No abstract

Due to the importance of hydration stage for parboiling, related studies are insufficiently addressed in the literature. The objective of this study was to model the moisture absorption kinetics of paddy rice, as well as estimate the thermodynamic properties involved in the hydration. The observed mass transfer in the process was directly influenced by the temperature of the system, showing changes in absorption capacity over time. The models addressed allowed satisfactorily describing the moisture gain under various thermal conditions. Particularly, the model based on Fick's second law best represented the experimental data. The effective diffusion coefficient was adjusted to an Arrhenius equation and a new model was generated, capable of describing hydration. The coefficient presented positive dependence with the temperature increase and allowed the determination of different forms of process energy. It was concluded that the hydration of the rice in the parboiling process is nonspontaneous and exothermic. Practical applications This study allowed characterizing the moisture transfer in the hydration stage of the parboiling process, exploring the time and temperature relationship. From these data, mathematical modeling was used as a quality tool, guaranteeing for the parboiling industries control and optimization of the process in a cheap and easy way. In addition, this study presented relevant information on the thermodynamic properties, which made it possible to understand the different forms of energies and phenomena involved. This information can help, in a practical way, in the elaboration of industrial projects aimed at the parboiling of rice.

No abstract

The conventional parboiling process decreases the total phenolic compounds (TPC) and the antioxidant activity (AA) of rice. In order to change this nutritional disadvantage, in this research we have proposed an unusual solution. Here, we added grape pomace (agro-industrial waste) in the process during the parboiling as a source of bioactive compounds (BC). An increase in the concentrations of TPC, flavonoids anthocyanins and antioxidant activity was found. Moreover, there was slightly change in the final colour of the rice (which tended towards red) in addition to added proline (NMR spectra), which is an amino acid that is characteristic of grapes. Therefore, we concluded that it is possible to improve the functionality of parboiled rice with the addition of grape pomace, besides promoting the valorisation and use of an agro-industrial waste rich in secondary metabolites.