Improvement the firmness of thermal treated black cherry tomatoes (Solanum lycopersicum cv. OG) by low-temperature blanching in calcium chloride solution

Abstract

The objective of this study was to investigate the effects of low-temperature blanching in calcium chloride (CaCl2) solution before high-temperature processing (90oC for 1 min) on physicochemical properties related to the texture (total calcium content, pectin methylesterase (PME) activity, and firmness) of black cherry tomatoes (Solanum lycopersicum cv. OG) and to determine the optimum conditions to provide the fruits with the highest firmness. Response Surface Methodology (RSM) was applied to design the experiment with three factors of blanching temperature (52 to 68oC), blanching time (12 to 28 mins) and CaCl2 solution concentration (1.2 to 2.8% w/v). A sample without low-temperature treatment was taken as a control. It was found that the blanching of tomatoes at low-temperatures resulted in higher total calcium content and PME activity in tissue after the treatment, and therefore improved the firmness of fruits after high-temperature processing. The highest firmness of treated tomatoes (566.21 g force) was estimated at blanching temperature of 62.05oC for 23.09 mins in 2.08% CaCl2 solution compared to the control which was blanched at high temperature (218 g force). Under these optimized conditions, the experimental responses (total calcium content, PME activity, and firmness) showed a close agreement with the predicted values.