Predictive modelling of vegetable firmness after thermal pre-treatments and steaming

• Softening of vegetables during steaming was modelled using a temperature dependent fractional conversion model.
• Resistance towards softening can be enhanced by thermal pre-treatments.
• A predictive model for increasing the softening resistance was developed.
• Multi-criteria optimisation of vegetable quality is enabled by modelling the effects of pre-treatment time and temperature.

Texture is an important product property that strongly affects the quality evaluation of processed vegetables by consumers. The rate of texture decrease is dependent on the processing temperature and the type of vegetable. A large data set on instrumental texture measurements of carrot and broccoli was produced with different time–temperature combinations for steaming the vegetables. This data set was fitted with a fractional conversion model to describe the kinetics of texture change. Pre-treating the vegetables by steaming at 50–80 °C can increase the resistance towards softening in a subsequent steaming process. The effect of time and temperature of the thermal pre-treatment on the rate constant of softening during subsequent steaming has been evaluated. A response surface two factor interaction model could well describe this effect. Pre-treatments enable more flexibility to optimise several product properties like health, texture and colour. The predictive model presented here is a valuable tool for this multi-criteria optimisation.Industrial relevanceA model to describe the softening of vegetable texture during steaming is presented, and the effect of pre-treatment conditions on the reduction of the subsequent softening rate is included in the model. With this model vegetable texture can be improved by predicting the optimal time and temperature of the pre-treatment. This model can be integrated into a multi-criteria optimization approach to improve other quality attributes and still give a desired texture.