64%), and Lys (17.91%), while it increased that of Tyr (9.08%) compared to the FD method, in which no significant differences were observed in the other amino acids. Nevertheless, the OD treatment showed a higher percentage of essential amino acids (21.8%) compared to the FD treatment (20.5%). The decreased aa content in the OD treatment may be attributed to the temperature effect on the drying process. The fiber, carbohydrate, protein, and fat content, which were determined for the nutritional value, did not show significant differences between dehydration treatments.

The results contribute to knowledge about the composition of by-products from tomato processing industries. Although lower values ​​were observed for some amino acids in the oven drying treatment, there were no differences in nutritional value, resulting in a more cost-effective option for the dehydration of tomato by-products as an economic source of phytochemical compounds, providing added value to biotechnology-based industries.