Nutritional and antimicrobial properties of tomato by-products as affected by dehydration temperature

The present study focuses on the influence of three different dehydration temperature (i.e., 50, 60, and 70 °C) on both nutritional quality and antimicrobial/antifungal efficacy of tomato peels and seeds (TPS). To this aim, TPS were dehydrated at the three temperatures and then ground into powder. The nutritional quality of TPS was evaluated by measuring the total polyphenolic and flavonoid content, and the antioxidant activity. Fresh by-products were used as the control. Results indicated that dehydration reduced the nutritional quality of by-products. However, the different temperatures did not affect the content in total phenol and flavonoid, neither the antioxidant activity, above all when measured by the ABTS assay. The efficacy of TPS against food spoiling species (i.e., Pseudomonas spp., yeasts, Alyciclobacillus acidoterrestris ) was also assessed. In the case of Pseudomonas spp., the results indicated that TPS were effective in retarding microbial growth, while in the case of yeasts and A. acidoterrestris TPS slightly slowed down the growth kinetics, without any statistically significant differences among samples. The striking feature of the in vitro tests is the evidence that in all cases the three dehydration temperatures did not exert any influence on the efficacy/inefficacy. The productivity of the dehydration process was finally evaluated, considering the time needed to reach 99% of total dehydration. Results demonstrated that productivity increased as the dehydration temperature increased.