Relating consumer preferences to textural attributes of cooked beans: Development of an industrial protocol and microstructural observations

The effects of temperature, duration of cooking and different cooking media (salt solutions) on bean-texture attributes were evaluated by response surface methodology. Sensory evaluation and scanning electron microscopy (SEM) were also carried out to clarify the properties of cooked beans. The sensory evaluation results showed that consumers most prefer beans with a soft texture. A 24 full-factorial central composite design (CCD) was used to optimize the process conditions. For each response, a second-order polynomial model was developed using multiple linear regression analysis. Applying the desirability function method, the most suitable combination of process conditions to obtain the texture found most acceptable were a cooking temperature of 75 °C, a cooking time of 63 min, NaCl concentration of 1.88 g/l and CaCl2 concentration of 0.12 g/l. RSM analysis indicated good correlation between experimental and predicted values. SEM studies of cooked bean tissues further confirmed that cell-wall separation was mainly the result of pectin solubilization and middle lamella dissolution. An important finding obtained in this study was determining the optimum salt concentration needed to soften the grain in a minimum period of time; this is important from an economic as well as from an industrial point of view.