Impact of Industrial Drying Processes on Phenolic Compounds and Lycopene in Tomato By-Products

In the context of the circular economy, the tomato industrial processing chain, which annually generates large amounts of waste, presents a potential for obtaining bioactive compounds. This study is focused on exploring the tomato by-products to provide ingredients rich in bioactive compounds with higher functional value through different dehydration processes, avoiding unnecessary and expensive extraction procedures. This research describes the application of 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 flavanone (194.7-949.4 mg/Kg) were found in tomato by-products, together with such other phenolic compounds as quercetin, caffeic, coumaric and 4-hydroxybenzoic acids. 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 that showed 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.