(29a) Influence of Citric Acid Pretreatment and Different Temperatures on the Convective Drying of Banana

Banana is one of the most consumed fruits in the world, but, due to its high perishability, postharvest loss rates are high. For this reason, the search for techniques that aim to prolong its shelf life and reduce losses is critical. By reducing food moisture content, reducing the amount of water available for microbial proliferation and the occurrence of chemical and enzymatic reactions, drying is seen as an alternative to increase the shelf life of fruits and vegetables. However, drying some materials is a challenge for researchers, due to their sensitive nature and diversity in material properties, requiring further studies. Conventional drying methods that use hot air for a long time affect the physicochemical and nutritional quality of the product, and have high energy expenditure. To optimize the drying process, one of the ways to increase the mass transfer rate occurs through the use of pretreatments. The use of organic acids as a pretreatment is still little explored, mainly if considered to improve mass transfer through the action of these acids on superficial lignocellulosic compounds. Therefore, there is still a need to understand, describe and improve the mechanisms about the use of these pretreatments, which also depends on the processing conditions used. This work aimed to evaluate the influence of citric acid in the pretreatment and different temperatures on the convective drying kinetics of banana (Musa paradisiaca) and its quality parameters (water activity and color). For the pretreatment step, the samples were immersed in an aqueous solution of citric acid (2% m/v) for different times (10, 20 and 30 min). Convective drying of the bananas with and without pretreatment was performed on a fixed bed dryer at 60 and 70 °C and 2 m/s air velocity. For the adjustment of experimental drying data, five empirical models (Henderson and Pabis, Logarithm, Wang and Singh, Simple Exponential, Two-terms Exponential) were used. Pretreated samples showed a higher reduction in drying time, mainly when the acid exposure time was higher and when drying was performed at 70 °C. The Two-terms Exponential model had the best fit to the experimental data. Regarding the studied quality parameters, the samples submitted to acid pretreatment presented water activity values less than 0.6. Also, the dried pretreated bananas presented lower color changes. The results showed that the pretreatment with citric acid could be a viable alternative to reduce the drying time and the impacts caused by the process.