Physical and chemical characteristics and lycopene retention of dried tomatoes subjected to different pre-treatments

Abstract

This study evaluated the physical and chemical characteristics (moisture, pH, acidity titratable, soluble solids and color) and lycopene retention in dried tomatoes submitted to different pretreatments. The tomatoes were cut longitudinally and submitted to the osmotic dehydration for 120 minutes. Six osmotic solutions were used with the following concentrations: NaCl 5%, NaCl 10%, NaCl 5% + sucrose 10%, NaCl 10% + sucrose 5%, sucrose 5%, sucrose 10% (w/v), and the osmotic dehydration was conducted with direct application of the solutes (NaCl or mixture of NaCl + sucrose). Soon afterwards the tomatoes were submitted to drying at 65°C for 12 hours. The osmo-convective drying promoted an increase in the level of soluble solids, titratable acidity and reduction of the pH, except for the sucrose solutions, that did not alter the pH of the tomatoes. The ternary solution (NaCl + sucrose), binary (NaCl 10%) and the direct application of the solutes promoted significant moisture reduction in relation to the control. The osmotic solutions only containing sucrose or NaCl 5% presented lycopene retention significantly superior to the other treatments. The use of the osmotic dehydration as pretreatment for drying of the tomato can contribute to accelerate the drying process and to preserve the tomato lycopene level.