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.