Integration of design of experiment, surface response methodology, and multilayer validation to predict the effect of blanching on color of tomato juice

Abstract

Response surface methodology was used to develop models to predict the effect of tomato cultivar, juice pH, blanching temperature, and time on color change of tomato juice after blanching. The juice from three tomato cultivars with adjusted pH levels ranging from 3.9 to 4.6 were blanched at temperatures from 60 to 100 °C for 1–5 min using the central composite design (CCD). The color change was assessed by calculating the redness (a/b) and total color change (ΔE) after measuring the Hunter L, a, and b values. Developed models for both redness and ΔE were significant (p < .0001) with satisfactory coefficient of determination (R² = .99 and .97) and low coefficient of variation (CV% = 1.89 and 7.23), respectively. Multilevel validation that was implemented revealed that the variation between the predicted and experimental values obtained for redness and ΔE were within the acceptable error range of 7.3 and 22.4%, respectively. PRACTICAL APPLICATIONS: Thermal blanching is an essential pretreatment carried out extensively in tomato juice processing industry. Scientific evidence and experience show that fruit variety or cultivar and the exact blanching conditions can affect either positively or negatively the tomato juice color, the most important quality attribute of the product. Therefore, optimization of blanching conditions as performed using the current thermal technology in order to obtain desired color properties is still very important. In this study the impact of tomato cultivar, juice pH, and blanching conditions (temperature and time) on the color of tomato juice after blanching was evaluated and models have been developed that predict the redness and color change after processing. The models were incorporated into an access web tool we developed that could be beneficial in optimizing the processing conditions for a particular tomato cultivar in an industrial environment.