A comparative evaluation of the phenol and lycopene content of tomato by-products subjected to different drying methods

This study is focused on exploring tomato by-products to provide ingredients rich in bioactive compounds with higher functional value through applying innovative techniques (microwave and spiral flash dryer) and conventional techniques (freeze-drying and hot air-drying) to the dehydration of industrial tomato pomace. The effect of the drying method on the bioactive composition of the tomato by-products (phenols, lycopene and soluble dietary fiber) was analyzed. The phenolic composition was determined using a targeted chromatographic approach based on UHPLC-QqQ-MS/MS. Large amounts of naringenin (194.7¿949.4 mg/kg) were detected, together with quercetin, caffeic acid, coumaric acid and 4-hydroxybenzoic acid. Microwave dehydration improved the retention of flavanone-like compounds, especially naringenin, and lycopene, while tomato products dehydrated with Spiral Flash dryer showed higher concentrations of flavonols and phenolic acids. The results showed that the industrial application of drying processes using Spiral Flash, and especially with microwaves, could be promising for producing high added-value ingredients from tomato by-products.The authors are grateful to the technical staff, Cristina Moreta and Miguel Ángel Fernández-Recio, of the Instrumental Analysis Service at the ICVV by their UHPLC-QqQ-MS/MS analytical and technical support in the phenol analysis. This work has been co-financed by the European FEADER funds, the Ministry of Agriculture and Food of Spain and the Government of La Rioja, through the project funded in call PDR “plusPRODUCT: By-product valorization and development of the Circular Economy in the Agrifood Industry” (reference: 23M/20) and pre-doctoral grants