Evaluation of Tomato (Lycopersicon esculentum P. Mill.) By-product Extracts Obtained by Different Extraction Methods as Exploitation Strategy of High-Value Polyphenols

Abstract

Tomato has antioxidant properties from polyphenols, but tomato by-products have been little studied, which can have significant added value for the pharmaceutical or food industry. Several polyphenol extraction processes cause variability in detected compounds and their concentrations, making it necessary to characterize each method for a suitable exploitation strategy. In this research, tomato by-products were first dried using an oven or a dehydrator, resulting in oven-dried extracts with higher polyphenols than dehydrator-dried ones. Four solid–liquid methods by Soxhlet extraction (SOX), stirring extraction (SE), ultrasound-assisted extraction (UAE), and microwave-assisted extraction (MAE) were developed and employed for obtaining oven-dried extracts. Suitable and green extraction processes were carried out using different ethanol/water extractants, sample–extractant ratios, extraction times, and exposing conditions to physical energies, depending on optimal conditions calculated by multivariate optimization. Total polyphenols and antioxidant capacity indices and gallic acid, caffeic acid, chlorogenic acid, quercetin, and kaempferol concentrations were determined in extracts. Principal component analysis found an excellent relationship between caffeic acid and total polyphenol index and gallic acid and antioxidant capacity. SE and UAE extracted more amounts of all polyphenols, but UAE was exhaustive at only 5 min. MAE was also fast, completing extraction at 20 min, but reducing phenol concentration by around 30% than SE and UAE. SOX showed the lowest indices and phenol concentrations after a long extraction time. To sum up, the present study evidences the importance of the extraction method on the quality and quantity of polyphenols in tomato by-product extracts.Graphical